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          <link:loc xlink:type="locator" xlink:href="tslx-20260331.xsd#tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveMember" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveMember"/>
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          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany" xlink:label="dei_EntityEmergingGrowthCompany"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20260331.xsd#tslx_MediaAdvertisingPrintingAndPublishingSectorMember" xlink:label="tslx_MediaAdvertisingPrintingAndPublishingSectorMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_SE" xlink:label="country_SE"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20260331.xsd#tslx_EuroInterbankOfferRateEURIBORMember" xlink:label="tslx_EuroInterbankOfferRateEURIBORMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20260331.xsd#tslx_SterlingOvernightIndexAverageRateSONIAMember" xlink:label="tslx_SterlingOvernightIndexAverageRateSONIAMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20260331.xsd#tslx_NorwegianInterbankOfferedRateNIBORMember" xlink:label="tslx_NorwegianInterbankOfferedRateNIBORMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20260331.xsd#tslx_StockholmInterbankOfferedRateSTIBORMember" xlink:label="tslx_StockholmInterbankOfferedRateSTIBORMember"/>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity investment</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Equity Securities, FV-NI, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Ownership interest in members' equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q2SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q2 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q2SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 Q2 supplemental dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q2SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q2 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Four</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured Product Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Proceeds from Short-Term Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Short-Term Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Borrowings on debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIssuerNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Issuer Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PharmaceuticalsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pharmaceuticals.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PharmaceuticalsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pharmaceuticals [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PharmaceuticalsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pharmaceuticals</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Incorporation, State or Country Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Incorporation, State or Country Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total unrealized and realized gains (losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss), Investment and Derivative, Operating, and Foreign Currency Transaction, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Net Unrealized and Realized Gains (Losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HumanResourceSupportServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Human Resource Support Services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HumanResourceSupportServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Human Resource Support Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HumanResourceSupportServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Human Resource Support Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IbisIntermediateCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ibis Intermediate Co.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IbisIntermediateCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ibis Intermediate Co [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IbisIntermediateCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ibis Intermediate Co.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of All Pre Incentive Fee Net Investment Income After Catch Up Achieved</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of all pre-Incentive Fee net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanDueMayTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL FILO Term Loan due 5/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanDueMayTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ABL FILO Term Loan Due May Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanDueMayTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">A B L F I L O Term Loan Due May Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Current Reporting Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Current Reporting Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCommitment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Commitment, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCommitment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Commitment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCommitment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other commitments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Financing Receivable [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Financing Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInIncentiveFeePayableCapitalGainBased_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Incentive Fee Payable, Capital-Gain-Based</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInIncentiveFeePayableCapitalGainBased_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net capital gains accrued to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInIncentiveFeePayableCapitalGainBased_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Incentive fees on net capital gains accrued to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Revolving Loan due 4/2025</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan April Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableAmountPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Amount Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableAmountPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialServicesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Services Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialServicesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialServicesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Diversified Financial Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 2</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 2 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 6/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due June Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due june two thousand twenty five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q1SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q1 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q1SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 Q1 supplemental dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q1SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q1 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Disposition of Investment, Operating Activity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Repayments on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Financial Highlights [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary Of Financial Highlights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common shares, authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAffiliatedIssuerNoncontrolledMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-controlled, Affiliated Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAffiliatedIssuerNoncontrolledMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Affiliated Issuer, Noncontrolled [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CopperBidcoLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Copper Bidco, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CopperBidcoLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Copper Bidco L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CopperBidcoLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Copper Bidco, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassATwoUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Class A-2 Units.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassATwoUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class A Two Units [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassATwoUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class A-2 Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Document Fiscal Period Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Period Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Stated interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Interest Rate, Stated Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyThreeOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due December two thousand twenty three one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyThreeOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Three One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyThreeOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan($22,507par,due12/2023)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingStandardsUpdate202309Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Standards Update 2023-09 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingStandardsUpdate202309Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ASU 2023-09</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Shell Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Shell Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MerativeLPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Merative L.P.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MerativeLPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Merative L.P. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MerativeLPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Merative L.P.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BearOpCoLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Bear OpCo, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BearOpCoLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Bear Op Co L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BearOpCoLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Bear OpCo, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Convertible Debt [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Convertible Note</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segment Reporting</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash and Cash Equivalents, at Carrying Value, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and cash equivalents (restricted cash of $28,072 and $16,727, respectively)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Cash and cash equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CrunchtimeInformationSystemsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">CrunchTime Information Systems, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CrunchtimeInformationSystemsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">CrunchTime Information Systems, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CrunchtimeInformationSystemsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">CrunchTime Information Systems, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel">Total Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Net Assets, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Net Assets, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total return based on market value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total Return Based On Market Value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Return Based On Market Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeePayableIncomeBased_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fee Payable, Income-Based</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeePayableIncomeBased_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net investment income payable to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyThreeOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due September Two Thousand Twenty Three one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyThreeOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Three One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyThreeOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($5,000 par, Due 9/2023)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common stock, shares issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common shares, issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsDeclaredDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsDeclaredDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividends declared during the period.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsDeclaredDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Declared During The Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsDeclaredDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends declared during the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolver.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolver [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2026Q1BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2026 Q1 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2026Q1BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2026 Q1 base dividends member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2026Q1BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2026 Q1 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeApproachValuationTechniqueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation, Income Approach [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeApproachValuationTechniqueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Approach</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Investment Income (Loss) from Operations, Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand thirty notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2030 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Thirty Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BanyanSoftwareHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Banyan Software Holdings LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BanyanSoftwareHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Banyan Software Holdings LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BanyanSoftwareHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Banyan Software Holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIdentifierAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Identifier [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyTotalReturnMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Total Return, Market Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyTotalReturnMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total return based on market value with reinvestment of dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyNineteenConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Nineteen Convertible Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyNineteenConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty Nineteen Convertible Notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyNineteenConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2019 Convertible Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LithiumTechnologiesLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lithium Technologies, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LithiumTechnologiesLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lithium Technologies L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LithiumTechnologiesLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lithium Technologies, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrant [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 4/2036</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due April Two Thousand Thirty Six One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured Product Due April Two Thousand Thirty Six One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Filer Category</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Filer Category</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrganizationAndBasisOfPresentationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization and Basis of Presentation [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrganizationAndBasisOfPresentationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Organization and Basis of Presentation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OriginalIssueDiscountNetOfAccretion_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Original issue discount, net of accretion</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OriginalIssueDiscountNetOfAccretion_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Original issue discount, net of accretion.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OriginalIssueDiscountNetOfAccretion_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Original Issue Discount Net Of Accretion</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityOwnershipVotingPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Ownership Voting Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityOwnershipVotingPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity ownership voting percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityOwnershipVotingPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Voting percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities and Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Liabilities and Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesByIndustryAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Industry Sector [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesByIndustryAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Industry Sector</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DyeDurhamLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dye &amp; Durham, Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DyeDurhamLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dye Durham Ltd [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DyeDurhamLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dye Durham Ltd</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2029 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Nine Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty nine notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Future Realized Capital Gains Prior to April 1, 2014</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Future Realized Capital Gains Prior to April First Two Thousand Fourteen [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Future realized capital gains prior to April first two thousand fourteen.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of all remaining pre-incentive fee net investment income quarterly.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of All Remaining Pre Incentive Fee Net Investment Income Quarterly</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of all remaining pre-Incentive Fee net investment income quarterly</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityDistributionAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Distribution Agreement Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityDistributionAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity distribution agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityDistributionAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Distribution Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassAOneUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Class A-1 units.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassAOneUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class A One Units [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassAOneUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class A-1 Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienSecuredNoteDueJulyTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Secured Note due 7/2023</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienSecuredNoteDueJulyTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Secured Note Due July Two Thousand Twenty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienSecuredNoteDueJulyTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien secured note due july two thousand twenty three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAggregatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Security Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAggregatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of pre-incentive fee net investment income payable after hurdle rate reached and catch-up achieved.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Pre Incentive Fee Net Investment Income Payable After Hurdle Rate Reached And Catch Up Achieved</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of pre-Incentive Fee net investment income payable in any quarter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ShiftmoveGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Shiftmove gmbH.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ShiftmoveGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shiftmove GmbH [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ShiftmoveGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shiftmove GmbH</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ExtinguishmentOfDebtAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Extinguishment of Debt, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ExtinguishmentOfDebtAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Extinguishment of debt, amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares issued, price per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Issued, Price Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PledgedStatusAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pledged Status [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PledgedStatusAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pledged Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleSeniorNotesDueTwentyNineteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Convertible Senior Notes Due Twenty Nineteen [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleSeniorNotesDueTwentyNineteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Convertible Senior Notes Due Twenty Nineteen.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleSeniorNotesDueTwentyNineteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Convertible Senior Notes Due 2019 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AzuriteIntermediateHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Azurite Intermediate Holdings, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AzuriteIntermediateHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Azurite Intermediate Holdings, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AzuriteIntermediateHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Azurite Intermediate Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfContributedCapitalAndUnfundedCommitmentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Contributed Capital And Unfunded Commitments Table Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfContributedCapitalAndUnfundedCommitmentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of contributed capital and unfunded commitments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfContributedCapitalAndUnfundedCommitmentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Contributed Capital and Unfunded Commitments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due October two thousand twenty six two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Six Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($46,948 par, due 10/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Taxes Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Excise and other taxes paid during the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 7/2031</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due July Two Thousand Thirty One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due July Two Thousand Thirty One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxAuthorityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Jurisdiction [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxAuthorityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Tax Authority</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due April Two Thousand Twenty Seven.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($45,000 par, Due 4/2027)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OxfordSquareCapitalCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Oxford Square Capital Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OxfordSquareCapitalCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Oxford Square Capital Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OxfordSquareCapitalCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Oxford Square Capital Corp</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_SegmentGeographicalDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Geographical [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_SegmentGeographicalDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Geographical</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ChemicalsPlasticsAndRubberSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Chemicals, Plastics and Rubber Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ChemicalsPlasticsAndRubberSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Chemicals, plastics and rubber sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ChemicalsPlasticsAndRubberSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Chemicals, Plastics &amp; Rubber</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlstarGroupLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Carlstar Group, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlstarGroupLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Carlstar Group L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlstarGroupLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carlstar Group, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ElectronicsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Electronics</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ElectronicsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Electronics [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ElectronicsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Electronics.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WindRiverCloLtdSeriesTwoThousandEighteenThreeAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Wind River CLO Ltd, Series 2018-3A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WindRiverCloLtdSeriesTwoThousandEighteenThreeAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Wind River Clo Ltd Series Two Thousand Eighteen Three A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WindRiverCloLtdSeriesTwoThousandEighteenThreeAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Wind river Clo Ltd series two thousand eighteen three A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DesignerBrandsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Designer Brands, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DesignerBrandsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Designer Brands Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DesignerBrandsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Designer Brands Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnderlyingAssetClassDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Underlying Asset Class [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnderlyingAssetClassDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Underlying Asset Class</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ForeScoutTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ForeScout Technologies, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ForeScoutTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fore Scout Technologies Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ForeScoutTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ForeScout Technologies Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ForeScoutTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">ForeScout Technologies, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Due from Affiliates, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payable to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverAndEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolver &amp; Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverAndEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolver And Equity [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverAndEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolver and equity.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienNoteDueJuneTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Note due 6/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienNoteDueJuneTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Note Due June Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienNoteDueJuneTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Note Due June Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional paid-in capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid in Capital, Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnRealizedInvestmentGainsLossesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Un-realized investment gains (losses).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnRealizedInvestmentGainsLossesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Un Realized Investment Gains Losses [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnRealizedInvestmentGainsLossesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net change in unrealized gains (losses):</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Issuance Costs, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Issuance Costs, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PageUpPeopleLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PageUp People, Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PageUpPeopleLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Page Up People Ltd [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PageUpPeopleLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PageUp People, Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LucidworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lucidworks, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LucidworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lucidworks Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LucidworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lucidworks, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment owed on principal amount outstanding and accrued interest make whole amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owed On Principal Amount Outstanding And Accrued Interest Make whole Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment Owed On Principal Amount Outstanding And Accrued Interest Make Whole Amount.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueAprilTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Revolving Loan Due 4/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueAprilTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-Lien Revolving Loan Due April Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueAprilTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-Lien Revolving Loan Due April Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 7/2030</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due July Two Thousand Thirty [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due July Two Thousand Thirty.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="currency_GBP_lbl" xlink:role="http://www.xbrl.org/2003/role/label">United Kingdom, Pounds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="currency_GBP_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">GBP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, Dividend Reinvestment Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock issued in connection with dividend reinvestment plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentVariableInterestRateTypeExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Variable Interest Rate, Type [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Significant Accounting Policies [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Significant Accounting Policies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due October Two Thousand Twenty Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 10/2022</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q2BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2024 Q2 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q2BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2024 Q2 base dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q2BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q2 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CurrencyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Currency [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CurrencyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Currency</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AcousticLPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Acoustic, L.P.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AcousticLPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Acoustic L P [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AcousticLPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Acoustic, L.P.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Computation of Basic and Diluted Earnings Per Common Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditPartnersJVLLCJointVentureInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Credit Partners JV, LLC, Joint Venture Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditPartnersJVLLCJointVentureInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured Credit Partners JV, LLC, joint venture investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditPartnersJVLLCJointVentureInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Joint Venture Investments Structured Credit Partners JV, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditPartnersJVLLCJointVentureInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Structured Credit Partners JV, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due June two thousand twenty six two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due June Two Thousand Twenty Six Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($53,522 par, due 6/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GulfStreamMeridianSeriesTwoThousandTwentyOneSixAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gulf Stream Meridian, Series 2021-6A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GulfStreamMeridianSeriesTwoThousandTwentyOneSixAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gulf Stream Meridian Series Two Thousand Twenty One Six A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GulfStreamMeridianSeriesTwoThousandTwentyOneSixAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Gulf stream meridian series two thousand twenty one six A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentUnaffiliatedIssuerMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Unaffiliated Issuer [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentUnaffiliatedIssuerMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-controlled, Non-affiliated Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueDecemberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Convertible Note due 12/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueDecemberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Convertible Note Due December Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueDecemberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Convertible note due december two thousand twenty four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Credit Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Credit Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured credit investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings per common share&#8212;basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInManagementFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Management Fee Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInManagementFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Management fees payable to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 6/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due June Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due June Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLossesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Investment Gains (Losses) [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLossesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized gains (losses):</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoansDueAugustTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loans Due August Two Thousand Twenty Five One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoansDueAugustTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loans Due August Two Thousand Twenty Five One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoansDueAugustTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($41,768 par, due 8/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetValuationWaterfallMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Asset valuation waterfall.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetValuationWaterfallMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Valuation Waterfall [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetValuationWaterfallMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset Valuation Waterfall</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due august two thousand twenty six one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due August Two Thousand Twenty Six One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($5,127 par, due 8/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NoninterestExpenseDirectorsFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Director Fee</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NoninterestExpenseDirectorsFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Directors&#8217; fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Issuance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandAndTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First Lien Revolving Loan Due 10/2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandAndTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan Due October Two Thousand and Twenty Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandAndTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien revolving loan due 10/2027.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyTotalReturn_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Total Return</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyTotalReturn_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total return based on net asset value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevolvingCreditFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevolvingCreditFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustments to reconcile increase (decrease) in net assets resulting from operations to net cash provided by (used in) operating activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingAfterTaxAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Gain (Loss), Investment, Derivative, and Foreign Currency Transaction, Operating, after Tax [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingAfterTaxAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized gains (losses):</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueJulyTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan due 7/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueJulyTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan One Due July Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueJulyTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan One Due July Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingDesignationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hedging Designation [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingDesignationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hedging Designation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fee Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JointVentureInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Joint Venture Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JointVentureInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Joint venture investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JointVentureInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Joint Venture Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Record Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Date of Record</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends record date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseRatioBeforeIncentiveAllocation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Expense Ratio before Incentive Allocation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseRatioBeforeIncentiveAllocation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ratio of net expenses to average net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VerdadResourcesIntermediateLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Verdad Resources Intermediate LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VerdadResourcesIntermediateLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Verdad Resources Intermediate L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VerdadResourcesIntermediateLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Verdad Resources Intermediate L L C</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayableFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Notes Payable, Fair Value Disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayableFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DomesticCountryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Domestic Tax Jurisdiction [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DomesticCountryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">U.S. Federal Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HornetsecurityHoldingGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hornetsecurity Holding GmbH</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HornetsecurityHoldingGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hornetsecurity Holding GMBH Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HornetsecurityHoldingGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hornetsecurity Holding GMBH.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Tax Basis, Unrealized Gain</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross unrealized gain</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Estimated gross unrealized gains on tax cost investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Estimated gross unrealized gains on tax cost investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due November two thousand twenty six two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due November Two Thousand Twenty Six Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($35,000 par, due 11/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeniorSecuredLoans_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Senior secured loans</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeniorSecuredLoans_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Senior Secured Loans</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeniorSecuredLoans_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Senior secured loans.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of weighted cumulative realized capital gains less cumulative realized capital losses and unrealized capital losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Weighted Cumulative Realized Capital Gains Less Realized Capital Losses and Unrealized Capital Losses Through March 31 2014 Hurdle Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of weighted cumulative realized capital gains less realized capital losses and unrealized capital losses through March 31, 2014 hurdle rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total increase/(decrease) in net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Net Asset Value, Per Share, Period Increase (Decrease)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total increase/(decrease) in net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of components of interest expense.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Components Of Interest Expense [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Components of Interest Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ResmanLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ResMan, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ResmanLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ResMan, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ResmanLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ResMan, llc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Standards Update [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($28,878 par, Due 5/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-lien Loan Due May Two Thousand Twenty Four Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due May Two Thousand Twenty Four Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MauricesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maurices, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MauricesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maurices Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MauricesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Maurices, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Delayed Draw</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Delayed draw.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueFebruaryTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 2/2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueFebruaryTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due February Two Thousand Twenty Seven.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueFebruaryTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due February Two Thousand Twenty Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Changes in Fair Value of Investments Using Level 3 Inputs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PayScaleHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PayScale Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PayScaleHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pay Scale Holdings Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PayScaleHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PayScale Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityOfferingExpensesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity offering expenses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityOfferingExpensesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Offering Expenses [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityOfferingExpensesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Offering Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Small Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Small Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($12,000 par, due 3/2029)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-lien Loan Due March Two Thousand Twenty Nine [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due March Two Thousand Twenty Nine.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingDesignationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hedging Designation [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingDesignationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hedging Designation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OctagonInvestmentPartnersThirtyEightLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Octagon Investment Partners Thirty Eight Ltd, Series Two Thousand Eighteen One A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OctagonInvestmentPartnersThirtyEightLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Octagon investment partners thirty eight ltd, series two thousand eighteen one A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MarketApproachValuationTechniqueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation, Market Approach [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MarketApproachValuationTechniqueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Market Multiple</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total distributable earnings - book basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings (Accumulated Deficit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Distributable earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 9/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due september two thousand twenty five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesIndustryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Industry Sector [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesIndustryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Industry Sector</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecuredBorrowings_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Secured Borrowings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecuredBorrowings_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Secured borrowings.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecuredBorrowings_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Secured borrowings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanDueSeptemberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL FILO term loan due 9/2022</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanDueSeptemberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ABL FILO Term Loan Due September Two Thousand Twenty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanDueSeptemberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ABL FILO term loan due september two thousand twenty two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 12/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan One Due December Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan One Due December Two Thousand Twenty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SixthStreetSpecialtyLendingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sixth Street Specialty Lending, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SixthStreetSpecialtyLendingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sixth Street Specialty Lending, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SixthStreetSpecialtyLendingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sixth Street Specialty Lending, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EnergySectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Energy Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EnergySectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Energy: Electricity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RMCFIVCIVXXXVLPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">RMCF IV CIV XXXV, LP.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RMCFIVCIVXXXVLPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">R M C F I V C I V X X X V L P [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RMCFIVCIVXXXVLPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">RMCF IV CIV XXXV, LP.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PingIdentityHoldingCorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ping Identity Holding Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PingIdentityHoldingCorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ping Identity Holding Corporation [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PingIdentityHoldingCorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ping identity holding corporation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Convertible note.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Convertible Note [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Convertible Note</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization, Consolidation and Presentation of Financial Statements [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDividends_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Payments of Dividends, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDividends_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments of Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDividends_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Dividends paid to stockholders</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingAfterTaxAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net change in unrealized gains (losses):</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingAfterTaxAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain (Loss), Investment, Derivative, and Foreign Currency Transaction, Operating, after Tax [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksRelatedToOurSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Risks Related to Our Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksRelatedToOurSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Risks Related to Our Securities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonClassAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class A Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonClassAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Class A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KahuaIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Kahua, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KahuaIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Kahua Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KahuaIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Kahua inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AffiliatedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Affiliated</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AffiliatedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Affiliated [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AffiliatedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Affiliated.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Amendment Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amendment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingencies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loss Contingencies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due April two thousand twenty six one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Six One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan($17,018par,due4/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common units.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Units [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VoyaCloLtdSeries20183AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Voya CLO Ltd, Series 2018-3A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VoyaCloLtdSeries20183AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Voya CLO Ltd, Series 2018-3A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VoyaCloLtdSeries20183AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Voya CLO Ltd, Series 2018-3A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Rule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Rule 10b5 1 Arr Modified [Flag]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Rule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Rule 10b5 1 arrangement modified.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Rule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Rule 10b5-1 Arrangement Modified</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NortheastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Northeast.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NortheastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Northeast [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NortheastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States - Northeast</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DiscoParentIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disco Parent Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DiscoParentIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Disco parent Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DiscoParentIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Disco Parent, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Organization and Basis of Presentation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value measurement with unobservable inputs reconciliation recurring basis asset paid-in-kind interest.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Paid In Kind Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Paid-in-kind interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Address, Postal Zip Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Postal Zip Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BusinessServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Business services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BusinessServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BusinessServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Business Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 9/2029</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Nine [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan Due September Two Thousand Twenty Nine.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Operating Activity, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Cash Provided by (Used in) Operating Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AutomotiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Automotive</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AutomotiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Automotive [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AutomotiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Automotive.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 9/2022</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due september two thousand twenty two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ForestProductsAndPaperSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Forest Products and Paper Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ForestProductsAndPaperSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Forest products and paper sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ForestProductsAndPaperSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Forest Products &amp; Paper</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UsaDebuskLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">USA Debusk LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UsaDebuskLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">USA Debusk LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UsaDebuskLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">USA Debusk LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FolletCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Follet Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FolletCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Follet Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FolletCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Follet corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PayleaseLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PayLease, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PayleaseLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">PayLease, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PayleaseLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Paylease, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty Eight Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty twenty eight notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2028 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarisLifeSciencesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Caris Life Sciences, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarisLifeSciencesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Caris Life Sciences Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarisLifeSciencesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Caris Life Sciences Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueJanuaryTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Revolving Loan Due 1/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueJanuaryTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan Due January Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueJanuaryTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien revolving loan due January two thousand twenty four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ParkAvenueInstitutionalAdvisersCloLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Park Avenue Institutional Advisers CLO Ltd, Series 2018-1A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ParkAvenueInstitutionalAdvisersCloLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Park Avenue Institutional Advisers Clo Ltd, Series Two Thousand Eighteen One A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ParkAvenueInstitutionalAdvisersCloLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Park avenue institutional advisers clo ltd, series two thousand eighteen one A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividend Income, Operating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Dividend Income, Operating, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Dividend Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Accretion of original issue discount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amortization of Debt Discount (Premium)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization of discount on debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Available For Sale Securities [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SMATechnologiesHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">S M A Technologies Holdings L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SMATechnologiesHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">S M A Technologies Holdings L L C.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SMATechnologiesHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SMA Technologies Holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TangoManagementConsultingTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tango Management Consulting Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TangoManagementConsultingTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tango Management Consulting Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TangoManagementConsultingTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tango Management Consulting, LLC #2</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 5/2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due May Two Thousand Twenty Seven.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due May Two Thousand Twenty Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TruckLiteCoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Truck-Lite Co.,LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TruckLiteCoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Truck-Lite Co.,LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TruckLiteCoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Truck-Lite Co., LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SixthStreetLendingPartnersMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sixth Street Lending Partners [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SixthStreetLendingPartnersMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sixth Street Lending Partners.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SixthStreetLendingPartnersMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sixth Street Lending Partners</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InsuranceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Insurance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InsuranceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Insurance [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InsuranceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Insurance.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Address, Address Line One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in accounting principle, accounting standards update, immaterial effect [true false]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transfers into (out of) Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Transfers into (out of) Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends Payable [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Hierarchy and NAV</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings per common share-basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q2SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2025 Q2 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q2SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2025 Q2 supplemental dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q2SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2025 Q2 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Cash Flow Information [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental Information:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Foreign Currency Transactions and Translations Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Foreign Currency</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value measurement with unobservable inputs reconciliation recurring basis asset net amortization of discount on securities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Net Amortization Of Discount On Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net amortization of discount on securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EventusBuyerLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Eventus Buyer, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EventusBuyerLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Eventus Buyer, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EventusBuyerLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Eventus Buyer, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InformationClearinghouseLLCAndMSMarketServiceLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Information Clearinghouse, LLC and MS Market Service,LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InformationClearinghouseLLCAndMSMarketServiceLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Information Clearinghouse L L C And M S Market Service L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InformationClearinghouseLLCAndMSMarketServiceLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Information Clearing house LLC And MS Market Service LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Component of Carrying Value of Convertible Notes and Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of component of carrying value of convertible notes and interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Component Of Carrying Value Of Convertible Notes and Interest Rate [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 4/2036</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due April Two Thousand Thirty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due april two thousand thirty six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeeExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Management fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Management Fee Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Management fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 8/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien loan Due August Two Thousand Twenty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due August Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SapphireSoftwareBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sapphire Software Buyer Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SapphireSoftwareBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sapphire software buyer inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SapphireSoftwareBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sapphire Software Buyer, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, Interest Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments in and advances to affiliates, interest income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputComparabilityAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input, Comparability Adjustment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputComparabilityAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Comparable Multiple</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">First-lien loan ($55,820 par, due 1/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 1/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due January Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due january two thousand twenty five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassBUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Class B units.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassBUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class B Units [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassBUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class B Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentIncomeOther_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment income other.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentIncomeOther_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income Other</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentIncomeOther_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Other Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TSImagineIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">TS Imagine Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TSImagineIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">TS Imagine Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TSImagineIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">TS Imagine Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditPartnersJVLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Credit Partners JV, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditPartnersJVLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured Credit Partners JV, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditPartnersJVLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Credit Partners JV, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Five One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan (GBP 3,766 par, Due 12/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Five One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MinorityInterestOwnershipPercentageByParent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsidiary, Ownership Percentage, Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MinorityInterestOwnershipPercentageByParent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Noncontrolling Interest, Ownership Percentage by Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of hurdle rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Pre Incentive Fee Net Investment Income Hurdle Rate Quarterly</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of pre incentive fee net investment income hurdle rate quarterly.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeInvestmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Investment Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeInvestmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments, Debt and Equity Securities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net realized losses on foreign currency transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Gain (Loss), Foreign Currency Transaction, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Foreign currency transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Transfers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNotesDueJuneTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Convertible Note (AUD 3,000 Par, Due 6/2027)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNotesDueJuneTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Convertible Notes Due June Two Thousand Twenty Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNotesDueJuneTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Convertible Notes Due June Two Thousand Twenty Seven.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonSharesClassAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Shares Class A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonSharesClassAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Shares Class A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonSharesClassAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common Shares Class A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AlphaMidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Alpha Midco, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AlphaMidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Alpha Midco Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AlphaMidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Alpha Midco Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IntelePeerHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">IntelePeer Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IntelePeerHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Intele Peer Holdings Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IntelePeerHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">IntelePeer Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HotelGamingAndLeisureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hotel, Gaming and Leisure.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HotelGamingAndLeisureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hotel Gaming And Leisure [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HotelGamingAndLeisureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hotel, Gaming and Leisure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Valuation Approach and Technique</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Approach and Technique [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">First-lien revolving loan ($1,320 par, due 1/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 1/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due January Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due January Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGlobalMarketStrategiesCLOLtdSeriesTwoThousandSeventeenFourAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carlyle global market strategies CLO Ltd series two thousand seventeen four A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGlobalMarketStrategiesCLOLtdSeriesTwoThousandSeventeenFourAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Carlyle Global Market Strategies C L O Ltd Series Two Thousand Seventeen Four A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGlobalMarketStrategiesCLOLtdSeriesTwoThousandSeventeenFourAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Carlyle Global Market Strategies CLO Ltd, Series 2017-4A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of commitments to fund investments in current portfolio companies.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Commitments To Fund Investments In Current Portfolio Companies [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Commitments To Fund Investments In Current Portfolio Companies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Income, Operating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Income, Operating, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 8/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due August Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due August Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_USRParentIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">USR Parent, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_USRParentIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">U S R Parent Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_USRParentIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">USR Parent, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MitnickCorporatePurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Mitnick Corporate Purchaser, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MitnickCorporatePurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Mitnick Corporate Purchaser, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MitnickCorporatePurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Mitnick corporate purchaser, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of excess pre-incentive fee net investment income, quarterly after catch-up achieved.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Pre Incentive Fee Net Investment Income Quarterly After Catch Up Achieved</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of excess pre-Incentive Fee net investment income quarterly</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net realized (gains) losses on foreign currency transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Realized (Gains) Losses on Foreign Currency Transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net realized (gains) losses on foreign currency transactions.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($29,639 par, due 5/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due May Two Thousand Twenty Four Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due may two thousand twenty four four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Par or Stated Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common shares, par value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Number of common stock par share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfAdoptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Standards Update [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SprinklrIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sprinklr, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SprinklrIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sprinklr Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SprinklrIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sprinklr, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan (EUR 3,150 par, due 11/2029)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due November Two Thousand Twenty Nine Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan Due November Two Thousand Twenty Nine.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GreenshootBidcoBVMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Greenshoot Bidco B V [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GreenshootBidcoBVMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Greenshoot Bidco B. V.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GreenshootBidcoBVMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Greenshoot Bidco B.V</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BaseRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Base Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BaseRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Base Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Repayments of Short-Term Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Repayments of Short-Term Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Repayments on debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArrowheadPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Arrowhead Pharmaceuticals Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArrowheadPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Arrowhead pharmaceuticals inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArrowheadPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Arrowhead Pharmaceuticals, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Related Commitment Fees and Debt Issuance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitment fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeeExpenseIncomeBased_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fee Expense, Income-Based</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeeExpenseIncomeBased_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BlueSnapIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BlueSnap, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BlueSnapIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Blue Snap Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BlueSnapIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BlueSnap, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Other Operating Liabilities, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Other Operating Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Securities, Available-for-Sale, Amortized Cost, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReliaQuestLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Relia Quest LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReliaQuestLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ReliaQuest, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReliaQuestLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Relia Quest L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanMayTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien revolving loan ($2,400 par, due 5/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanMayTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan May Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanMayTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien revolving loan may two thousand twenty four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Securities, Available-for-Sale, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanDueAugustTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL FILO Term Loan due 8/2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanDueAugustTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ABL FILO Term Loan Due August Two Thousand Twenty Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanDueAugustTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">A B L F I L O Term Loan Due August Two Thousand Twenty Seven.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueMayTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Convertible Note due 5/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueMayTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Convertible Note Due May Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueMayTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Convertible Note Due May Two Thousand Twenty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="currency_EUR_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Euro Member Countries, Euro</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="currency_EUR_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">EUR</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Expense, after Reduction of Fee Waiver and Reimbursement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienLoanDueJuneTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Second-lien loan due 6/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienLoanDueJuneTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Second Lien Loan Due June Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienLoanDueJuneTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Second Lien Loan Due June Two Thousand Twenty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net realized (gains) losses on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized gains (losses) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Undistributed net realized gains (losses) - tax basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Realized Investment Gains (Losses), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Realized Gain/(Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperatingPaidInCash_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Income, Operating, Paid in Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperatingPaidInCash_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest from investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TangoManagementConsultingLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tango Management Consulting, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TangoManagementConsultingLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tango Management Consulting L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TangoManagementConsultingLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tango Management Consulting, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments for Hedge, Investing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 4/2031</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due April two thousand thirty one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due April Two Thousand Thirty One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_DE_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Germany</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_DE_lbl" xlink:role="http://www.xbrl.org/2003/role/label">GERMANY</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">First-lien loan ($56,963 par, due 7/2028)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan Due 7/2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-Lien Loan due July Two Thousand Twenty Eight [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-Lien Loan due July Two Thousand Twenty Eight.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">First-lien loan ($40,353 par, due 3/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($40,455 par, due 3/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien loan Due March Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due March Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwaps_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swaps.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwaps_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swaps</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwaps_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Interest rate swaps</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($69,475 par, due 5/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due May Two Thousand Twenty Four Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due may two thousand twenty four five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchases or originations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CapitalEquipmentSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Capital Equipment Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CapitalEquipmentSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Capital equipment sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CapitalEquipmentSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Capital Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDerivativeInstrumentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Derivative Instruments [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDerivativeInstrumentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Amounts Paid and Received on Interest Rate Swap Transactions, Excluding Upfront Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross Additions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, at Fair Value, Gross Additions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BenefitStreetPartnersCloLtdSeriesTwoThousandFifteenEightAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Benefit Street Partners CLO Ltd, Series 2015-8A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BenefitStreetPartnersCloLtdSeriesTwoThousandFifteenEightAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Benefit Street Partners Clo Ltd Series Two Thousand Fifteen Eight A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BenefitStreetPartnersCloLtdSeriesTwoThousandFifteenEightAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Benefit Street Partners Clo Ltd, Series 2015-8A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeNotionalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Notional Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeNotionalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Notional amount of interest rate swap</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeNotionalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Notional value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023 Q3 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023 Q3 supplemental dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023 Q3 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_OwnershipDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ownership [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeriesFPreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Series F Preferred Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeriesFPreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Series F Preferred Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Current Fiscal Year End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current Fiscal Year End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Long-Term Debt Instruments [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_QSRAcquisitionCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">QSR Acquisition Co.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_QSRAcquisitionCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">QSR Acquisition Co. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_QSRAcquisitionCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">QSR Acquisition Co.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CirrusBidcoLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cirrus Bidco Ltd [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CirrusBidcoLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cirrus Bidco ltd .</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CirrusBidcoLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cirrus (Bidco) Ltd</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScorpioBidcoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Scorpio Bidco</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScorpioBidcoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scorpio Bidco [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScorpioBidcoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Scorpio Bidco.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentQuarterlyReport_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Document Quarterly Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyTwoThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan Due 12/2022</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyTwoThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-Lien Loan Due December Two Thousand Twenty-Two Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyTwoThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-Lien Loan Due 12/2022.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCostAndExpenseOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Cost and Expense, Operating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCostAndExpenseOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueAugustTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien revolving loan due 8/2023</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueAugustTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan Due August Two Thousand Twenty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueAugustTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Revolving Loan Due August Two Thousand Twenty Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJuneTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 6/2031</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJuneTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due June Two Thousand Thirty One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJuneTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due June Two Thousand Thirty One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassAUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Class A units.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassAUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class A Units [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassAUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class A Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByBalanceSheetGroupingTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, by Balance Sheet Grouping [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Address, State or Province</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, State or Province</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($47,122 par, Due 5/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due May Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due May Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossRatio_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Investment Income (Loss) Ratio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossRatio_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ratio of net investment income to average net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Amount Available</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Remaining Borrowing Capacity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, remaining borrowing capacity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_EquityMethodInvesteeNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 12/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedBalanceShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedBalanceShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Balance, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandTwentyEightOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Revolving Loan ($0 par, due 10/2028)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandTwentyEightOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan Due October Two Thousand Twenty Eight One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandTwentyEightOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien revolving loan due October two thousand twenty eight one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 9/2023</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due September Two Thousand Twenty Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Preferred Stock, Shares Outstanding, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Preferred Stock, Shares Outstanding, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MidoceanCreditCloLtdSeries20189AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">MidOcean Credit CLO Ltd, Series 2018-9A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MidoceanCreditCloLtdSeries20189AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">MidOcean Credit CLO Ltd, Series 2018-9A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SouthMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">South.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SouthMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">South [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SouthMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States - South</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementGeographicalAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Geographical [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementGeographicalAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Geographical</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeverinAcquisitionLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Severin Acquisition, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeverinAcquisitionLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Severin Acquisition, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeverinAcquisitionLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Severin Acquisition, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Accrued Interest Receivable, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Interest receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentySixTwentyEightTwentyNineAndTwentyThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Six, Twenty Eight, Twenty Nine and Twenty Thirty Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentySixTwentyEightTwentyNineAndTwentyThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two Thousand Twenty Six, Twenty Eight, Twenty Nine and Twenty Thirty Notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentySixTwentyEightTwentyNineAndTwentyThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2026 Notes, 2028 Notes, 2029 Notes and 2030 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MeritSoftwareFinanceHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Merit Software Finance Holdings, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MeritSoftwareFinanceHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Merit Software Finance Holdings, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MeritSoftwareFinanceHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Merit Software Finance Holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of non-qualifying assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Non Qualifying Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of non-qualifying assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other General and Administrative Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other general and administrative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfessionalFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Professional Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfessionalFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Professional fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value of securities as percentage of net assets in percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Of Securities As Percentage Of Net Assets In Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value of securities as percentage of net assets in percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($32,242 par, Due 12/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Six Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Six Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AerospaceAndDefenseSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aerospace and Defense Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AerospaceAndDefenseSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aerospace and defense sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AerospaceAndDefenseSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aerospace &amp; Defense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_JointVentureFormationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Financial Highlights of Joint Venture</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_JointVentureFormationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Joint Venture Formation [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($17,781 par, due 1/2021)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-Lien Loan Due January Two Thousand Twenty One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-Lien Loan Due January 2021.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">2024 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty four notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Four Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RetailAndConsumerProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retail And Consumer Products [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RetailAndConsumerProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Retail and Consumer Products.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RetailAndConsumerProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Retail and Consumer Products</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 12/2022</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CifcCloLimitedSeriesTwoThousandAndTwentyOneFourAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">CIFC CLO Ltd, Series 2021-4A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CifcCloLimitedSeriesTwoThousandAndTwentyOneFourAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">CIFC CLO Limited Series Two Thousand and Twenty One Four A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CifcCloLimitedSeriesTwoThousandAndTwentyOneFourAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">CIFC CLO Limited series two thousand and twenty one four A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OctagonInvestmentPartnersEighteenLimitedSeriesTwoThousandEighteenEighteenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Octagon Investment Partners Eighteen Limited, Series Two Thousand Eighteen Eighteen A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OctagonInvestmentPartnersEighteenLimitedSeriesTwoThousandEighteenEighteenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Octagon investment partners eighteen limited, series two thousand eighteen eighteen A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HomecareSoftwareSolutionsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Homecare Software Solutions, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HomecareSoftwareSolutionsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Homecare Software Solutions L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HomecareSoftwareSolutionsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Homecare Software Solutions, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityInvestmentVariableInterestRateTypeExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Investment, Variable Interest Rate, Type [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityInvestmentVariableInterestRateTypeExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity Investment, Variable Interest Rate, Type [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInIncentiveFeePayableIncomeBased_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Incentive Fee Payable, Income-Based</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInIncentiveFeePayableIncomeBased_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net investment income payable to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInIncentiveFeePayableIncomeBased_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Incentive fees on net investment income payable to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RRLtdSeriesTwoThousandTwentyEightAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">RR Ltd, Series 2020-8A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RRLtdSeriesTwoThousandTwentyEightAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">R R Ltd, Series Two Thousand Twenty Eight A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RRLtdSeriesTwoThousandTwentyEightAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">R R ltd, series two thousand twenty eight A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Method Investment, Nonconsolidated Investee [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ServiceChannelHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ServiceChannel Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ServiceChannelHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Service Channel Holdings, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ServiceChannelHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ServiceChannel Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TRPAssetsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">TRP Assets, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TRPAssetsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">T R P Assets L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TRPAssetsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">TRP Assets, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive fees on net capital gains.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fees On Net Capital Gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net capital gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MediaDiversifiedAndProductionSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Media Diversified and Production Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MediaDiversifiedAndProductionSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Media diversified and production sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MediaDiversifiedAndProductionSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Media: Diversified &amp; Production</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($44,806 par, due 11/2028)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due November Two Thousand Twenty Eight [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan Due November Two Thousand Twenty Eight.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense, Operating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Expense, Operating, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Interest expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred financing costs and original issue discounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement Inputs and Valuation Techniques [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 8/2022</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due August Two Thousand Twenty Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due August Two Thousand Twenty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($19,750 par, due 10/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Five Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due october two thousand twenty five four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentInterestRatePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate, PIK</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentInterestRatePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Interest Rate, Paid in Kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value of securities as percentage of net assets amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Of Securities As Percentage Of Net Assets Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value of securities as percentage of net assets amount.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q4BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023 Q4 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q4BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023 Q4 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of management fee in excess of annual rate on gross assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Management Fee In Excess Of Annual Rate On Gross Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of management fee in excess of annual rate on gross assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense, Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Interest Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwentyTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan Due 7/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwentyTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-Lien Loan due July Twenty Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwentyTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-Lien Loan due July Twenty Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BabylonFincoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Babylon Finco Limited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BabylonFincoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Babylon Finco Limited [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BabylonFincoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Babylon finco limited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLiabilityNotionalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Liability, Notional Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLiabilityNotionalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Notional Amount Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLiabilityNotionalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Notional value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 9/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien loan Due September Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JointVentureInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Joint Venture Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JointVentureInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Joint venture investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JointVentureInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Joint venture investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Transaction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PikesPeakCloSeriesTwoThousandTwentyOneNineAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pikes Peak CLO, Series 2021-9A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PikesPeakCloSeriesTwoThousandTwentyOneNineAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pikes Peak Clo, Series Two Thousand Twenty One Nine A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PikesPeakCloSeriesTwoThousandTwentyOneNineAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pikes peak clo, series two thousand twenty one nine A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($23,798 par, Due 10/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due October Two Thousand Twenty Five Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Five Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty two convertible notes member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Two Convertible Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022 Convertible Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Incentive fees accrued related to expense (reversal) of capital gains fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees accrued related to expense (reversal) of capital gains fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fees Accrued Related To Expense (Reversal) Capital Gains Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive fees accrued related to expense (reversal) capital gains fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WholesaleSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Wholesale Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WholesaleSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Wholesale sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WholesaleSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Wholesale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VitaTopcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vita Topco, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VitaTopcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Vita Topco, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VitaTopcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Vita Topco, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Treasury stock, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Common, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Treasury stock, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Treasury stock, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIssuerNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Issuer Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 7/2033</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due July Two Thousand Thirty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due July two thousand thirty three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OutsystemsLuxcoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">OutSystems Luxco SARL</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OutsystemsLuxcoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Outsystems Luxco [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OutsystemsLuxcoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Outsystems Luxco.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Rate Derivatives, at Fair Value, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Derivatives, at Fair Value, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Market Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Fair market value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleCreditSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Carlyle Credit Solutions, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleCreditSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carlyle Credit Solutions, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleCreditSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Carlyle Credit Solutions, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured Product Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingStandardsUpdate202404Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Standards Update 2024-04 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingStandardsUpdate202404Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ASU 2024-04</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Value, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, $0.01 par value; 100,000,000 shares authorized; no shares issued and outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q3 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 Q3 supplemental dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q3 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expenses incurred</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Selling, General and Administrative Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Selling, General and Administrative Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Maturity Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, maturity date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Credit [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured credit.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InternetServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Internet Services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InternetServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Internet Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InternetServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Internet Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instrument [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealEstateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Real Estate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealEstateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Real Estate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Gross Reductions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, at Fair Value, Gross Reductions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BattalionCloLtdSeriesTwoThousandTwentyOneTwentyOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Battalion CLO Ltd, Series 2021-21A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BattalionCloLtdSeriesTwoThousandTwentyOneTwentyOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Battalion CLO Ltd Series Two Thousand Twenty One Twenty One A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BattalionCloLtdSeriesTwoThousandTwentyOneTwentyOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Battalion CLO Ltd Series 2021-21A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Incentive Fee to Average Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Portfolio turnover</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoansDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($46,364 par, due 12/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoansDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loans Due December Two Thousand Twenty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoansDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loans Due December Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonClassBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class B Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonClassBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Class B [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 3 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net realized and unrealized gains (losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Gain (Loss) on Investment, Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Six</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Measurements of Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Unrealized gains (losses) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain (Loss) on Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net Change In Unrealized Gain/(Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net realized (gains) losses on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Net change in unrealized (gains) losses on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($17,314 par, Due 1/2028)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due January Two Thousand Twenty Eight.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due January Two Thousand Twenty Eight [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured credit investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Credit Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured credit investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CrownPointCloLtdSeriesTwoThousandTwentyOneTenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Crown Point CLO Ltd, Series 2021-10A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CrownPointCloLtdSeriesTwoThousandTwentyOneTenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Crown Point CLO Ltd, Series Two Thousand Twenty One Ten A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CrownPointCloLtdSeriesTwoThousandTwentyOneTenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Crown Point CLO Ltd, series two thousand twenty one ten A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($17,018 par,Due 4/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due April Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril232027Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility Maturity on April 23, 2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril232027Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility Maturity on April 23, 2027 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril232027Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving credit facility maturity on April 23, 2027.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance,Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares Outstanding, End of Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Shares out standing</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IRGSEHoldingCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">IRGSE Holding Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IRGSEHoldingCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">I R G S E Holding Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IRGSEHoldingCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">IRGSE Holding Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Other Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FullsteamOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fullsteam Operations LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FullsteamOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fullsteam Operations LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FullsteamOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fullsteam Operations, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienLoanDueOctoberTwoThousandTwentyNineOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Second lien loan due October two thousand twenty nine one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienLoanDueOctoberTwoThousandTwentyNineOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Second Lien Loan Due October Two Thousand Twenty Nine One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienLoanDueOctoberTwoThousandTwentyNineOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Second-lien loan($43,490par,due10/2029)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesDividendIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesDividendIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, Dividend Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesDividendIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments in and advances to affiliates, dividend income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and contingencies (Note 8)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LiabilitiesAndMembersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liabilities and Members' Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LiabilitiesAndMembersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities And Members' Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LiabilitiesAndMembersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liabilities and members' equity.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MagnetiteCloLtdSeriesTwoThousandTwentyOneThirtyAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Magnetite CLO Ltd, Series Two Thousand Twenty One Thirty A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MagnetiteCloLtdSeriesTwoThousandTwentyOneThirtyAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Magnetite CLO Ltd, series two thousand twenty one thirty A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyMarketValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Per share market value at end of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyMarketValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Market Value, Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other General and Administrative Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">General and Administrative Expense [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BswiftLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Bswift LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BswiftLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Bswift LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BswiftLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Bswift LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan due 7/2023</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-lien loan due July Two Thousand Twenty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien loan due 7/2023.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument, basis spread on variable rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Basis Spread on Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Percentage of loans at floating interest rates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MotusLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Motus, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MotusLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Motus, L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MotusLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Motus, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends Payable [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioForecastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Forecast [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioForecastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Forecast</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Products</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Products [member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured products.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxBenefitPertainingToNetUnrealizedLossRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Benefit Pertaining To Net Unrealized Loss Related To Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxBenefitPertainingToNetUnrealizedLossRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred tax benefit pertaining to net unrealized loss related to investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxBenefitPertainingToNetUnrealizedLossRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax benefit pertaining to net unrealized losses related to investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 7/2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due July Two Thousand Twenty Seven.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due July Two Thousand Twenty Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BainCapitalCreditCLOLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Bain Capital Credit CLO Ltd, Series 2018-1A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BainCapitalCreditCLOLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Bain Capital Credit CLO Ltd Series Two Thousand Eighteen One A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BainCapitalCreditCLOLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Bain Capital Credit C L O Ltd Series Two Thousand Eighteen One A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">2023 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty three notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Three Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ContainerPackagingAndGlassSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Container, Packaging and Glass Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ContainerPackagingAndGlassSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Container, packaging and glass sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ContainerPackagingAndGlassSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Containers, Packaging &amp; Glass</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain (Loss), Investment and Derivative, Operating, Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income tax provision</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Income tax provision</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetwrixCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Netwrix Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetwrixCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Netwrix Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetwrixCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Netwrix Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_AU_lbl" xlink:role="http://www.xbrl.org/2003/role/label">AUSTRALIA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_AU_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Australia</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienNoteOneDueJuneTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien note due 6/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienNoteOneDueJuneTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Note One Due June Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienNoteOneDueJuneTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Note One Due June Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Net Assets Resulting from Operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase (decrease) in net assets resulting from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Increase (Decrease) in Net Assets Resulting from Operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase in net assets resulting from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Manufacturing</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Manufacturing [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Manufacturing.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of excess pre-incentive fee net investment income for immediate preceding calendar quarter.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Excess Pre Incentive Fee Net Investment Income For Immediate Preceding Calendar Quarter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of excess pre-incentive fee net investment income for immediate preceding calendar quarter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdviserMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Adviser.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdviserMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adviser [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdviserMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adviser</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueSeptemberTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Convertible Note Due September Two Thousand Twenty Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueSeptemberTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Convertible Note Due September Two Thousand Twenty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueSeptemberTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Convertible Note ($2,602 par, Due 9/2023)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 11/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due November Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due november two thousand twenty five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanJulyTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Revolving Loan due 7/2022</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanJulyTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan July Two Thousand Twenty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanJulyTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien revolving loan July two thousand twenty two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Term Debt, Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingencies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loss Contingencies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Investments, at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value of securities as percentage of net assets amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Denominator for basic weighted average shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Denominator for basic weighted average shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Weighted Average Number of Shares Outstanding, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average shares of common stock outstanding&#8212;basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArtisanBidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Artisan Bidco, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArtisanBidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Artisan Bidco, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArtisanBidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Artisan Bidco, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementScenarioAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scenario [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementScenarioAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Scenario</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClinicientIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Clinicient, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClinicientIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Clinicient, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClinicientIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Clinicient Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL FILO Term Loan due 12/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ABL FILO Term Loan Due December Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ABL FILO term loan due december two thousand twenty five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AledadeIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aledade, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AledadeIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aledade, inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AledadeIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aledade, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentySevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due may two thousand twenty seven one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentySevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due May Two Thousand Twenty Seven One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentySevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan($1,542par,due5/2027)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($30,261 par, Due 6/2023)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due June Two Thousand Twenty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan Due June Two Thousand Twenty Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetPledgedAsCollateralMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Pledged as Collateral [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetPledgedAsCollateralMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset Pledged as Collateral</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsFairValueDisclosureNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments Fair Value Disclosure Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsFairValueDisclosureNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsFairValueDisclosureNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsFairValueDisclosureNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments fair value disclosure net.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Events</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 Notes, 2026 Notes, 2028 Notes and 2029 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Four Twenty Six Twenty Eight And Twenty Nine [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">2024 Notes, 2026 Notes, 2028 Notes and 2029 Notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Carrying Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Carrying value of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Outstanding debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt (net of deferred financing costs of $22,693 and $24,411, respectively)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Agreements and Related Party Transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Cash_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Cash_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q2SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023 Q2 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q2SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023 Q2 supplemental dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q2SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023 Q2 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromUnsecuredNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Unsecured Notes Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromUnsecuredNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from issuance of debt, net of underwriting discount, offering costs and original issue discount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StockOfferingValueSharesAuthorizedToBeSold_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Offering Value Shares Authorized To Be Sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StockOfferingValueSharesAuthorizedToBeSold_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Stock offering value shares authorized to be sold.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StockOfferingValueSharesAuthorizedToBeSold_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock offering value shares authorized to be sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Variable Rate [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesAPreferredStockWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Series A Preferred Stock Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesAPreferredStockWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Series A Preferred Stock Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesAPreferredStockWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Series A preferred stock warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 4/2034</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due April Two Thousand Thirty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due April Two Thousand Thirty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders' equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Par or Stated Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, par value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfIndustryCompositionOfJointVentureInvestmentsPortfolioAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Industry Composition of SCP's Portfolio at Fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfIndustryCompositionOfJointVentureInvestmentsPortfolioAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary of Industry Composition of Joint Venture Investments Portfolio at Fair Value [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfIndustryCompositionOfJointVentureInvestmentsPortfolioAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of industry composition of joint venture investments portfolio at fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BigWombatHoldingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Big Wombat Holding Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BigWombatHoldingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Big Wombat Holding Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BigWombatHoldingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Big Wombat Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RaptorUsBuyerIiCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Raptor US Buyer II Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RaptorUsBuyerIiCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Raptor us buyer II corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RaptorUsBuyerIiCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Raptor US Buyer II Corp</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ApellisPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Apellis Pharmaceuticals, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ApellisPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Apellis Pharmaceuticals, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ApellisPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Apellis Pharmaceuticals, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Basis of Accounting, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis of Presentation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien revolving loan April two thousand twenty five two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan April Two Thousand Twenty Five Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien revolving loan ($1,411 par, due 4/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UtilitiesElectricSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Utilities Electric Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UtilitiesElectricSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Utilities electric sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UtilitiesElectricSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Utilities: Electric</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BCTOAcePurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BCTO Ace Purchaser, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BCTOAcePurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">B C T O Ace Purchaser Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BCTOAcePurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">B C T O Ace Purchaser Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BCTOAcePurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">BCTO Ace Purchaser, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Stockholders' Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeriesCPreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Series C Preferred Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeriesCPreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Series C Preferred Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SubordinatedNoteMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Subordinated note.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SubordinatedNoteMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subordinated Note [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SubordinatedNoteMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subordinated Note</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 7/2035</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due July Two Thousand Thirty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due July Two Thousand Thirty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($333 par, due 5/2029)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due May Two Thousand Twenty Nine [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien Loan due may two thousand twenty nine.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Approach and Technique [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Valuation Approach and Technique</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClearCompanyLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ClearCompany, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClearCompanyLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Clear Company L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClearCompanyLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Clear Company L L C</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeriesAPreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Series A Preferred Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeriesAPreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Series A Preferred Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanParDueSeptemberTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Revolving Loan due 9/2021</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanParDueSeptemberTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-lien revolving loan par, due September Two thousand twenty-one [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanParDueSeptemberTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien revolving loan par, due September Two thousand twenty-one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Use of Estimates, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Use of Estimates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JonasCollectionsAndRecoveryIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Jonas Collections and Recovery, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JonasCollectionsAndRecoveryIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Jonas Collections And Recovery Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JonasCollectionsAndRecoveryIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Jonas Collections and Recovery, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CurrentMarketPricePerSharePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of current market price per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CurrentMarketPricePerSharePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Current Market Price Per Share Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CurrentMarketPricePerSharePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Current market price per share percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OilGasAndConsumableFuelsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Oil, Gas and Consumable Fuels.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OilGasAndConsumableFuelsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Oil Gas And Consumable Fuels [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OilGasAndConsumableFuelsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Oil, Gas and Consumable Fuels</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan (AUD 40,000 par, Due 12/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Six One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Six One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Treasury Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Common [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfLoansAtFloatingInterestRates_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of loans at floating interest rates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfLoansAtFloatingInterestRates_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Loans at Floating Interest Rates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfLoansAtFloatingInterestRates_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of loans at floating interest rates.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OverAllotmentOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Over-Allotment Option [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OverAllotmentOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Overallotment Option</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Address, Address Line Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value of Financial Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Date Declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Date Declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends date declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MDAmericaEnergyLimitedLiabilityCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">MD America Energy Limited Liability Company.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MDAmericaEnergyLimitedLiabilityCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">M D America Energy Limited Liability Company [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MDAmericaEnergyLimitedLiabilityCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">MD America Energy LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PdiTaHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">PDI TA Holdings, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PdiTaHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PDI TA Holdings, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PdiTaHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PDI TA Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SignificantAccountingPoliciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Significant Accounting Policies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SignificantAccountingPoliciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Significant accounting policies.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_NL_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Netherlands</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_NL_lbl" xlink:role="http://www.xbrl.org/2003/role/label">NETHERLANDS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NinetyNineCentsOnlyStoresLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">99 Cents Only Stores LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NinetyNineCentsOnlyStoresLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ninety Nine Cents Only Stores L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NinetyNineCentsOnlyStoresLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">99 Cents Only Stores LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Fair Value, Ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Fair Value, Beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments at fair value (amortized cost of $1,033,006)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total investments at fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_US_lbl" xlink:role="http://www.xbrl.org/2003/role/label">UNITED STATES</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_US_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 12/2023</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DaySmartHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">DaySmart Holdings, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DaySmartHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Day Smart Holdings L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DaySmartHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">DaySmart Holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksRelatedToOurPortfolioCompanyInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Risks Related to Our Portfolio Company Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksRelatedToOurPortfolioCompanyInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Risks Related to Our Portfolio Company Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 10/2022</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan One Due October Two Thousand Twenty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan One Due October Two Thousand Twenty Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument, Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MoranFoodsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Moran Foods, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MoranFoodsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Moran Foods L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MoranFoodsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Moran Foods, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputDiscountRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input, Discount Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputDiscountRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Discount Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Capital gains accrue following March 31, 2014.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Capital Gains Accrue Following March Thirty First Two Thousand Fourteen [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Capital Gains Accrue Following March 31, 2014</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MezzanineDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Mezzanine debt investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MezzanineDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Mezzanine Debt Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MezzanineDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Mezzanine Debt Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesAndOtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Liabilities and Other Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesAndOtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesAndOtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Accrued expenses and other liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Expense and Other Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid expenses and other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanParDueSeptemberTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 9/2021</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanParDueSeptemberTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-lien loan par, due September Two thousand twenty-one [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanParDueSeptemberTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien loan par, due September Two thousand twenty-one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Instruments and Hedging Activities Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanOctoberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Revolving Loan due 10/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanOctoberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan October Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanOctoberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien revolving loan October two thousand twenty four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VarinemGermanBidcoGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Varinem German Bidco GmbH [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VarinemGermanBidcoGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Varinem german bidco gmbH .</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VarinemGermanBidcoGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Varinem German Bidco GmbH</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PenneyBorrowerLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Penney Borrower, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PenneyBorrowerLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Penney Borrower LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PenneyBorrowerLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Penney Borrower, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueTransfers_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transfers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueTransfers_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, at Fair Value Transfers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueTransfers_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments in and advances to affiliates, at fair value transfers.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HighTechIndustriesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">High Tech Industries Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HighTechIndustriesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">High tech industries sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HighTechIndustriesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">High Tech Industries</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxExpensePertainingToNetRealizedGainsRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Expense Pertaining to Net Realized Gains Related to Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxExpensePertainingToNetRealizedGainsRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tax expense pertaining to net realized gains related to investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxExpensePertainingToNetRealizedGainsRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax expense pertaining to net realized gains related to investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnMarch42025Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility Maturity On March 4, 2025 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnMarch42025Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving credit facility maturity on march 4, 2025.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnMarch42025Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility Maturity On March 4, 2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArcwoodEnvironmentalIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Arcwood Environmental Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArcwoodEnvironmentalIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Arcwood Environmental Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArcwoodEnvironmentalIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Arcwood Environmental, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrganizationAndBasisOfPresentationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization and Basis of Presentation [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrganizationAndBasisOfPresentationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Organization and Basis of Presentation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan due 12/2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Eight [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan Due December Two Thousand Twenty Eight.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChemicalsSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Chemicals Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChemicalsSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Chemicals</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StockIssuedDuringPeriodValueOfRemained_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Value of Remained</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StockIssuedDuringPeriodValueOfRemained_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Stock issued during period value of remained.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StockIssuedDuringPeriodValueOfRemained_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock issued during period value of remained</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan Due June Two Thousand Twenty Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due June Two Thousand Twenty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($30,261 par, Due 6/2022)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit Facility [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Method Investment, Ownership Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of investments ownership</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Equity ownership percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfInvestmentsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Investments [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of excess catch-up provision for pre-incentive fee net investment income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Excess Catch Up Provision For Pre Incentive Fee Net Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of excess catch-up provision for pre-Incentive Fee net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Debt Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwentyTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 3/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwentyTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-lien Loan Due March Twenty Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwentyTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due March Twenty Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TIBCOSoftwareIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">TIBCO Software Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TIBCOSoftwareIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">T I B C O Software Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TIBCOSoftwareIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">TIBCO Software Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HMPOmnimediaLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">HMP Omnimedia LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HMPOmnimediaLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hmp omnimedia llc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HMPOmnimediaLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">HMP Omnimedia, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsOwnedEstimatedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments owned estimated cost basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsOwnedEstimatedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments Owned Estimated Cost Basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsOwnedEstimatedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments owned estimated cost basis.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Treasury stock at cost; 664,250 and 664,250 shares held, respectively</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Treasury Stock, Value, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reinvestment of dividends during the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LegPurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leg Purchaser Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LegPurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Leg purchaser inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LegPurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leg Purchaser Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwothousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($31,580 par, due 5/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwothousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due May TwoThousand Twenty Six One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwothousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due may two thousand twenty six one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related and Nonrelated Parties [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityAverageOutstandingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Average Outstanding Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityAverageOutstandingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Average debt outstanding (in millions)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AresLoanFundingILtdSeriesTwoThousandTwentyOneAlfaClassEMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ares Loan Funding I Ltd Series Two Thousand Twenty One ALFA Class E [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AresLoanFundingILtdSeriesTwoThousandTwentyOneAlfaClassEMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ares Loan Funding I Ltd, Series 2021-ALFA, Class E</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AresLoanFundingILtdSeriesTwoThousandTwentyOneAlfaClassEMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ares Loan Funding I Ltd Series Two Thousand Twenty One ALFA Class E.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienLoanDueOctoberTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Second-lien Loan due 10/2029</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienLoanDueOctoberTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Second-lien Loan Due October Two Thousand Twenty Nine.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienLoanDueOctoberTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Second Lien Loan Due October Two Thousand Twenty Nine [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($27,000 par, due 12/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due December two thousand twenty six four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Six Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Address, City or Town</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, City or Town</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum percentage of voting securities in investment portfolio.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum Percentage Of Voting Securities In Investment Portfolio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum percentage of voting securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q2BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023 Q2 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q2BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023 Q2 base dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q2BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023 Q2 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty twenty three notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty Three Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UtilitiesOilAndGasSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Utilities Oil and Gas Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UtilitiesOilAndGasSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Utilities oil and gas sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UtilitiesOilAndGasSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Utilities: Oil &amp; Gas</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_IT_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Italy</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_IT_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ITALY</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIssuerAffiliationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Issuer Affiliation [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SediverSPAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sediver S p A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SediverSPAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sediver S.p.A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SediverSPAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sediver S.p.A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtWeightedAverageInterestRateOverTime_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtWeightedAverageInterestRateOverTime_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Weighted Average Interest Rate, over Time</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConsumerGoodsNon-DurableSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consumer Goods Non-Durable Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConsumerGoodsNon-DurableSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Consumer goods non-durable sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConsumerGoodsNon-DurableSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consumer goods: Non-durable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net expense for federal excise tax and other taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Expense For Federal Excise Tax And Other Taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net expense for U.S. federal excise tax and other taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HeritageEnvironmentalServicesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Heritage Environmental Services, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HeritageEnvironmentalServicesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Heritage environmental services, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HeritageEnvironmentalServicesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Heritage Environmental Services, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanDueAprilTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL FILO term loan due 4/2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanDueAprilTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">A B L F I L O Term Loan Due April Two Thousand Twenty Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanDueAprilTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">A B L F I L O Term Loan Due April Two Thousand Twenty Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Project44IncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Project44, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Project44IncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Project44 Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Project44IncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Project44, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentySevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due April two thousand twenty seven one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentySevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Seven One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentySevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan($45,000par,due4/2027)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Security Exchange Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Security Exchange Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit Facility [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain (Loss), Investment, Derivative, and Foreign Currency Transaction, Operating, after Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total net change in unrealized gains (losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net change in unrealized gains (losses) on investments and foreign currency translation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net change in unrealized gains (losses) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KryptonaBidCoUSLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Kryptona BidCo US, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KryptonaBidCoUSLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Kryptona BidCo US, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KryptonaBidCoUSLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Kryptona BidCo US, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Principal amount of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Outstanding Principal</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesAPreferredUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Series A Preferred Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesAPreferredUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Series A Preferred Units [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesAPreferredUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Series A preferred units.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SignalPeakCloLLCSeriesTwoThousandEighteenFiveAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Signal Peak CLO LLC, Series 2018-5A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SignalPeakCloLLCSeriesTwoThousandEighteenFiveAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Signal Peak Clo L L C, Series Two Thousand Eighteen Five A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SignalPeakCloLLCSeriesTwoThousandEighteenFiveAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Signal peak clo llc, series two thousand eighteen five A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($36,119 par, due 6/2029)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due June Two Thousand Twenty Nine [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due June two thousand twenty nine.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PrimeRevenueIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PrimeRevenue, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PrimeRevenueIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prime Revenue Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PrimeRevenueIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PrimeRevenue, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FoodAndBeverageSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Food and Beverage Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FoodAndBeverageSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Beverage &amp; Food</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ElysiumBidCoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Elysium BidCo Limited [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ElysiumBidCoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Elysium BidCo Limited.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ElysiumBidCoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Elysium BidCo Limited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJanuaryTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 1/2031</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJanuaryTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due January Two Thousand Thirty One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJanuaryTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured Product Due January Two Thousand Thirty One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentySevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due July two thousand twenty seven one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentySevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due July Two Thousand Twenty Seven One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentySevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($50,611 par, due 7/2027)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueNetAssetLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Fair Value, Net Asset (Liability), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueNetAssetLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Net Asset (Liability)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueNetAssetLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net assets, end of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityStatedMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Line of credit facility, stated maturity date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityStatedMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit Facility Stated Maturity Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityStatedMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, stated maturity date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IlluminateEducationIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Illuminate education, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IlluminateEducationIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Illuminate Education Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IlluminateEducationIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Illuminate Education, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Input Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAcquisitionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Initial Acquisition Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAcquisitionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Acquisition Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtCost_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments at amortized cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($68,950 par, Due 5/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due May Two Thousand Twenty Four One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due May Two Thousand Twenty Four One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConstructionAndBuildingSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Construction and Building Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConstructionAndBuildingSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Construction and building sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConstructionAndBuildingSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Construction &amp; Building</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TrustCertificatesOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Trust certificates one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TrustCertificatesOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Trust Certificates One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TrustCertificatesOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Trust Certificates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CifcCloLtdSeriesTwoThousandEighteenThreeAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">CIFC CLO Ltd, Series 2018-3A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CifcCloLtdSeriesTwoThousandEighteenThreeAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">CIFC CLO Ltd, Series Two Thousand Eighteen Three A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CifcCloLtdSeriesTwoThousandEighteenThreeAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">CIFC CLO Ltd, series two thousand eighteen three A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty twenty two convertible notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty Two Convertible Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022 Convertible Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Convertible Senior Notes Due 2022 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_BM_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Bermuda</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_BM_lbl" xlink:role="http://www.xbrl.org/2003/role/label">BERMUDA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValantMedicalSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Valant Medical Solutions, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValantMedicalSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Valant Medical Solutions, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValantMedicalSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valant Medical Solutions Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValantMedicalSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Valant Medical Solutions Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Paid, Excluding Capitalized Interest, Operating Activity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest paid during the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AgreementTerminationPeriodWithoutPenalty_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Agreement termination period, without penalty.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AgreementTerminationPeriodWithoutPenalty_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Agreement Termination Period Without Penalty</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AgreementTerminationPeriodWithoutPenalty_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Agreement termination period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NewportParentHoldingsLPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Newport Parent Holdings, LP.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NewportParentHoldingsLPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Newport Parent Holdings L P [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NewportParentHoldingsLPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Newport Parent Holdings, LP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MindBodyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">MindBody, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MindBodyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">MindBody, inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MindBodyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">MindBody, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GoldentreeCloLtdSeriesTwoThousandTwentySevenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">GoldenTree CLO Ltd, Series 2020-7A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GoldentreeCloLtdSeriesTwoThousandTwentySevenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">GoldenTree CLO Ltd, Series Two Thousand Twenty Seven A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GoldentreeCloLtdSeriesTwoThousandTwentySevenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">GoldenTree CLO Ltd, series two thousand twenty seven A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Document Period End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Period End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonControlledAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-controlled, affiliated investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonControlledAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non Controlled Affiliated Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonControlledAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-controlled, Affiliated Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 12/2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Seven One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Seven One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_DK_lbl" xlink:role="http://www.xbrl.org/2003/role/label">DENMARK</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_DK_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Denmark</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">West.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">West [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States - West</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanOctoberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Revolving Loan October Two Thousand Twenty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanOctoberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan October Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanOctoberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Revolving Loan ($3,000 par, Due 10/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WarrantOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WarrantOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrant one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WarrantOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrant One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Hierarchy and NAV</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RapidDataGmbhUnternehmensberatungMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Rapid Data GmbH Unternehmensberatung [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RapidDataGmbhUnternehmensberatungMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Rapid Data GmbH Unternehmensberatung.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RapidDataGmbhUnternehmensberatungMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Rapid Data GmbH Unternehmensberatung</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueOctoberTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 10/2031</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueOctoberTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due October Two Thousand Thirty One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueOctoberTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured Product Due October Two Thousand Thirty One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Gain (Loss), Investment, Derivative, and Foreign Currency Transaction, Operating, after Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total net realized gains (losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net realized gains (losses) on investments and foreign currency transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net Realized gains (losses) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIssuerAffiliationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Issuer Affiliation [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksRelatedToOurBusinessAndStructureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Risks Related to Our Business and Structure [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksRelatedToOurBusinessAndStructureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Risks Related to Our Business and Structure.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityExtendedDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Line of credit facility, extended date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityExtendedDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit Facility Extended Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityExtendedDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, extended date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, description of variable rate basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Description of Variable Rate Basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfFinancialPositionAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Financial Position [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvmetricsHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">InvMetrics Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvmetricsHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">InvMetrics Holdings, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvmetricsHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">InvMetrics holdings, inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q4SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2024 Q4 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q4SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2024 Q4 Supplemental Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q4SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q4 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwentyTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 3/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwentyTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-lien Loan Due March Twenty Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwentyTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due March Twenty Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IngenovisHealthFinanceLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ingenovis Health Finance, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IngenovisHealthFinanceLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ingenovis Health Finance, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IngenovisHealthFinanceLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ingenovis Health Finance, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_QuantrosIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Quantros, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_QuantrosIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Quantros, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_QuantrosIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Quantros, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of net proceeds of sale of equity interests.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Net Proceeds Of Sale Of Equity Interests</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of net proceeds of sale of equity interests</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BctoBluebillBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">BCTO Bluebill Buyer, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BctoBluebillBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BCTO Bluebill Buyer, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BctoBluebillBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BCTO Bluebill Buyer, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AlaskaBidcoOyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Alaska Bidco Oy [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AlaskaBidcoOyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Alaska bidco oy member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AlaskaBidcoOyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Alaska Bidco Oy</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementClassOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 10/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien loan Due October Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 10/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due October Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchaseProgramPeriodInForce1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock repurchase program period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchaseProgramPeriodInForce1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Repurchase Program, Period in Force</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonSharesClassBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Shares Class B</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonSharesClassBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Shares Class B [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonSharesClassBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common shares class B.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentAdvisoryAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment advisory agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentAdvisoryAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Advisory Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentAdvisoryAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment Advisory Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AmericanAchievementCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">American Achievement, Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AmericanAchievementCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">American Achievement Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AmericanAchievementCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">American Achievement Corp</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 4/2033</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due April Two Thousand Thirty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due April Two Thousand Thirty Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NondesignatedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Not Designated As Hedging Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NondesignatedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Not Designated as Hedging Instrument [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NondesignatedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">No Longer Designated As Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instruments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Offset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash collateral</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan due 5/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-Lien Loan Due May Two Thousand Twenty Four Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-Lien Loan Due 5/2024.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeOperatingTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income taxes, including excise taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeOperatingTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Operating, Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ShackeltonCloLtdSeries20157RaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shackelton CLO Ltd, Series 2015-7RA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ShackeltonCloLtdSeries20157RaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shackelton CLO Ltd, Series 2015-7RA [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ShackeltonCloLtdSeries20157RaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Shackelton CLO Ltd, Series 2015-7RA.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 5/2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due May Two Thousand Twenty Eight.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due May Two Thousand Twenty Eight [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="currency_AllCurrenciesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">All Currencies [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="currency_AllCurrenciesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">All Currencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanDueMayTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL FILO Term Loan due 5/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanDueMayTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ABL FILO Term Loan Due May Two Thousand Twenty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanDueMayTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">A B L F I L O Term Loan Due May Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanJuneTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Revolving Loan June Two Thousand Twenty Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanJuneTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan June Two Thousand Twenty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanJuneTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Revolving Loan ($12,327 par, Due 6/2022)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCash_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Restricted Cash, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCash_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCash_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DestinySolutionsParentHoldingCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Destiny Solutions Parent Holding Company.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DestinySolutionsParentHoldingCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Destiny Solutions Parent Holding Company [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DestinySolutionsParentHoldingCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Destiny Solutions Parent Holding Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from settlements of interest rate swaps excluding upfront fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Settlements Of Interest Rate Swaps Excluding Upfront Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from settlements of interest rate swaps excluding upfront fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Variable Rate [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured Product Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwentyTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan due 12/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwentyTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Twenty Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwentyTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan Due December Twenty Twenty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due October two thousand twenty five three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Five Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan (CAD 74,062 par, due 10/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ObligorGroupMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Obligor Group</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ObligorGroupMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Obligor Group [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income tax provision</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Gain (Loss), Investment and Derivative, Operating, Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Income tax provision</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Denominator for diluted weighted average shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average shares of common stock outstanding - diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_NO_lbl" xlink:role="http://www.xbrl.org/2003/role/label">NORWAY</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_NO_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Norway</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Reimbursement of transaction-related expenses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reimbursement Of Transaction Related Expenses [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reimbursement of Transaction-Related Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity File Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity File Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ElysianFincoLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Elysian Finco Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ElysianFincoLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Elysian Finco Ltd [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ElysianFincoLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Elysian Finco Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 4/2023</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due April Two Thousand Twenty Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeeExpenseCapitalGainBased_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fee Expense, Capital-Gain-Based</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeeExpenseCapitalGainBased_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net capital gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDecemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Revolving Loan due 12/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDecemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan December Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDecemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien revolving loan december two thousand twenty six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KasewareIntermediateHoldingCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Kaseware Intermediate Holding Company [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KasewareIntermediateHoldingCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Kaseware Intermediate Holding Company.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KasewareIntermediateHoldingCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Kaseware Intermediate Holding Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment fair value percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of investments at fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Investments At Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RainFocusLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">RainFocus, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RainFocusLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">RainFocus, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RainFocusLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">RainFocus, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CoverAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Cover [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CoverAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cover</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanJuneTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien revolving loan ($16,747 par, due 6/2023)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanJuneTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan June Two Thousand Twenty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanJuneTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Revolving Loan June Two Thousand Twenty Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesCTwoPreferredSharesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Series C-2 Preferred Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesCTwoPreferredSharesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Series C Two Preferred Shares [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesCTwoPreferredSharesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Series C-2 preferred shares.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValidityIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Validity, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValidityIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Validity Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValidityIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Validity Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross unrealized losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Tax Basis, Unrealized Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Estimated gross unrealized loss on tax cost investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ChemicalsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Chemicals</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ChemicalsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Chemicals [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ChemicalsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Chemicals.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_LU_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Luxembourg</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_LU_lbl" xlink:role="http://www.xbrl.org/2003/role/label">LUXEMBOURG</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 11/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due November Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due November Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JCPenneyCompanyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">J.C. Penney Company, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JCPenneyCompanyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">J.C. Penney Company Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JCPenneyCompanyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">J.C. Penney Company, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Input Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueOctoberTwoThousandThirtyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 10/2034</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueOctoberTwoThousandThirtyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due October Two Thousand Thirty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueOctoberTwoThousandThirtyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due October Two Thousand Thirty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value of Company's 2026 Notes, 2028 Notes, 2029 Notes and 2030 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest and dividend income recognition.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest and Dividend Income Recognition [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest and Dividend Income Recognition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JeffersonMillCloLtdSeriesTwoThousandFifteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Jefferson Mill CLO Ltd, Series 2015-1A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JeffersonMillCloLtdSeriesTwoThousandFifteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Jefferson Mill CLO Ltd, Series Two Thousand Fifteen One A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_JeffersonMillCloLtdSeriesTwoThousandFifteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Jefferson Mill CLO Ltd, series two thousand fifteen one A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BedBathAndBeyondIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Bed Bath and Beyond Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BedBathAndBeyondIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Bed Bath And Beyond Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BedBathAndBeyondIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Bed Bath and Beyond Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeCategorizationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeCategorizationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SubordinatedNoteDueSeptemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subordinated Note due 9/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SubordinatedNoteDueSeptemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Subordinated Note Due September Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SubordinatedNoteDueSeptemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subordinated Note Due September Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeGainLossOnDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in Unrealized Gains / (Losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeGainLossOnDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Gain (Loss) on Derivative, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeGainLossOnDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Derivative, Gain (Loss) on Derivative, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueMayTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First Lien Revolving Loan Due 5/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueMayTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien revolving loan due may two thousand twenty four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueMayTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan Due May Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioUnspecifiedDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scenario [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioUnspecifiedDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Scenario</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net change in unrealized (gains) losses on foreign currency transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain (Loss), Foreign Currency Transaction, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Translation of other assets and liabilities in foreign currencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($12,011 par, Due 12/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Five Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Five Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KkrCloLtdFortyNineAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">KKR CLO Ltd, 49A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KkrCloLtdFortyNineAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">KKR CLO Ltd, Forty Nine A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KkrCloLtdFortyNineAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">KKR CLO Ltd, forty nine A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SMPAHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">SMPA holdings, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SMPAHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">S M P A Holdings L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SMPAHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SMPA Holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q2BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2025 Q2 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q2BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2025 Q2 base dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q2BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2025 Q2 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AlternativeInvestmentMeasurementInput_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment measurement input</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AlternativeInvestmentMeasurementInput_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Alternative Investment, Measurement Input</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 12/2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Seven.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q4BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q4 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q4BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 Q4 Base Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q4BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q4 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Tax Basis, Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments owned estimated cost basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Tax cost of investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Tax cost of investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan (EUR 7,239 par, due 9/2028)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Eight [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan Due September Two Thousand Twenty Eight.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsDeclaredTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Dividends Declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsDeclaredTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Declared [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GeneralRiskFactorsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">General Risk Factors [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GeneralRiskFactorsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">General Risk Factors.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AvalaraIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Avalara, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AvalaraIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Avalara, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AvalaraIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Avalara, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealEstateSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Real Estate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealEstateSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Real Estate Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityOwnershipCapitalCommitmentAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Capital amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityOwnershipCapitalCommitmentAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Ownership Capital Commitment Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityOwnershipCapitalCommitmentAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity ownership capital commitment amount.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Adjustment in carrying value result from hedge accounting</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain (loss) on fair value effective hedge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Fair Value Hedge, Included in Effectiveness, Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StockRepurchaseProgramExpirationDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock repurchase program, expiration date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StockRepurchaseProgramExpirationDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Repurchase Program, Expiration Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Interest Rate During Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of management fee calculated on gross assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Management Fee Calculated On Gross Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of management fee on gross assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KangarooBidcoASMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Kangaroo Bidco A S [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KangarooBidcoASMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Kangaroo Bidco A S.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KangarooBidcoASMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Kangaroo Bidco AS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KangarooBidcoASMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Kangaroo Bidco AS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net realized (gains) losses on extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Gain (Loss) on Extinguishment of Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Extinguishment of Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PledgedStatusDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pledged Status [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PledgedStatusDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pledged Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OmnigoSoftwareLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Omnigo Software L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OmnigoSoftwareLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Omnigo Software L L C</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OmnigoSoftwareLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Omnigo software, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OmnigoSoftwareLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Omnigo Software, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfInvestmentsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Investments [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recent Accounting Standards and Regulatory Updates and Accounting Pronouncements Adopted in 2021</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">New Accounting Pronouncements, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueFebruaryTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 2/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueFebruaryTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-Lien Loan Due February Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueFebruaryTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-Lien Loan Due February Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum percentage of investment company taxable income distribute to stockholders in each taxable year to qualify as RIC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum Percentage Of Investment Company Taxable Income Distribute To Stockholders In Each Taxable Year To Qualify As R I C</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum percentage of investment company taxable income distribute to stockholders in each taxable year to qualify as RIC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ChangeInFairValueOfAnEffectiveHedge_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in fair value of an effective hedge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ChangeInFairValueOfAnEffectiveHedge_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change In Fair Value Of An Effective Hedge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ChangeInFairValueOfAnEffectiveHedge_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Change in fair value of an effective hedge.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MadisonParkFundingLtdSeriesTwoThousandFourteenFourteenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Madison Park Funding Ltd Series 2014-14A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MadisonParkFundingLtdSeriesTwoThousandFourteenFourteenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Madison Park Funding Ltd Series Two Thousand Fourteen Fourteen A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MadisonParkFundingLtdSeriesTwoThousandFourteenFourteenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Madison Park Funding Ltd Series Two Thousand Fourteen Fourteen A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Change in Unrealized Gain/(Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, at Fair Value, Net Change in Unrealized Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments in and advances to affiliates at fair value net change in unrealized gain (loss).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payment for Purchase, Investment, Operating Activity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchases and originations of investments, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_OwnershipAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ownership [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Disclosure Asset And Liability Not Measured At Fair Value [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GulfStreamMeridianSeriesTwoThousandTwentyOneFourAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gulf Stream Meridian, Series 2021-4A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GulfStreamMeridianSeriesTwoThousandTwentyOneFourAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gulf Stream Meridian, Series Two Thousand Twenty One Four A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GulfStreamMeridianSeriesTwoThousandTwentyOneFourAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Gulf Stream Meridian, series two thousand twenty one four A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyDividendDistribution_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Dividend Distribution</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyDividendDistribution_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Investment Company, Dividend Distribution, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyDividendDistribution_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends declared from distributable earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyDividendDistribution_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Dividends declared from distributable earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandAndThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand and Thirty Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandAndThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand and thirty notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandAndThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2030 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q3BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2025 Q3 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q3BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2025 Q3 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q3BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2025 Q3 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GainLossFormAdjustmentOfPaidInKindInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain Loss form Adjustment of Paid-in-kind Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GainLossFormAdjustmentOfPaidInKindInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Gain loss form adjustment of Paid-in-kind interest.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GainLossFormAdjustmentOfPaidInKindInterest_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Paid-in-kind interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfAnEffectiveHedge_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Fair value of an effective hedge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfAnEffectiveHedge_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value of an effective hedge.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfAnEffectiveHedge_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Of An Effective Hedge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfAnEffectiveHedge_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value of An Effective Hedge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Shares of common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Common Stock, Shares, Outstanding, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Common Stock, Shares, Outstanding, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common shares, outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NondeductibleFederalExciseTaxPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Nondeductible federal excise tax percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NondeductibleFederalExciseTaxPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nondeductible Federal Excise Tax Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NondeductibleFederalExciseTaxPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Nondeductible U.S. federal excise tax percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyThreeTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due September two thousand twenty three two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyThreeTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Three Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyThreeTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($86,466 par, due 9/2023)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TransportationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Transportation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TransportationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Transportation [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TransportationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transportation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Document Transition Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Transition Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due April two thousand twenty five four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Five Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan (EUR 9,070 par, due 4/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValuationTechniqueCostOfInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cost of Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValuationTechniqueCostOfInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Technique Cost of Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValuationTechniqueCostOfInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Valuation Technique Cost of Investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transfers within Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Within Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value measurement with unobservable inputs reconciliation recurring basis asset transfers within level 3.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($25,233 par, Due 10/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due October two thousand twenty four three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Four Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SportAllianceGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sport Alliance GMBH [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SportAllianceGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sport Alliance GMBH.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SportAllianceGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sport Alliance GmbH</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentDueDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment due date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentDueDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Due Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentDueDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment due date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueDiscountedCashFlowMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Discounted Cash Flow Model</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueDiscountedCashFlowMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Technique, Discounted Cash Flow [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfInvestmentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Investments [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net change in unrealized (gains) losses on interest rate swaps</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Unrealized gains (losses) on derivatives</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain (Loss) on Derivatives</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest rate swaps</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfCashFlowsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Cash Flows [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnfundedCommitments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unfunded Commitments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnfundedCommitments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Unfunded commitments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditsFacilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credits Facilities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditsFacilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving Credits Facilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditsFacilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facilities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CeltraTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Celtra Technologies, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CeltraTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Celtra Technologies Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CeltraTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Celtra Technologies, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_HK_lbl" xlink:role="http://www.xbrl.org/2003/role/label">HONG KONG</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_HK_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hong Kong</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock, net of offering and underwriting costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, New Issues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GcAgileHoldingsLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">GC Agile Holdings, Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GcAgileHoldingsLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">GC Agile Holdings, Ltd. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GcAgileHoldingsLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">GC agile holdings, Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FlightIntermediateHoldCoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Flight Intermediate HoldCo, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FlightIntermediateHoldCoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Flight Intermediate HoldCo, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FlightIntermediateHoldCoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Flight Intermediate HoldCo, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Unrealized loss on investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Loss On Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross unrealized losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of pre-incentive fee net investment income, annualized after catch-up achieved.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Pre Incentive Fee Net Investment Income Annualized After Catch Up Achieved</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of pre-Incentive Fee net investment income annualized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TradingSecuritiesDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Trading Securities Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TradingSecuritiesDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Trading</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TradingSecuritiesDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FactorSystemsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Factor Systems, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FactorSystemsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Factor Systems, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FactorSystemsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Factor systems, inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien revolving loan due 10/2022</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan Due October Two Thousand Twenty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien revolving loan due october two thousand twenty two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NumberOfPortfolioCompanies_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of portfolio companies in SCP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NumberOfPortfolioCompanies_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Portfolio Companies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NumberOfPortfolioCompanies_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of portfolio companies.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BtrsHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BTRS Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BtrsHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BTRS Holdings, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BtrsHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">BTRS Holdings, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeePayableCapitalGainBased_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fee Payable, Capital-Gain-Based</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeePayableCapitalGainBased_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net capital gains accrued to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($1,363 par, due 9/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan Due September Two Thousand Twenty Six One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Six One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementFeeWaiverHurdle_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of asset coverage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementFeeWaiverHurdle_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Management Fee Waiver Hurdle</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementFeeWaiverHurdle_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Management fee waiver hurdle.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien revolving loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First Lien Revolving Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance, End of Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance, beginning of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Operating, after Expense and Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WhiteboxCloILtdSeriesTwoThousandTwentyTwoAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Whitebox CLO I Ltd, Series 2020-2A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WhiteboxCloILtdSeriesTwoThousandTwentyTwoAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Whitebox Clo I Ltd, Series Two Thousand Twenty Two A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WhiteboxCloILtdSeriesTwoThousandTwentyTwoAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Whitebox clo i ltd, series two thousand twenty two A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Net Assets Resulting from Operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanDueMayTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL FILO Term Loan due 5/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanDueMayTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ABL FILO Term Loan Due May Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanDueMayTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ABL FILO term loan due may two thousand twenty four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GalileoParentincMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Galileo Parent, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GalileoParentincMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Galileo Parent Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GalileoParentincMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Galileo Parent Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherInvestmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other investment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherInvestmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Investment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherInvestmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other Investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherInvestmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Other Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeriesEPreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Series E Preferred Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeriesEPreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Series E Preferred Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IbisUSBlockerCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ibis US Blocker Co.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IbisUSBlockerCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ibis U S Blocker Co [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IbisUSBlockerCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ibis US Blocker Co.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeverageWaiverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Leverage waiver.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeverageWaiverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leverage Waiver [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeverageWaiverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leverage Waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PartnershipInterestOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Partnership/Membership interest of ownership</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PartnershipInterestOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Partnership Interest Ownership Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PartnershipInterestOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Partnership interest ownership percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 7/2022</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due July Two Thousand Twenty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due July two thousand twenty two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentBasisSpreadVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reference Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentBasisSpreadVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Basis Spread, Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EatonCloLtdSeriesTwoThousandTwentyOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Eaton CLO Ltd, Series 2020-1A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EatonCloLtdSeriesTwoThousandTwentyOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Eaton Clo Ltd Series Two Thousand Twenty One A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EatonCloLtdSeriesTwoThousandTwentyOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Eaton clo ltd series two thousand twenty one A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q1SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2025 Q1 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q1SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2025 Q1 supplemental dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q1SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2025 Q1 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProjectPIntermediate2LLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Project P Intermediate 2, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProjectPIntermediate2LLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Project P Intermediate2 L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProjectPIntermediate2LLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Project P Intermediate 2, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransportationSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Transportation Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransportationSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transportation: Cargo</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EdgeBidcoBVMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Edge Bidco B V [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EdgeBidcoBVMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Edge Bidco B.V.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EdgeBidcoBVMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Edge Bidco B.V.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Prepaid Expense and Other Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Prepaid expenses and other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NmgParentLlcComUnitMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">NMG Parent LLC Com Unit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NmgParentLlcComUnitMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">NMG Parent LLC Com Unit [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NmgParentLlcComUnitMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">NMG Parent LLC Com Unit.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized Gain/(Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, at Fair Value, Realized Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments in and advances to affiliates at fair value net realized gain loss.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyTwoOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due august two thousand twenty two one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyTwoOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due August Two Thousand Twenty Two One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyTwoOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan($62,725par,due8/2022)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Document Fiscal Year Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Year Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableNature_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableNature_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Nature</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SwapSettlement_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Swap settlement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SwapSettlement_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Swap settlement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SwapSettlement_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Swap Settlement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Change in Unrealized Gains or Losses on Investments for Which Level 3 Inputs were Used in Determining Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AsgIiLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ASG II, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AsgIiLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ASG II, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AsgIiLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ASG II, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BtrsHoldingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">BTRS Holding Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BtrsHoldingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BTRS Holding Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BtrsHoldingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BTRS Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due December two thousand twenty seven three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Seven Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan (CAD 55,042 par, due 12/2027)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnfundedLoanCommitmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unfunded Loan Commitment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnfundedLoanCommitmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unfunded Loan Commitments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NmgHoldingCompanyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">NMG Holding Company, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NmgHoldingCompanyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">NMG Holding Company Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NmgHoldingCompanyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">NMG Holding Company, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MississippiResourcesLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Mississippi Resources, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MississippiResourcesLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Mississippi Resources L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MississippiResourcesLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Mississippi Resources, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFourOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($8,775 par, Due 12/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFourOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due December two thousand twenty four one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFourOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Four One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel">Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments for (Proceeds from) Hedge, Investing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HigherLogicLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Higher Logic, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HigherLogicLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Higher Logic L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HigherLogicLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Higher Logic, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First Lien loan Due 6/2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due June Two Thousand Twenty Eight [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan Due June Two Thousand Twenty-Eight.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeMaturityDates_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Maturity Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeMaturityDates_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative maturity date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeMaturityDates_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Contract End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NeuintelLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Neuintel, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NeuintelLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Neuintel L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NeuintelLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Neuintel, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FinancialServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Financial services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FinancialServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FinancialServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of minimum qualifying assets to purchase non-qualifying assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Minimum Qualifying Assets To Purchase Non Qualifying Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of minimum qualifying assets to purchase non qualifying assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeBasisSpreadOnVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative, basis spread on variable rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeBasisSpreadOnVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Basis Spread on Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HippoXpaBidcoAbMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hippo XPA Bidco AB</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HippoXpaBidcoAbMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hippo XPA Bidco AB [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HippoXpaBidcoAbMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hippo XPA Bidco AB</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EMSLinqIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">EMS Linq, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EMSLinqIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">E M S Linq Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EMSLinqIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">E M S Linq Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EMSLinqIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">EMS Linq, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PrimePayIntermediateLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PrimePay Intermediate, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PrimePayIntermediateLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prime Pay Intermediate L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PrimePayIntermediateLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PrimePay Intermediate, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PrimePayIntermediateLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Primepay Intermediate, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Second-lien debt investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Second Lien Debt Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Second-lien Debt Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, Other Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments in and advances to affiliates, other income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Incentive fees realized and payable to advisor</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive fees on net investment income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fees On Net Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MembershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Membership Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MembershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Membership Interest [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MembershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Membership interest.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesAaPreferredStockWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Series AA Preferred Stock Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesAaPreferredStockWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Series AA Preferred Stock Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesAaPreferredStockWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Series AA Preferred Stock Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 10/2023</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due october two thousand twenty three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payments for settlements of interest rate swaps excluding upfront fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments For Settlements Of Interest Rate Swaps Excluding Upfront Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payments for settlements of interest rate swaps excluding upfront fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Investment Income Before Income Taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Liabilities, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other payables to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJanuaryTwoThousandThirtySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 1/2037</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJanuaryTwoThousandThirtySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due January Two Thousand Thirty Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJanuaryTwoThousandThirtySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due january two thousand thirty seven.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_CA_lbl" xlink:role="http://www.xbrl.org/2003/role/label">CANADA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_CA_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Canada</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WarrantTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WarrantTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrant two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WarrantTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrant Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril242029Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility Maturity On April 24, 2029 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril242029Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving credit facility maturity on April 24, 2029.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril242029Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility Maturity On April 24, 2029</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyDistributionToShareholdersPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Distribution to Shareholders, Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyDistributionToShareholdersPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends declared from net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyDistributionToShareholdersPerShare_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Dividends declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EatonCloLtdSeriesTwoThousandFifteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Eaton CLO Ltd, Series 2015-1A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EatonCloLtdSeriesTwoThousandFifteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Eaton CLO Ltd, Series Two Thousand Fifteen One A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EatonCloLtdSeriesTwoThousandFifteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Eaton CLO Ltd, series two thousand fifteen one A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MembersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Members' Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MembersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Members' Equity, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MembersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Members equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TherapeuticsMDIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">TherapeuticsMD, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TherapeuticsMDIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">TherapeuticsMD, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TherapeuticsMDIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Therapeutics M D Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Net Assets, Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Percentage of net assets percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit, outstanding amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Line of Credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Long-Term Line of Credit, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentRiskAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Instrument [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentRiskAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetAssetsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net Assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetAssetsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Assets Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetAssetsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial and Derivative Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivatives, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PurchaseCommitmentToFundInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Purchase commitment to fund investment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PurchaseCommitmentToFundInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Purchase Commitment To Fund Investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PurchaseCommitmentToFundInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Portfolio Company Commitments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 7/2032</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due July Two Thousand Thirty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due July Two Thousand Thirty Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RailAcquisitionsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Rail Acquisitions LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RailAcquisitionsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Rail Acquisitions L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RailAcquisitionsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Rail acquisitions L L C.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IntegrationApplianceIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Integration Appliance, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IntegrationApplianceIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Integration Appliance, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IntegrationApplianceIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Integration appliance, inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonRule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non Rule 10b5 1Arr Modified [Flag]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonRule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non Rule 10b5 1arrangement modified.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonRule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-Rule 10b5-1 Arrangement Modified</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OpenSwapContractIdentifierAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Open Swap Contract, Identifier [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarvalCloIiiLtdSeriesTwoThousandNineteenTwoAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">CarVal CLO III Ltd, Series 2019-2A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarvalCloIiiLtdSeriesTwoThousandNineteenTwoAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">CarVal CLO III Ltd, Series Two Thousand Nineteen Two A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarvalCloIiiLtdSeriesTwoThousandNineteenTwoAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">CarVal CLO III Ltd, series two thousand nineteen two A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Title of 12(b) Security</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Title of 12(b) Security</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Interest Rate at Period End</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, base rate percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueJanuaryTwoThousandAndTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien revolving loan, due 1/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueJanuaryTwoThousandAndTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan Due January Two thousand and Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueJanuaryTwoThousandAndTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Revolving Loan Due 1/2024.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Instruments and Hedging Activities Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivatives</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AbsorbSoftwareIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Absorb Software, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AbsorbSoftwareIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Absorb Software, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AbsorbSoftwareIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Absorb Software, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SkyBidcoSPAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sky Bidco S.p.A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SkyBidcoSPAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sky Bidco S.p.A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SkyBidcoSPAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sky Bidco S.p.A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGroupMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Carlyle Group [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGroupMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carlyle Group.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGroupMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Carlyle Group</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGroupMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Carlyle</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedInvestmentsPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Investments, Percent of Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedInvestmentsPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value of securities as percentage of net assets in percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanOneDueAprilTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL FILO Term Loan due 4/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanOneDueAprilTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ABL FILO Term Loan One Due April Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFiloTermLoanOneDueAprilTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ABL FILO Term Loan One Due April Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related and Nonrelated Parties [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Management Fee in Excess of Quarter Rate on Gross Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of management fee in excess of quarter rate on gross assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of management fee in excess of quarter rate on gross assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 7/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due July Two Thousand Twenty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due July Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OfficeProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Office Products.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OfficeProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Office Products [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OfficeProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Office Products</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LynxBidcoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lynx BidCo</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LynxBidcoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lynx BidCo [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LynxBidcoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lynx bidCo.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommunicationsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Communications.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommunicationsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Communications [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommunicationsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Communications</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ConsolidatedEntitiesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consolidated Entities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ConsolidatedEntitiesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidated Entities [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseRatioVoluntaryFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ratio of net expenses to average net asset, excluding waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseRatioVoluntaryFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Expense Ratio, Voluntary Fee Waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LegalEntityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Legal Entity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 10/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due October Two Thousand Twenty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Changes in operating assets and liabilities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixSevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due September two thousand twenty six seven.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixSevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Six Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixSevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($22,730 par, due 9/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 4/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due April Two Thousand Twenty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LettersOfCreditOutstandingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Letters of Credit Outstanding, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LettersOfCreditOutstandingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of letters of credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyThreeOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due April two thousand twenty three one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyThreeOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Three One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyThreeOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan($59,318par,due4/2023)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TrustCertificatesTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Trust certificates two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TrustCertificatesTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Trust Certificates Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TrustCertificatesTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Trust Certificates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of excess pre-incentive fee net investment income payable after hurdle rate reached and catch-up achieved.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Excess Pre Incentive Fee Net Investment Income Payable After Hurdle Rate Reached And Catch Up Achieved</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of excess pre-Incentive Fee net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Recurring and Nonrecurring [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienTermLoanDueDecemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Term Loan due 12/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienTermLoanDueDecemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Term Loan Due December Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienTermLoanDueDecemberTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien term loan due december two thousand twenty six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid-in Capital [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Paid in Capital in Excess of Par</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ApteanIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aptean Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ApteanIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aptean Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ApteanIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aptean, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienTermLoanDueSeptemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Term Loan due 9/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienTermLoanDueSeptemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Term Loan Due September Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienTermLoanDueSeptemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien term loan due september two thousand twenty five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of incentive fee rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Capital Gains From April 1 2024 Hurdle Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of capital gains from April 1, 2024 hurdle rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_GB_lbl" xlink:role="http://www.xbrl.org/2003/role/label">UNITED KINGDOM</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_GB_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United Kingdom</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StockRepurchaseProgramAuthorizedAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock repurchase program, authorized amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StockRepurchaseProgramAuthorizedAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Repurchase Program, Authorized, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Income Location, Balance [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in accounting principle, accounting standards update, adoption date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change in Accounting Principle, Accounting Standards Update, Adoption Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Trading Symbol</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Trading Symbol</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt and Equity Securities, Unrealized Gain (Loss), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt and Equity Securities, Unrealized Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Unrealized Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Related Party Transactions By Related Party [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFirstLienLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ABL first-lien loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFirstLienLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">A B L First Lien Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFirstLienLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL First-Lien Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 4/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due April Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 12/2021</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due december two thousand twenty one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ExtraHopNetworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ExtraHop Networks, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ExtraHopNetworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Extra Hop Networks Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ExtraHopNetworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ExtraHop Networks Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndOtherInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity and Other Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndOtherInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity and other investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndOtherInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity And Other Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Financial Highlights [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Realized capital gains accrued beginning April 1, 2014.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Capital Gains Accrued Beginning April First Two Thousand Fourteen [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized Capital Gains Accrued Beginning April 1, 2014</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Flows from Financing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Unused Capacity, Commitment Fee Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, undrawn amount percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AxonifyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Axonify, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AxonifyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Axonify Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AxonifyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Axonify, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Equity Method Investments [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksRelatedToEconomicConditionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Risks Related to Economic Conditions [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksRelatedToEconomicConditionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Risks Related to Economic Conditions.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFirstLienLoanDueAugustTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL First-lien Loan due 8/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFirstLienLoanDueAugustTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ABL First Lien Loan Due August Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblFirstLienLoanDueAugustTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ABL first lien loan due august two thousand twenty five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement Inputs and Valuation Techniques [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due October two thousand twenty four four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Four Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan($35,000par,due10/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndDebtExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Interest Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndDebtExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest and Debt Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndDebtExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Interest Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($13,848 par, Due 7/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due July Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due July Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">First-lien Loan due 11/2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Six Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Six Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($53,100 par, Due 12/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TransportationConsumerSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Transportation Consumer Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TransportationConsumerSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Transportation consumer sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TransportationConsumerSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transportation: Consumer</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Components [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Components</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PassportLabsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Passport Labs, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PassportLabsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Passport Labs Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PassportLabsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Passport Labs, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StewartParkCloLtdSeriesTwoThousandFifteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stewart Park CLO Ltd, Series 2015-1A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StewartParkCloLtdSeriesTwoThousandFifteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stewart Park Clo Ltd, Series Two Thousand Fifteen One A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StewartParkCloLtdSeriesTwoThousandFifteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Stewart park clo ltd, series two thousand fifteen one A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFourOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due April two thousand twenty four one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFourOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Four One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFourOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan($11,205par,due4/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AVSCHoldingCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">AVSC Holding Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AVSCHoldingCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">AVSC Holding Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AVSCHoldingCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">AVSC Holding Corp</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 8/2023</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due August Two Thousand Twenty Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due August two thousand twenty three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Offsetting assets and liabilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Offsetting Assets And Liabilities [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Offsetting Assets and Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WindRiverCloLtdSeries20142AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Wind River CLO Ltd, Series 2014-2A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WindRiverCloLtdSeries20142AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Wind River CLO Ltd, Series 2014-2A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WindRiverCloLtdSeries20142AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Wind River CLO Ltd, Series 2014-2A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Component [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Component</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien loan due September two thousand twenty six four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Six Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($68,160 par, due 9/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends to Common Stockholders</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityStructuredCreditAndJointVentureInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Structured Credit and Joint Venture Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityStructuredCreditAndJointVentureInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity Structured Credit and Joint Venture Investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityStructuredCreditAndJointVentureInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity, Structured Credit and Joint Venture Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due July two thousand twenty five one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due July Two Thousand Twenty Five One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJulyTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan($50,332par,due7/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentOwnedParValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment owned par value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentOwnedParValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned Par Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentOwnedParValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment owned par value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Financial Highlights [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Highlights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien debt investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Debt Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Debt Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Investments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Remaining investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Investments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Investments_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Investments, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGlobalMarketStrategiesCloLtdSeriesTwoThousandFourteenFourRaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Carlyle Global Market Strategies CLO Ltd, Series 2014-4RA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGlobalMarketStrategiesCloLtdSeriesTwoThousandFourteenFourRaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Carlyle Global Market Strategies CLO Ltd Series Two Thousand Fourteen Four RA [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGlobalMarketStrategiesCloLtdSeriesTwoThousandFourteenFourRaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carlyle Global Market Strategies CLO Ltd Series Two Thousand Fourteen-Four RA.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MurchisonOilAndGasLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Murchison Oil and Gas, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MurchisonOilAndGasLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Murchison Oil and Gas, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MurchisonOilAndGasLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Murchison Oil and Gas, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Investment Income (Loss), Per Share, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueOfDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Derivative, fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueOfDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Derivative, Fair Value, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueOfDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Fair Value, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueOfDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total derivatives</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MDAmericaEnergyLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">MD America Energy, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MDAmericaEnergyLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">MD America Energy LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MDAmericaEnergyLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">M D America Energy L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OzlmLtdSeriesTwoThousandEighteenEighteenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">OZLM Ltd., Series 2018-18 A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OzlmLtdSeriesTwoThousandEighteenEighteenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">OZLM Ltd., Series Two Thousand Eighteen Eighteen A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OzlmLtdSeriesTwoThousandEighteenEighteenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">OZLM Ltd., Series Two Thousand Eighteen Eighteen A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Thirty Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty Thirty Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">2030 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2030 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyIssuanceOfSharesPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Share Issuance, Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyIssuanceOfSharesPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock, net of offering costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of pre-incentive fee net investment income payable quarterly.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Pre Incentive Fee Net Investment Income Payable Quarterly</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of total pre-Incentive fee net investment income payable quarterly</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Income [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WorkwellAcquisitionCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Workwell Acquisition Co.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WorkwellAcquisitionCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Workwell Acquisition Co [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WorkwellAcquisitionCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Workwell Acquisition Co.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Revolving Loan due 4/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Revolving Loan April Two Thousand Twenty Five One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan April Two Thousand Twenty Five One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Method Investment, Nonconsolidated Investee [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendPayableDateToBePaidDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Date to be Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendPayableDateToBePaidDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payment Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Instrument, Increase (Decrease), Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Increase (Decrease), Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase (decrease) in carrying value of notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourSwapTransactionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 Swap Transaction [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourSwapTransactionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Four Swap Transaction [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourSwapTransactionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty four swap transaction.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DesignatedAsHedgingInstrumentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Designated as Hedging Instrument [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DesignatedAsHedgingInstrumentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Designated As Hedging Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleSecuredLendingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Carlyle Secured Lending, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleSecuredLendingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Carlyle Secured Lending, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleSecuredLendingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carlyle Secured Lending, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LexipolLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lexipol, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LexipolLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lexipol, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LexipolLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lexipol, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PianoSoftwareIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Piano Software, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PianoSoftwareIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Piano Software Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PianoSoftwareIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Piano Software, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoansDueDecemberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loans Due December Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoansDueDecemberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loans Due December Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoansDueDecemberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($8,775 par, due 12/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ErlingLuxBidcoSarlMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Erling Lux Bidco SARL</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ErlingLuxBidcoSarlMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Erling Lux Bidco SARL [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ErlingLuxBidcoSarlMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Erling Lux Bidco SARL.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetailSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retail Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetailSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Retail</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Value, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, $0.01 par value; 400,000,000 shares authorized, 95,683,850 and 95,369,400 shares issued, respectively; and 95,019,600 and 94,705,150 shares outstanding, respectively</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfGeographicCompositionOfJointVentureInvestmentsPortfolioAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Geographic Composition of Joint Venture Investments Portfolio at Fair Value [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfGeographicCompositionOfJointVentureInvestmentsPortfolioAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of geographic composition of joint venture investments portfolio at fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfGeographicCompositionOfJointVentureInvestmentsPortfolioAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Geographic Composition of SCP's Portfolio at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AcceoSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Acceo Solutions, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AcceoSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Acceo Solutions Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AcceoSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Acceo Solutions Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BiohavenPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Biohaven Pharmaceuticals, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BiohavenPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Biohaven Pharmaceuticals Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BiohavenPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Biohaven Pharmaceuticals, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BenNevisMidcoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ben Nevis Midco Limited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BenNevisMidcoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ben Nevis Midco Limited [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BenNevisMidcoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ben nevis midco limited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BayshoreIntermediate2LPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Bayshore Intermediate #2, L.P.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BayshoreIntermediate2LPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Bayshore Intermediate2 L P [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BayshoreIntermediate2LPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Bayshore Intermediate #2, LP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Expiration Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, expiration date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q1SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023 Q1 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q1SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023 Q1 supplemental dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q1SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023 Q1 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HealthcareSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Healthcare Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HealthcareSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Healthcare</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HealthcareSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Healthcare &amp; Pharmaceuticals</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Income taxes, including excise taxes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Taxes Including Excise Taxes [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes, Including Excise Taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AvidXchangeIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">AvidXchange, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AvidXchangeIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Avid Xchange Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AvidXchangeIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">AvidXchange, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJanuaryTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 1/2030</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJanuaryTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due January two thousand thirty.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJanuaryTwoThousandThirtyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due January Two Thousand Thirty [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfWeightedAverageNumberOfSharesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Weighted Average Number of Shares [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfWeightedAverageNumberOfSharesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Computation of Basic and Diluted Earnings Per Common Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CrewlineBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Crewline Buyer, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CrewlineBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Crewline Buyer, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CrewlineBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Crewline Buyer, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amortization of Debt Issuance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization of deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueMarchTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($37,500 par, due 3/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueMarchTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan one Due March Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueMarchTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan one Due March Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Realized capital gains accrued prior to March 31, 2014.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Capital Gains Accrued Prior To March Thirty First Two Thousand Fourteen [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized Capital Gains Accrued Prior to March 31, 2014</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnMay12026Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility Maturity On May 1, 2026 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnMay12026Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving Credit Facility Maturity On May 1, 2026.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnMay12026Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility Maturity On May 1 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueMayTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 5/2031</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueMayTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due May Two Thousand Thirty One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueMayTwoThousandThirtyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due May Two Thousand Thirty One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourTwentySixTwentyEightTwentyNineAndTwentyThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Four Twenty Six Twenty Eight Twenty Nine And Twenty Thirty Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourTwentySixTwentyEightTwentyNineAndTwentyThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty four twenty six twenty eight twenty nine and twenty thirty notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourTwentySixTwentyEightTwentyNineAndTwentyThirtyNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 Notes, 2026 Notes, 2028 Notes, 2029 Notes and 2030 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WideOrbitIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">WideOrbit, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WideOrbitIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Wide Orbit Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WideOrbitIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">WideOrbit, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityInvestmentBasisSpreadVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Investment Basis Spread Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityInvestmentBasisSpreadVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity investment basis spread variable rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityInvestmentBasisSpreadVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reference Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DrydenSeniorLoanFundSeriesTwoThousandEighteenFiftyFiveAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dryden Senior Loan Fund, Series 2018-55A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DrydenSeniorLoanFundSeriesTwoThousandEighteenFiftyFiveAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dryden Senior Loan Fund Series Two Thousand Eighteen Fifty Five A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DrydenSeniorLoanFundSeriesTwoThousandEighteenFiftyFiveAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dryden senior loan fund, series 2018-55A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfIncentiveFeeRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fee rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfIncentiveFeeRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of incentive fee rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfIncentiveFeeRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Incentive Fee Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Debt [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Debt Obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesCOnePreferredSharesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Series C-1 preferred shares.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesCOnePreferredSharesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Series C One Preferred Shares [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SeriesCOnePreferredSharesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Series C-1 Preferred Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DrydenSeniorLoanFundSeriesTwoThousandTwentyEightySixAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dryden Senior Loan Fund, Series 2020-86A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DrydenSeniorLoanFundSeriesTwoThousandTwentyEightySixAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dryden Senior Loan Fund Series Two Thousand Twenty Eighty Six A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DrydenSeniorLoanFundSeriesTwoThousandTwentyEightySixAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dryden senior loan fund, series 2020-86A .</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 12/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_FR_lbl" xlink:role="http://www.xbrl.org/2003/role/label">FRANCE</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_FR_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">France</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDividendsPayableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Dividends Payable [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDividendsPayableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Dividends Declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnderlyingAssetClassAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Underlying Asset Class [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnderlyingAssetClassAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Underlying Asset Class</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RiskonnectIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Riskonnect, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RiskonnectIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Riskonnect Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RiskonnectIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Riskonnect, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AstraAcquisitionCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Astra acquisition Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AstraAcquisitionCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Astra Acquisition Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AstraAcquisitionCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Astra Acquisition Corp</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Transaction [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 10/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due October Two Thousand Twenty Four One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Four One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Registrant Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Registrant Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transfers into (out of) Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WindRiverCloLtdSeriesTwoThousandSeventeenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Wind River CLO Ltd, Series 2017-1A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WindRiverCloLtdSeriesTwoThousandSeventeenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Wind River Clo Ltd Series Two Thousand Seventeen One A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WindRiverCloLtdSeriesTwoThousandSeventeenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Wind river clo ltd series two thousand seventeen one A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockSharesAcquired_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchases of treasury stock, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockSharesAcquired_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Number of shares repurchased</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockSharesAcquired_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchases of treasury stock, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockSharesAcquired_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Shares, Acquired</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeriesDPreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Series D Preferred Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeriesDPreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Series D Preferred Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">2026 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty six notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Six Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2026 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WeightedAverageYieldOnSeniorSecuredLoansAtAmortizedCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Yield on Senior Secured Loans at Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WeightedAverageYieldOnSeniorSecuredLoansAtAmortizedCost_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Weighted average yield on senior secured loans at amortized cost.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WeightedAverageYieldOnSeniorSecuredLoansAtAmortizedCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average yield on senior secured loans at amortized cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Controlled, Affiliated Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Affiliated Issuer, Controlled [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SOFR</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ConsolidatedEntitiesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidated Entities [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ConsolidatedEntitiesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consolidated Entities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Shares Newly Issued to Shareholders Who Have Not Opted Out of Dividend Reinvestment Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of shares newly issued to shareholders who have not opted out of dividend reinvestment plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary of Shares Newly Issued to Shareholders Who Have Not Opted Out of Dividend Reinvestment Plan [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArrowbuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Arrow Buyer, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArrowbuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Arrow Buyer, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArrowbuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Arrow Buyer, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Proceeds From Issuance Of Common Stock, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Issuance of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from issuance of common stock, net of offering and underwriting costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Cash proceeds from issuance of common stock, net of offering and underwriting fees and offering costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Repayments / redemptions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value of Level 3 Investments at Fair Value and Significant Unobservable Inputs Used in Valuations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-Lien Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Non-controlling investments percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsidiary, Ownership Percentage, Noncontrolling Owner</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Common Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Common Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrganizationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Organization policy.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrganizationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrganizationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Organization</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WeightedAverageYieldOnSeniorSecuredLoansAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Yield on Senior Secured Loans at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WeightedAverageYieldOnSeniorSecuredLoansAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Weighted average yield on senior secured loans at fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WeightedAverageYieldOnSeniorSecuredLoansAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average yield on senior secured loans at fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxAssetsPertainingToNetUnrealizedGainsRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Pertaining To Net Unrealized Gains Related To Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxAssetsPertainingToNetUnrealizedGainsRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred tax assets pertaining to net unrealized gains related to investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxAssetsPertainingToNetUnrealizedGainsRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax asset pertaining to net unrealized gains related to investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SouthwickParkCloLtdSeries20194AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Southwick Park CLO Ltd, Series 2019-4A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SouthwickParkCloLtdSeries20194AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Southwick Park CLO Ltd, Series 2019-4A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SouthwickParkCloLtdSeries20194AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Southwick Park CLO Ltd, Series 2019-4A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WeightedAverageYieldOnPrincipalAmountOfOutstandingDebtInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Yield on Principal Amount of Outstanding Debt Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WeightedAverageYieldOnPrincipalAmountOfOutstandingDebtInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Weighted average yield on principal amount of outstanding debt investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WeightedAverageYieldOnPrincipalAmountOfOutstandingDebtInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average yield on principal amount of outstanding debt investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q1BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q1 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q1BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 Q1 Base dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q1BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q1 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due March two thousand twenty four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due March Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMarchTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($30,000 par, due 3/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TradingScreenIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">TradingScreen, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TradingScreenIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Trading Screen Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TradingScreenIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">TradingScreen, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueFebruaryTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($1,363 par, due 9/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueFebruaryTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due February Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueFebruaryTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due February Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetAssetValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Net Asset Value, End of Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetAssetValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Net asset value, beginning of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetAssetValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net Asset Value per Share as of the End of the Quarter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetAssetValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Asset Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty Nine Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty twenty nine notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2029 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Financing Receivable [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Financing Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblDipTermLoanDueAprilTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL DIP term loan due 4/2021</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblDipTermLoanDueAprilTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ABL DIP Term Loan Due April Two Thousand Twenty One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AblDipTermLoanDueAprilTwoThousandTwentyOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ABL DIP term loan due april two thousand twenty one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RatioOfIndebtednessToNetCapital1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ratio of Indebtedness to Net Capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RatioOfIndebtednessToNetCapital1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset coverage ratio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CordanceOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cordance Operations, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CordanceOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cordance Operations LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CordanceOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cordance Operations, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Equity Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EducationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Education.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EducationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Education [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EducationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Education</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Income Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Income Tax Expense (Benefit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax benefit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Deferred tax benefit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_WeightedAverageMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_WeightedAverageMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of geographic composition of investments at fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Geographic Composition Of Investments At Fair Value [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Geographic Composition of Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 6/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due June Two Thousand Twenty Six One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due June Two Thousand Twenty Six One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReliaQuestHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ReliaQuest Holdings, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReliaQuestHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Relia Quest Holdings L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReliaQuestHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ReliaQuest Holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MarcuraEquitiesLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Marcura Equities LTD [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MarcuraEquitiesLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Marcura Equities LTD.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MarcuraEquitiesLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Marcura Equities LTD</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetCoveragePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Asset coverage percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetCoveragePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Coverage Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetCoveragePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset coverage percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeantaasHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">LeanTaaS Holdings Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeantaasHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">LeanTaaS Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeantaasHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">LeanTaaS Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2028 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Eight Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty eight notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanDueAprilTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL FILO Term Loan due 4/2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanDueAprilTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ABL FILO Term Loan Due April Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanDueAprilTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">A B L F I L O Term Loan Due April Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyEightOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due may two thousand twenty eight one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyEightOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due May Two Thousand Twenty Eight One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyEightOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan($12,669par,due5/2028)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Issuance of common stock, net of offering and underwriting costs, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, New Issues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueMayTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Convertible Note due 5/2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueMayTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Convertible Note Due May Two Thousand Twenty Eight.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueMayTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Convertible Note Due May Two Thousand Twenty Eight [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MidwestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Midwest.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MidwestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Midwest [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MidwestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States - Midwest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Diluted, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings per common share - diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EDBParentLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">EDB Parent, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EDBParentLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">E D B Parent L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EDBParentLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">EDB Parent, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInInterestReceivablePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in interest receivable paid-in-kind.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInInterestReceivablePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Interest Receivable Paid In Kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInInterestReceivablePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest receivable paid-in-kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">City Area Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">City Area Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Octagon57LlcSeries20211AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Octagon 57 LLC, Series 2021-1A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Octagon57LlcSeries20211AMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Octagon 57 LLC, Series 2021-1A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GTreasurySSLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">G Treasury SS, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GTreasurySSLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">G Treasury S S L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GTreasurySSLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">G Treasury SS, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AfsTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">AFS Technologies, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AfsTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">AFS Technologies, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AfsTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">AFS Technologies, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConsumerGoodsDurableSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consumer Goods Durable Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConsumerGoodsDurableSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Consumer goods durable sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConsumerGoodsDurableSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consumer goods: Durable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Face Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate principal amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Aggregate Principal Amount Committed</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NintexGlobalLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Nintex Global, Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NintexGlobalLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nintex Global, Ltd [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NintexGlobalLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Nintex global, ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility maximum borrowing capacity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Maximum Borrowing Capacity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateEarlyAdoption_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in accounting principle, accounting standards update, early adoption [true false]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateEarlyAdoption_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change in Accounting Principle, Accounting Standards Update, Early Adoption [true false]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosure of Asset and Liability Not Measured at Fair Value [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Disclosure Of Asset And Liability Not Measured At Fair Value [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTaxAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss), Investment and Derivative, Operating, and Foreign Currency Transaction, after Tax [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTaxAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unrealized and Realized Gains (Losses):</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2025 Q3 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2025 Q3 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2025 Q3 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">First-lien Loan due 10/2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 2/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due October Two Thousand Twenty Eight.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Eight [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($68,775 par, Due 5/2024)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due May Two Thousand Twenty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueMayTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due May Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q3BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023 Q3 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q3BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023 Q3 base dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q3BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023 Q3 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdministrationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Administration agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdministrationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Administration Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdministrationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Administration Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MadisonParkCloSeriesTwoThousandEighteenTwentyEightAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Madison Park CLO, Series Two Thousand Eighteen Twenty Eight A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MadisonParkCloSeriesTwoThousandEighteenTwentyEightAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Madison Park CLO, series two thousand eighteen twenty eight A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SkylarkUkDebtcoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SkyLark UK DebtCo Limited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SkylarkUkDebtcoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Skylark Uk Debtco Limited [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SkylarkUkDebtcoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">SkyLark UK DebtCo Limited.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due April two thousand twenty five three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Five Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($17,412 par, due 4/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ModernHireIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Modern Hire, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ModernHireIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Modern Hire Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ModernHireIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Modern Hire, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BlackScholesModelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Black Scholes model.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BlackScholesModelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Black Scholes Model [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BlackScholesModelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Black Scholes Model</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FrontlineTechnologiesGroupLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Frontline technologies group, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FrontlineTechnologiesGroupLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Frontline Technologies Group L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FrontlineTechnologiesGroupLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Frontline Technologies Group, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MarketingServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Marketing Services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MarketingServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Marketing Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MarketingServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Marketing Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LetterOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Letter of Credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LetterOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Letter of Credit [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and Cash Equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGlobalMarketStrategiesCLOLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carlyle global market strategies CLO Ltd series two thousand eighteen one A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGlobalMarketStrategiesCLOLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Carlyle Global Market Strategies C L O Ltd Series Two Thousand Eighteen One A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGlobalMarketStrategiesCLOLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Carlyle Global Market Strategies CLO Ltd, Series 2018-1A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedGainOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Unrealized gain on investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedGainOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain On Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedGainOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross unrealized gain</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VitaBidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vita Bidco, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VitaBidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Vita Bidco, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VitaBidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Vita Bidco, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AmericanMoneyManagementCorpCloLtdSeriesTwoThousandSixteenEighteenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">American Money Management Corp CLO Ltd, Series 2016-18A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AmericanMoneyManagementCorpCloLtdSeriesTwoThousandSixteenEighteenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">American Money Management Corp CLO Ltd Series Two Thousand Sixteen Eighteen A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AmericanMoneyManagementCorpCloLtdSeriesTwoThousandSixteenEighteenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">American Money Management Corp CLO Ltd Series Two Thousand Sixteen-Eighteen A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility Maturity on February 4, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility Maturity on February 4, 2026 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving credit facility maturity on February 4, 2026,</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VelocityClinicalResearchIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Velocity Clinical Research, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VelocityClinicalResearchIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Velocity Clinical Research Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VelocityClinicalResearchIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Velocity clinical research inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="currency_AUD_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Australia, Dollars</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="currency_AUD_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">AUD</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Cash, Cash Equivalents, and Restricted Cash, End of Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Cash, cash equivalents, and restricted cash, beginning of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CedarFundingCloLtdSeriesTwoThousandEighteenSevenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cedar Funding CLO Ltd, Series 2018-7A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CedarFundingCloLtdSeriesTwoThousandEighteenSevenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cedar Funding Clo Ltd, Series Two Thousand Eighteen Seven A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CedarFundingCloLtdSeriesTwoThousandEighteenSevenAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cedar Funding Clo Ltd, Series 2018-7A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawAndRevolverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Delayed draw and revolver.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawAndRevolverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw And Revolver [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawAndRevolverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Delayed Draw &amp; Revolver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialCommitmentToInvesteeFutureAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Financial Support to Investee Contractually Required, Not Provided, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialCommitmentToInvesteeFutureAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Portfolio Company Commitments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Distributable Earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeisureProductsAndServicesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leisure Products and Services Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeisureProductsAndServicesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Leisure products and services sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeisureProductsAndServicesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leisure Products &amp; Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 9/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan Due September Two Thousand Twenty Six Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Six Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q3BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2024 Q3 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q3BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2024 Q3 base dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2024Q3BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q3 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentySixThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due June two thousand twenty six three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentySixThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due June Two Thousand Twenty Six Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentySixThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan($27,375par,due6/2026)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EmploymentHeroHoldingsPtyLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Employment Hero Holdings Pty Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EmploymentHeroHoldingsPtyLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employment Hero Holdings Pty Ltd [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EmploymentHeroHoldingsPtyLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employment Hero Holdings Pty Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleSeniorNotesDueTwentyTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Convertible Senior Notes Due Twenty Twenty Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleSeniorNotesDueTwentyTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Convertible Senior Notes Due Twenty Twenty Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleSeniorNotesDueTwentyTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Convertible Senior Notes Due 2022 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CapitalContributed_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Capital contributed</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CapitalContributed_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Capital Contributed</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CapitalContributed_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Capital contributed.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 1</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 1 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Stock [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class Of Stock [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Financing Activity, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Cash Provided by (Used in) Financing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Notes Payable, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Notes Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Outstanding Principal</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net change in unrealized gains (losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SummaryInvestmentHoldingsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Investment Holdings [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SummaryInvestmentHoldingsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Industry Composition of Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SummaryInvestmentHoldingsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Summary of Industry Composition of Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q4SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023 Q4 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q4SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023 Q4 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change in Accounting Principle, Accounting Standards Update, Adopted [true false]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment, par</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Face Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DyeDurhamCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dye &amp; Durham Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DyeDurhamCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dye &amp; Durham Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DyeDurhamCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dye Durham Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($47,999 par, Due 10/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due October Two Thousand Twenty Five One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Five One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SlBuyerCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">SL Buyer Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SlBuyerCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">SL Buyer Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SlBuyerCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SL Buyer Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Management Fee Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Management fees payable to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_FI_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finland</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_FI_lbl" xlink:role="http://www.xbrl.org/2003/role/label">FINLAND</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CoupaHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Coupa Holdings L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CoupaHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Coupa Holdings LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CoupaHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Coupa Holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AutoAftermarketAndServicesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Auto Aftermarket and Services Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AutoAftermarketAndServicesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Auto aftermarket and services sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AutoAftermarketAndServicesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Auto Aftermarket &amp; Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total investments at fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total investments at fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments, Fair Value Disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AlternativeInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AlternativeInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Alternative Investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nonoperating Income (Expense) [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sales Proceeds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeContractTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Contract [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeContractTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Contract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SignificantAccountingPoliciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Significant Accounting Policies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SignificantAccountingPoliciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Significant accounting policies.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndStructuredCreditInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity and Structured Credit Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndStructuredCreditInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity And Structured Credit Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndStructuredCreditInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity and structured credit investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BenefitStreetPartnersCloLtdSeriesTwoThousandFifteenBRMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Benefit Street Partners CLO Ltd, Series 2015-BR</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BenefitStreetPartnersCloLtdSeriesTwoThousandFifteenBRMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Benefit Street Partners Clo Ltd, Series Two Thousand Fifteen B R [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BenefitStreetPartnersCloLtdSeriesTwoThousandFifteenBRMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Benefit street partners Clo Ltd, Series 2015-BR.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiscalPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fiscal Year End</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiscalPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fiscal Period, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KyribaCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Kyriba Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KyribaCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Kyriba Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KyribaCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Kyriba Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonStockWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock Warrant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonStockWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonStockWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConsumerSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consumer Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConsumerSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consumer Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxAuthorityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Jurisdiction [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxAuthorityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Tax Authority</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VerdadResourcesIntermediateHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Verdad Resources Intermediate Holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VerdadResourcesIntermediateHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Verdad Resources Intermediate Holdings, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_VerdadResourcesIntermediateHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Verdad Resources Intermediate Holdings L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TelecommunicationsSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Telecommunications Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TelecommunicationsSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Telecommunications sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TelecommunicationsSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Telecommunications</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividends payable date of shares issued day month and year.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable Date Of Shares Issued Day Month And Year</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends date shares issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Securities Available For Sale [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Interactive Data Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Interactive Data Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty twenty four notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty Four Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Income Location, Balance [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WranglerTopcoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Wrangler TopCo, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WranglerTopcoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Wrangler TopCo, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WranglerTopcoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Wrangler Topco, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Flows from Operating Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 11/2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due November Two Thousand Twenty Seven.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due November Two Thousand Twenty Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accretion (Amortization) of Discounts and Premiums, Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net amortization of discount on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueMayTwoThousandTwentyEightOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Convertible note due may two thousand twenty eight one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueMayTwoThousandTwentyEightOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Convertible Note Due May Two Thousand Twenty Eight One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConvertibleNoteDueMayTwoThousandTwentyEightOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Convertible note ($4,124par,due5/2028)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HirevueIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hirevue, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HirevueIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hirevue, inc member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HirevueIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">HireVue, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienNoteDueMarchTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien note ($13,000 par, due 3/2029)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienNoteDueMarchTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First-lien Note Due March Two Thousand Twenty Nine [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienNoteDueMarchTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Note Due March Two Thousand Twenty Nine.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EnvironmentalIndustriesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Environmental Industries Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EnvironmentalIndustriesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Environmental industries sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EnvironmentalIndustriesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Environmental Industries</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AresCloLtdSeriesTwoThousandTwentyOneFiftyNineAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ares CLO Ltd, Series 2021-59A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AresCloLtdSeriesTwoThousandTwentyOneFiftyNineAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ares CLO Ltd Series Two Thousand Twenty One Fifty Nine A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AresCloLtdSeriesTwoThousandTwentyOneFiftyNineAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ares CLO Ltd Series Two Thousand Twenty One Fifty Nine A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q1BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023 Q1 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q1BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023 Q1 base dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2023Q1BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023 Q1 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q1BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2025 Q1 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q1BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2025 Q1 Base Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2025Q1BaseDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2025 Q1 base dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due august two thousand twenty five two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due August Two Thousand Twenty Five Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan ($64,435 par, due 8/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Tax Identification Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Tax Identification Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien revolving loan April two thousand twenty five three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan April Two Thousand Twenty Five Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien revolving loan (EUR 336 par, due 4/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueSeptemberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien loan (GBP 10,217 par, due 9/2028)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueSeptemberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan One Due September Two Thousand Twenty Eight [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanOneDueSeptemberTwoThousandTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan One Due September Two Thousand Twenty Eight.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ShareRepurchaseProgramApprovalDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Repurchase Program, Approval Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ShareRepurchaseProgramApprovalDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Share repurchase program, approval date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ShareRepurchaseProgramApprovalDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share repurchase program, approval date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MidoceanCreditCloLtdSeriesTwoThousandSixteenSixAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">MidOcean Credit CLO Ltd, Series Two Thousand Sixteen Six A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MidoceanCreditCloLtdSeriesTwoThousandSixteenSixAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">MidOcean Credit CLO Ltd, series two thousand sixteen six A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty twenty six notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty Six Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2026 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 10/2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Nine [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due october two thousand twenty nine.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Term Debt, Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MediaBroadcastingAndSubscriptionSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Media Broadcasting and Subscription Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MediaBroadcastingAndSubscriptionSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Media broadcasting and subscription sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MediaBroadcastingAndSubscriptionSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Media: Broadcasting &amp; Subscription</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net realized gains (losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AllegroCloLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Allegro CLO Ltd, Series 2018-1A</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AllegroCloLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Allegro CLO Ltd Series Two Thousand Eighteen One A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AllegroCloLtdSeriesTwoThousandEighteenOneAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Allegro CLO Ltd Series Two Thousand Eighteen One A.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Hedge, Investing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Local Phone Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Local Phone Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Transaction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PreferredUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PreferredUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Units [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PreferredUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Preferred units.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IntegratedPracticeSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Integrated Practice Solutions, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IntegratedPracticeSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Integrated Practice Solutions Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IntegratedPracticeSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Integrated Practice Solutions, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GrossInvestmentIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gross Investment Income, Operating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GrossInvestmentIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GrossInvestmentIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GrossInvestmentIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan due 4/2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due April Two Thousand Twenty Five One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Five One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WeightedAverageSpreadOnSeniorSecuredLoans_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Spread on Senior Secured Loans</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WeightedAverageSpreadOnSeniorSecuredLoans_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Weighted average spread on senior secured loans.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WeightedAverageSpreadOnSeniorSecuredLoans_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average spread on senior secured loans</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Payments of Financing Costs, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments of Financing Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EnergyOilAndGasSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Energy Oil and Gas Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EnergyOilAndGasSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Energy oil and gas sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EnergyOilAndGasSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Energy: Oil &amp; Gas</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassCOneUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Class C-1 Units.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassCOneUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class C One Units [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ClassCOneUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class C-1 Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingPoliciesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Policies [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2026Q1SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2026 Q1 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2026Q1SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2026 Q1 supplemental dividends member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_O2026Q1SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2026 Q1 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Shares issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, Dividend Reinvestment Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock issued in connection with dividend reinvestment plan, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperatingPaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Income, Operating, Paid in Kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperatingPaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Paid-in-kind interest income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperatingPaidInKind_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Paid-in-kind interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MetalsAndMiningSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Metals and Mining Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MetalsAndMiningSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Metals and mining sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MetalsAndMiningSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Metals &amp; Mining</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromInvestmentsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from investments, net.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromInvestmentsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Investments Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromInvestmentsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from investments, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LIHAHoldcoBVMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">LIHA Holdco B.V. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LIHAHoldcoBVMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">LIHA holdco B.V.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LIHAHoldcoBVMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">LIHA Holdco B.V.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ABL FILO Term Loan due 9/2022</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ABL FILO term loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ABLFILOTermLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">A B L F I L O Term Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyContractualFeeWaived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Contractual Fee Waived</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyContractualFeeWaived_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Investment Company, Contractual Fee Waived, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyContractualFeeWaived_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Management and incentive fees waived (Note 3)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Stock [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product due 7/2034</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due July Two Thousand Thirty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueJulyTwoThousandThirtyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due July Two Thousand Thirty Four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_AffiliatedEntityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Affiliated Entity [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_AffiliatedEntityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Affiliated Entity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfStockByClassTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock, Class of Stock [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfStockByClassTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Stock By Class [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Astra2LHoldingsIILLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Astra2 L Holdings I I L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Astra2LHoldingsIILLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Astra 2L Holdings II LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Astra2LHoldingsIILLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Astra 2L Holdings II LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">First-lien loan (AUD 17,400 par, due 12/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan (AUD 15,982 par, Due 12/2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MitnickTaAggregatorLpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Mitnick TA Aggregator, LP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MitnickTaAggregatorLpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Mitnick TA Aggregator, LP [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MitnickTaAggregatorLpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Mitnick TA aggregator, LP.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Emerging Growth Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Emerging Growth Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MediaAdvertisingPrintingAndPublishingSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Media Advertising, Printing and Publishing Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MediaAdvertisingPrintingAndPublishingSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Media advertising, printing and publishing Sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MediaAdvertisingPrintingAndPublishingSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Media: Advertising, Printing &amp; Publishing</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_SE_lbl" xlink:role="http://www.xbrl.org/2003/role/label">SWEDEN</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_SE_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sweden</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EuroInterbankOfferRateEURIBORMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Euro Interbank Offer Rate (EURIBOR) [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SterlingOvernightIndexAverageRateSONIAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sterling overnight index average rate (SONIA).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NorwegianInterbankOfferedRateNIBORMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Norwegian interbank offered rate (NIBOR).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NorwegianInterbankOfferedRateNIBORMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Norwegian Interbank Offered Rate (NIBOR) [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EuroInterbankOfferRateEURIBORMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Euro interbank offer rate (EURIBOR).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StockholmInterbankOfferedRateSTIBORMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Stockholm Interbank Offered Rate (STIBOR).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StockholmInterbankOfferedRateSTIBORMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholm Interbank Offered Rate (STIBOR) [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SterlingOvernightIndexAverageRateSONIAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sterling Overnight Index Average Rate (SONIA) [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent" xlink:to="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_O2024Q2SupplementalDividendsMember" xlink:to="tslx_O2024Q2SupplementalDividendsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapFourMember" xlink:to="tslx_InterestRateSwapFourMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_StructuredProductTwoMember" xlink:to="tslx_StructuredProductTwoMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromShortTermDebt" xlink:to="us-gaap_ProceedsFromShortTermDebt_lbl"/>
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  <xsd:element id="tslx_FirstLienLoanDueMarchTwoThousandTwentyFourMember" name="FirstLienLoanDueMarchTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SprinklrIncMember" name="SprinklrIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock" name="ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_DrydenSeniorLoanFundSeriesTwoThousandEighteenFiftyFiveAMember" name="DrydenSeniorLoanFundSeriesTwoThousandEighteenFiftyFiveAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AzuriteIntermediateHoldingsIncMember" name="AzuriteIntermediateHoldingsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductThreeMember" name="StructuredProductThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineMember" name="TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OtherIncomePolicyTextBlock" name="OtherIncomePolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_IncreaseDecreaseInInterestReceivablePaidInKind" name="IncreaseDecreaseInInterestReceivablePaidInKind" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveFourMember" name="FirstLienLoanDueAprilTwoThousandTwentyFiveFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAprilTwoThousandTwentySixOneMember" name="FirstLienLoanDueAprilTwoThousandTwentySixOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FrontlineTechnologiesGroupLLCMember" name="FrontlineTechnologiesGroupLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ElysianFincoLtdMember" name="ElysianFincoLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJulyTwoThousandTwentyTwoMember" name="FirstLienLoanDueJulyTwoThousandTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_HomecareSoftwareSolutionsLLCMember" name="HomecareSoftwareSolutionsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InternetServicesMember" name="InternetServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueJulyTwoThousandThirtyMember" name="StructuredProductDueJulyTwoThousandThirtyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyTwoMember" name="FirstLienLoanDueOctoberTwoThousandTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AdviserMember" name="AdviserMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EmploymentHeroHoldingsPtyLtdMember" name="EmploymentHeroHoldingsPtyLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PartnershipInterestOwnershipPercentage" name="PartnershipInterestOwnershipPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FirstLienLoanDueMayTwoThousandTwentyFourMember" name="FirstLienLoanDueMayTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MembershipInterestMember" name="MembershipInterestMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SubordinatedNoteMember" name="SubordinatedNoteMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_SkyBidcoSPAMember" name="SkyBidcoSPAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MindBodyIncMember" name="MindBodyIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ChemicalsPlasticsAndRubberSectorMember" name="ChemicalsPlasticsAndRubberSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CoupaHoldingsLLCMember" name="CoupaHoldingsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RetailAndConsumerProductsMember" name="RetailAndConsumerProductsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NewportParentHoldingsLPMember" name="NewportParentHoldingsLPMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2024Q4SupplementalDividendsMember" name="O2024Q4SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2023Q1SupplementalDividendsMember" name="O2023Q1SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJulyTwoThousandTwentySevenOneMember" name="FirstLienLoanDueJulyTwoThousandTwentySevenOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMarchTwoThousandTwentyNineMember" name="FirstLienLoanDueMarchTwoThousandTwentyNineMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RisksRelatedToEconomicConditionsMember" name="RisksRelatedToEconomicConditionsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ExtraHopNetworksIncMember" name="ExtraHopNetworksIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EnvironmentalIndustriesSectorMember" name="EnvironmentalIndustriesSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LineOfCreditFacilityExtendedDate" name="LineOfCreditFacilityExtendedDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_RisksRelatedToOurSecuritiesMember" name="RisksRelatedToOurSecuritiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyTwentySixNotesMember" name="TwentyTwentySixNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TangoManagementConsultingTwoMember" name="TangoManagementConsultingTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyOneMember" name="FirstLienLoanDueJanuaryTwoThousandTwentyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ClearCompanyLLCMember" name="ClearCompanyLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanParDueSeptemberTwoThousandTwentyOneMember" name="FirstLienLoanParDueSeptemberTwoThousandTwentyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ArtisanBidcoIncMember" name="ArtisanBidcoIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentAdvisoryAgreementMember" name="InvestmentAdvisoryAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember" name="CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixOneMember" name="FirstLienLoanDueDecemberTwoThousandTwentySixOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EquityAndOtherInvestmentsMember" name="EquityAndOtherInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_GcAgileHoldingsLtdMember" name="GcAgileHoldingsLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SixthStreetSpecialtyLendingIncMember" name="SixthStreetSpecialtyLendingIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NetAssetsDisclosureTextBlock" name="NetAssetsDisclosureTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveMember" name="FirstLienLoanDueOctoberTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_HumanResourceSupportServicesMember" name="HumanResourceSupportServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyTwentyNineNotesMember" name="TwentyTwentyNineNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixOneMember" name="FirstLienLoanDueSeptemberTwoThousandTwentySixOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MarcuraEquitiesLtdMember" name="MarcuraEquitiesLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember" name="RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BlackScholesModelMember" name="BlackScholesModelMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SeniorSecuredLoans" name="SeniorSecuredLoans" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_BswiftLlcMember" name="BswiftLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OrganizationPolicyTextBlock" name="OrganizationPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentyThreeOneMember" name="FirstLienLoanDueDecemberTwoThousandTwentyThreeOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BlueSnapIncMember" name="BlueSnapIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourOneMember" name="FirstLienLoanDueOctoberTwoThousandTwentyFourOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BenefitStreetPartnersCloLtdSeriesTwoThousandFifteenBRMember" name="BenefitStreetPartnersCloLtdSeriesTwoThousandFifteenBRMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAugustTwoThousandTwentyTwoMember" name="FirstLienLoanDueAugustTwoThousandTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ElysiumBidCoLimitedMember" name="ElysiumBidCoLimitedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyThreeTwoMember" name="FirstLienLoanDueSeptemberTwoThousandTwentyThreeTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_KangarooBidcoASMember" name="KangarooBidcoASMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_UnRealizedInvestmentGainsLossesAbstract" name="UnRealizedInvestmentGainsLossesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMayTwoThousandTwentyFourFourMember" name="FirstLienLoanDueMayTwoThousandTwentyFourFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" name="PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_MetalsAndMiningSectorMember" name="MetalsAndMiningSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredCreditPartnersJVLLCJointVentureInvestmentsMember" name="StructuredCreditPartnersJVLLCJointVentureInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OxfordSquareCapitalCorpMember" name="OxfordSquareCapitalCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_QuantrosIncMember" name="QuantrosIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DaySmartHoldingsLLCMember" name="DaySmartHoldingsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2024Q4BaseDividendsMember" name="O2024Q4BaseDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest" name="InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_LithiumTechnologiesLLCMember" name="LithiumTechnologiesLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentyTwoThreeMember" name="FirstLienLoanDueDecemberTwoThousandTwentyTwoThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAprilTwoThousandTwentySixMember" name="FirstLienLoanDueAprilTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IlluminateEducationIncMember" name="IlluminateEducationIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DyeDurhamLtdMember" name="DyeDurhamLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyThreeMember" name="FirstLienLoanDueOctoberTwoThousandTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapFourMember" name="InterestRateSwapFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio" name="MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_PrimeRevenueIncMember" name="PrimeRevenueIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PrimePayIntermediateLLCMember" name="PrimePayIntermediateLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CifcCloLimitedSeriesTwoThousandAndTwentyOneFourAMember" name="CifcCloLimitedSeriesTwoThousandAndTwentyOneFourAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EdgeBidcoBVMember" name="EdgeBidcoBVMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_UtilitiesOilAndGasSectorMember" name="UtilitiesOilAndGasSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock" name="ReimbursementOfTransactionRelatedExpensesPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_KasewareIntermediateHoldingCompanyMember" name="KasewareIntermediateHoldingCompanyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LynxBidcoMember" name="LynxBidcoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2024Q1BaseDividendsMember" name="O2024Q1BaseDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MotusLLCMember" name="MotusLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentsFairValueDisclosureNet" name="InvestmentsFairValueDisclosureNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_RevolvingCreditFacilityMaturityOnMarch42025Member" name="RevolvingCreditFacilityMaturityOnMarch42025Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LucidworksIncMember" name="LucidworksIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TradingScreenIncMember" name="TradingScreenIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AssetValuationWaterfallMember" name="AssetValuationWaterfallMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyTwentyFourNotesMember" name="TwentyTwentyFourNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved" name="PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_AVSCHoldingCorpMember" name="AVSCHoldingCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock" name="OffsettingAssetsAndLiabilitiesPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock" name="ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_HMPOmnimediaLLCMember" name="HMPOmnimediaLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_KryptonaBidCoUSLLCMember" name="KryptonaBidCoUSLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyTwentyThreeNotesMember" name="TwentyTwentyThreeNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienDebtInvestmentsMember" name="FirstLienDebtInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OmnigoSoftwareLLCMember" name="OmnigoSoftwareLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SixthStreetLendingPartnersMember" name="SixthStreetLendingPartnersMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ABLFILOTermLoanDueMayTwoThousandTwentySixMember" name="ABLFILOTermLoanDueMayTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CarlyleGroupMember" name="CarlyleGroupMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PenneyBorrowerLlcMember" name="PenneyBorrowerLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienTermLoanDueDecemberTwoThousandTwentySixMember" name="FirstLienTermLoanDueDecemberTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ManagementFeeWaiverHurdle" name="ManagementFeeWaiverHurdle" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_CrunchtimeInformationSystemsIncMember" name="CrunchtimeInformationSystemsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveFourMember" name="FirstLienLoanDueOctoberTwoThousandTwentyFiveFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyTwentyTwoConvertibleNotesMember" name="TwentyTwentyTwoConvertibleNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfNonQualifyingAssets" name="PercentageOfNonQualifyingAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_WhiteboxCloILtdSeriesTwoThousandTwentyTwoAMember" name="WhiteboxCloILtdSeriesTwoThousandTwentyTwoAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyFiveMember" name="FirstLienLoanDueSeptemberTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ValantMedicalSolutionsIncMember" name="ValantMedicalSolutionsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductOneMember" name="StructuredProductOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FinancialServicesMember" name="FinancialServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AvidXchangeIncMember" name="AvidXchangeIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveOneMember" name="FirstLienLoanDueAprilTwoThousandTwentyFiveOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductTwoMember" name="StructuredProductTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_GTreasurySSLLCMember" name="GTreasurySSLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EquityOwnershipVotingPercentage" name="EquityOwnershipVotingPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FirstLienLoanDueNovemberTwoThousandTwentySixTwoMember" name="FirstLienLoanDueNovemberTwoThousandTwentySixTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NortheastMember" name="NortheastMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TSImagineIncMember" name="TSImagineIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_HighTechIndustriesSectorMember" name="HighTechIndustriesSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NorwegianInterbankOfferedRateNIBORMember" name="NorwegianInterbankOfferedRateNIBORMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EquityInvestmentVariableInterestRateTypeExtensibleEnumeration" name="EquityInvestmentVariableInterestRateTypeExtensibleEnumeration" type="enum2:enumerationItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" enum2:domain="us-gaap:VariableRateDomain" enum2:headUsable="false" enum2:linkrole="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists"/>
  <xsd:element id="tslx_InterestRateSwapThreeMember" name="InterestRateSwapThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AssetCoveragePercentage" name="AssetCoveragePercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_CirrusBidcoLtdMember" name="CirrusBidcoLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AblFiloTermLoanDueAugustTwoThousandTwentySevenMember" name="AblFiloTermLoanDueAugustTwoThousandTwentySevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RisksRelatedToOurBusinessAndStructureMember" name="RisksRelatedToOurBusinessAndStructureMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CapitalContributed" name="CapitalContributed" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_OilGasAndConsumableFuelsMember" name="OilGasAndConsumableFuelsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueJuneTwoThousandThirtyOneMember" name="StructuredProductDueJuneTwoThousandThirtyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_GalileoParentincMember" name="GalileoParentincMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_JeffersonMillCloLtdSeriesTwoThousandFifteenOneAMember" name="JeffersonMillCloLtdSeriesTwoThousandFifteenOneAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyThreeOneMember" name="FirstLienLoanDueSeptemberTwoThousandTwentyThreeOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_JonasCollectionsAndRecoveryIncMember" name="JonasCollectionsAndRecoveryIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BearOpCoLLCMember" name="BearOpCoLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJuneTwoThousandTwentySixOneMember" name="FirstLienLoanDueJuneTwoThousandTwentySixOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2023Q3BaseDividendsMember" name="O2023Q3BaseDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AffiliatedMember" name="AffiliatedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InformationClearinghouseLLCAndMSMarketServiceLLCMember" name="InformationClearinghouseLLCAndMSMarketServiceLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJuneTwoThousandTwentyThreeMember" name="FirstLienLoanDueJuneTwoThousandTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2024Q3SupplementalDividendsMember" name="O2024Q3SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AsgIiLlcMember" name="AsgIiLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAprilTwoThousandTwentySevenOneMember" name="FirstLienLoanDueAprilTwoThousandTwentySevenOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueAprilTwoThousandThirtyFourMember" name="StructuredProductDueAprilTwoThousandThirtyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AresLoanFundingILtdSeriesTwoThousandTwentyOneAlfaClassEMember" name="AresLoanFundingILtdSeriesTwoThousandTwentyOneAlfaClassEMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate" name="PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveMember" name="FirstLienRevolvingLoanAprilTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PageUpPeopleLtdMember" name="PageUpPeopleLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentyOneMember" name="FirstLienLoanDueDecemberTwoThousandTwentyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ServiceChannelHoldingsIncMember" name="ServiceChannelHoldingsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RapidDataGmbhUnternehmensberatungMember" name="RapidDataGmbhUnternehmensberatungMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJuneTwoThousandTwentyTwoMember" name="FirstLienLoanDueJuneTwoThousandTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss" name="InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_FirstLienLoansDueDecemberTwoThousandTwentyFiveMember" name="FirstLienLoansDueDecemberTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ValidityIncMember" name="ValidityIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_VerdadResourcesIntermediateLLCMember" name="VerdadResourcesIntermediateLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ForestProductsAndPaperSectorMember" name="ForestProductsAndPaperSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SwapSettlement" name="SwapSettlement" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_AblFiloTermLoanDueDecemberTwoThousandTwentyFiveMember" name="AblFiloTermLoanDueDecemberTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BenNevisMidcoLimitedMember" name="BenNevisMidcoLimitedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ApteanIncMember" name="ApteanIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IbisIntermediateCoMember" name="IbisIntermediateCoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMayTwothousandTwentySixOneMember" name="FirstLienLoanDueMayTwothousandTwentySixOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SecondLienLoanDueOctoberTwoThousandTwentyNineOneMember" name="SecondLienLoanDueOctoberTwoThousandTwentyNineOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ClassAOneUnitsMember" name="ClassAOneUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CommonUnitsMember" name="CommonUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvmetricsHoldingsIncMember" name="InvmetricsHoldingsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductFourMember" name="StructuredProductFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees" name="IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_O2024Q2SupplementalDividendsMember" name="O2024Q2SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SapphireSoftwareBuyerIncMember" name="SapphireSoftwareBuyerIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAprilTwoThousandTwentyFourOneMember" name="FirstLienLoanDueAprilTwoThousandTwentyFourOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_KyribaCorpMember" name="KyribaCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2025Q3BaseDividendsMember" name="O2025Q3BaseDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueJulyTwoThousandThirtyFiveMember" name="StructuredProductDueJulyTwoThousandThirtyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SecuredBorrowings" name="SecuredBorrowings" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_AblFiloTermLoanOneDueAprilTwoThousandTwentyFourMember" name="AblFiloTermLoanOneDueAprilTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InsuranceMember" name="InsuranceMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ConvertibleNoteDueDecemberTwoThousandTwentyFourMember" name="ConvertibleNoteDueDecemberTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2023Q4BaseDividendsMember" name="O2023Q4BaseDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ConvertibleNoteDueSeptemberTwoThousandTwentyThreeMember" name="ConvertibleNoteDueSeptemberTwoThousandTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ProjectPIntermediate2LLCMember" name="ProjectPIntermediate2LLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OctagonInvestmentPartnersEighteenLimitedSeriesTwoThousandEighteenEighteenAMember" name="OctagonInvestmentPartnersEighteenLimitedSeriesTwoThousandEighteenEighteenAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_KkrCloLtdFortyNineAMember" name="KkrCloLtdFortyNineAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock" name="IncomeTaxesIncludingExciseTaxesPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_CordanceOperationsLlcMember" name="CordanceOperationsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CarlyleGlobalMarketStrategiesCLOLtdSeriesTwoThousandEighteenOneAMember" name="CarlyleGlobalMarketStrategiesCLOLtdSeriesTwoThousandEighteenOneAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AgreementTerminationPeriodWithoutPenalty" name="AgreementTerminationPeriodWithoutPenalty" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" name="PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_MitnickCorporatePurchaserIncMember" name="MitnickCorporatePurchaserIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RevolvingCreditsFacilitiesMember" name="RevolvingCreditsFacilitiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoansDueAugustTwoThousandTwentyFiveOneMember" name="FirstLienLoansDueAugustTwoThousandTwentyFiveOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentOwnedParValue" name="InvestmentOwnedParValue" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_ClassBUnitsMember" name="ClassBUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_GoldentreeCloLtdSeriesTwoThousandTwentySevenAMember" name="GoldentreeCloLtdSeriesTwoThousandTwentySevenAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EquityOwnershipCapitalCommitmentAmount" name="EquityOwnershipCapitalCommitmentAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets" name="PercentageOfManagementFeeCalculatedOnGrossAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FirstLienLoanDueAugustTwoThousandTwentyThreeMember" name="FirstLienLoanDueAugustTwoThousandTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyThreeMember" name="FirstLienLoanDueSeptemberTwoThousandTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ABLFirstLienLoanMember" name="ABLFirstLienLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NetwrixCorpMember" name="NetwrixCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BusinessServicesMember" name="BusinessServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourFourMember" name="FirstLienLoanDueOctoberTwoThousandTwentyFourFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ScorpioBidcoMember" name="ScorpioBidcoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanDecemberTwoThousandTwentySixMember" name="FirstLienRevolvingLoanDecemberTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EquityAndStructuredCreditInvestmentsMember" name="EquityAndStructuredCreditInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienTermLoanDueSeptemberTwoThousandTwentyFiveMember" name="FirstLienTermLoanDueSeptemberTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_IntelePeerHoldingsIncMember" name="IntelePeerHoldingsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJuneTwoThousandTwentyFiveMember" name="FirstLienLoanDueJuneTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncentiveFeesOnNetInvestmentIncome" name="IncentiveFeesOnNetInvestmentIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_TwoThousandTwentyFourSwapTransactionMember" name="TwoThousandTwentyFourSwapTransactionMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WestMember" name="WestMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EquityOfferingExpensesPolicyTextBlock" name="EquityOfferingExpensesPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_AfsTechnologiesIncMember" name="AfsTechnologiesIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienSecuredNoteDueJulyTwoThousandTwentyThreeMember" name="FirstLienSecuredNoteDueJulyTwoThousandTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CedarFundingCloLtdSeriesTwoThousandEighteenSevenAMember" name="CedarFundingCloLtdSeriesTwoThousandEighteenSevenAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJulyTwoThousandTwentyThreeMember" name="FirstLienLoanDueJulyTwoThousandTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJuneTwoThousandTwentyNineMember" name="FirstLienLoanDueJuneTwoThousandTwentyNineMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2024Q2BaseDividendsMember" name="O2024Q2BaseDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EquityInvestmentBasisSpreadVariableRate" name="EquityInvestmentBasisSpreadVariableRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_UnrealizedLossOnInvestments" name="UnrealizedLossOnInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanMember" name="FirstLienRevolvingLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_JointVentureInvestments" name="JointVentureInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_CommonSharesClassAMember" name="CommonSharesClassAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TrustCertificatesTwoMember" name="TrustCertificatesTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_GreenshootBidcoBVMember" name="GreenshootBidcoBVMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FairValueOfAnEffectiveHedge" name="FairValueOfAnEffectiveHedge" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_ArcwoodEnvironmentalIncMember" name="ArcwoodEnvironmentalIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DyeDurhamCorpMember" name="DyeDurhamCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BenefitStreetPartnersCloLtdSeriesTwoThousandFifteenEightAMember" name="BenefitStreetPartnersCloLtdSeriesTwoThousandFifteenEightAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EventusBuyerLLCMember" name="EventusBuyerLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenThreeMember" name="FirstLienLoanDueDecemberTwoThousandTwentySevenThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BctoBluebillBuyerIncMember" name="BctoBluebillBuyerIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJuneTwoThousandTwentySixTwoMember" name="FirstLienLoanDueJuneTwoThousandTwentySixTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ABLFILOTermLoanMember" name="ABLFILOTermLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueNovemberTwoThousandTwentyFiveMember" name="FirstLienLoanDueNovemberTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WorkwellAcquisitionCoMember" name="WorkwellAcquisitionCoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ClassAUnitsMember" name="ClassAUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MagnetiteCloLtdSeriesTwoThousandTwentyOneThirtyAMember" name="MagnetiteCloLtdSeriesTwoThousandTwentyOneThirtyAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ScheduleOfContributedCapitalAndUnfundedCommitmentsTableTextBlock" name="ScheduleOfContributedCapitalAndUnfundedCommitmentsTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwentyTwentyFiveMember" name="FirstLienLoanDueDecemberTwentyTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyNineNotesMember" name="TwoThousandTwentyNineNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ValuationTechniqueCostOfInvestmentsMember" name="ValuationTechniqueCostOfInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ReliaQuestHoldingsLLCMember" name="ReliaQuestHoldingsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SeriesAPreferredStockWarrantsMember" name="SeriesAPreferredStockWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PurchaseCommitmentToFundInvestment" name="PurchaseCommitmentToFundInvestment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_SeriesCTwoPreferredSharesMember" name="SeriesCTwoPreferredSharesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NumberOfPortfolioCompanies" name="NumberOfPortfolioCompanies" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_MidwestMember" name="MidwestMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentyTwoMember" name="FirstLienLoanDueDecemberTwoThousandTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanDueAprilTwoThousandTwentyFourMember" name="FirstLienRevolvingLoanDueAprilTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapFiveMember" name="InterestRateSwapFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StockIssuedDuringPeriodValueOfRemained" name="StockIssuedDuringPeriodValueOfRemained" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveThreeMember" name="FirstLienLoanDueAprilTwoThousandTwentyFiveThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueJanuaryTwoThousandThirtyMember" name="StructuredProductDueJanuaryTwoThousandThirtyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CarlyleGlobalMarketStrategiesCloLtdSeriesTwoThousandFourteenFourRaMember" name="CarlyleGlobalMarketStrategiesCloLtdSeriesTwoThousandFourteenFourRaMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanOctoberTwoThousandTwentyFiveMember" name="FirstLienRevolvingLoanOctoberTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_HigherLogicLLCMember" name="HigherLogicLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMayTwoThousandTwentyFourThreeMember" name="FirstLienLoanDueMayTwoThousandTwentyFourThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyTwentyEightNotesMember" name="TwentyTwentyEightNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_VarinemGermanBidcoGmbhMember" name="VarinemGermanBidcoGmbhMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveMember" name="FirstLienLoanDueAprilTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJulyTwoThousandTwentyEightMember" name="FirstLienLoanDueJulyTwoThousandTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PdiTaHoldingsIncMember" name="PdiTaHoldingsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMayTwoThousandTwentyFourTwoMember" name="FirstLienLoanDueMayTwoThousandTwentyFourTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BtrsHoldingsIncMember" name="BtrsHoldingsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAprilTwoThousandTwentyThreeOneMember" name="FirstLienLoanDueAprilTwoThousandTwentyThreeOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2025Q2SupplementalDividendsMember" name="O2025Q2SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LineOfCreditFacilityStatedMaturityDate" name="LineOfCreditFacilityStatedMaturityDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_OfficeProductsMember" name="OfficeProductsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueAprilTwoThousandThirtyOneMember" name="StructuredProductDueAprilTwoThousandThirtyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AstraAcquisitionCorpMember" name="AstraAcquisitionCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LeantaasHoldingsIncMember" name="LeantaasHoldingsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MidoceanCreditCloLtdSeriesTwoThousandSixteenSixAMember" name="MidoceanCreditCloLtdSeriesTwoThousandSixteenSixAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyEightMember" name="FirstLienLoanDueSeptemberTwoThousandTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ArrowheadPharmaceuticalsIncMember" name="ArrowheadPharmaceuticalsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanDueJanuaryTwoThousandTwentyFourMember" name="FirstLienRevolvingLoanDueJanuaryTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveTwoMember" name="FirstLienLoanDueOctoberTwoThousandTwentyFiveTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WeightedAverageSpreadOnSeniorSecuredLoans" name="WeightedAverageSpreadOnSeniorSecuredLoans" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_CarvalCloIiiLtdSeriesTwoThousandNineteenTwoAMember" name="CarvalCloIiiLtdSeriesTwoThousandNineteenTwoAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ReliaQuestLLCMember" name="ReliaQuestLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TangoManagementConsultingLLCMember" name="TangoManagementConsultingLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NmgParentLlcComUnitMember" name="NmgParentLlcComUnitMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SecondLienDebtInvestmentsMember" name="SecondLienDebtInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FactorSystemsIncMember" name="FactorSystemsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2024Q1SupplementalDividendsMember" name="O2024Q1SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMarchTwentyTwentyFourMember" name="FirstLienLoanDueMarchTwentyTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveOneMember" name="FirstLienLoanDueDecemberTwoThousandTwentyFiveOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_VitaTopcoIncMember" name="VitaTopcoIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IntegratedPracticeSolutionsIncMember" name="IntegratedPracticeSolutionsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss" name="InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_DrydenSeniorLoanFundSeriesTwoThousandTwentyEightySixAMember" name="DrydenSeniorLoanFundSeriesTwoThousandTwentyEightySixAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TIBCOSoftwareIncMember" name="TIBCOSoftwareIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueAprilTwoThousandThirtySixOneMember" name="StructuredProductDueAprilTwoThousandThirtySixOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OriginalIssueDiscountNetOfAccretion" name="OriginalIssueDiscountNetOfAccretion" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyFiveMember" name="FirstLienLoanDueJanuaryTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMarchTwentyTwentySixMember" name="FirstLienLoanDueMarchTwentyTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IRGSEHoldingCorpMember" name="IRGSEHoldingCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueJulyTwoThousandThirtyTwoMember" name="StructuredProductDueJulyTwoThousandThirtyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueNovemberTwoThousandTwentyNineMember" name="FirstLienLoanDueNovemberTwoThousandTwentyNineMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PreferredUnitsMember" name="PreferredUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LiabilitiesAndMembersEquityAbstract" name="LiabilitiesAndMembersEquityAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LegPurchaserIncMember" name="LegPurchaserIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAugustTwoThousandTwentyFiveMember" name="FirstLienLoanDueAugustTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MezzanineDebtInvestmentsMember" name="MezzanineDebtInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2026Q1BaseDividendsMember" name="O2026Q1BaseDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock" name="SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_AlaskaBidcoOyMember" name="AlaskaBidcoOyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentsInAndAdvancesToAffiliatesDividendIncome" name="InvestmentsInAndAdvancesToAffiliatesDividendIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_CommonSharesClassBMember" name="CommonSharesClassBMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DelayedDrawMember" name="DelayedDrawMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MDAmericaEnergyLLCMember" name="MDAmericaEnergyLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ConvertibleNotesDueJuneTwoThousandTwentySevenMember" name="ConvertibleNotesDueJuneTwoThousandTwentySevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueNovemberTwoThousandTwentyEightMember" name="FirstLienLoanDueNovemberTwoThousandTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CapitalEquipmentSectorMember" name="CapitalEquipmentSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DividendsPolicyTextBlock" name="DividendsPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_SMATechnologiesHoldingsLLCMember" name="SMATechnologiesHoldingsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests" name="PercentageOfNetProceedsOfSaleOfEquityInterests" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_TaxExpensePertainingToNetRealizedGainsRelatedToInvestments" name="TaxExpensePertainingToNetRealizedGainsRelatedToInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_LeverageWaiverMember" name="LeverageWaiverMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ManufacturingMember" name="ManufacturingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAugustTwoThousandTwentyTwoOneMember" name="FirstLienLoanDueAugustTwoThousandTwentyTwoOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienNoteOneDueJuneTwoThousandTwentyFourMember" name="FirstLienNoteOneDueJuneTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved" name="PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_RevolvingCreditFacilityMaturityOnApril232027Member" name="RevolvingCreditFacilityMaturityOnApril232027Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TelecommunicationsSectorMember" name="TelecommunicationsSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanJulyTwoThousandTwentyTwoMember" name="FirstLienRevolvingLoanJulyTwoThousandTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RailAcquisitionsLLCMember" name="RailAcquisitionsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanMember" name="FirstLienLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EMSLinqIncMember" name="EMSLinqIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions" name="NetRealizedGainsLossesOnForeignCurrencyTransactions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_CopperBidcoLLCMember" name="CopperBidcoLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SeriesAPreferredUnitsMember" name="SeriesAPreferredUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_VoyaCloLtdSeries20183AMember" name="VoyaCloLtdSeries20183AMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OutsystemsLuxcoMember" name="OutsystemsLuxcoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_USRParentIncMember" name="USRParentIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJuneTwoThousandTwentySixThreeMember" name="FirstLienLoanDueJuneTwoThousandTwentySixThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AblFiloTermLoanDueMayTwoThousandTwentyFourMember" name="AblFiloTermLoanDueMayTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentySixTwoMember" name="FirstLienLoanDueOctoberTwoThousandTwentySixTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees" name="PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate" name="PercentageOfCapitalGainsFromApril12024HurdleRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_Octagon57LlcSeries20211AMember" name="Octagon57LlcSeries20211AMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_GeneralRiskFactorsMember" name="GeneralRiskFactorsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC" name="MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_ConvertibleSeniorNotesDueTwentyNineteenMember" name="ConvertibleSeniorNotesDueTwentyNineteenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyEightMember" name="FirstLienLoanDueJanuaryTwoThousandTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SummaryOfGeographicCompositionOfJointVentureInvestmentsPortfolioAtFairValueTableTextBlock" name="SummaryOfGeographicCompositionOfJointVentureInvestmentsPortfolioAtFairValueTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandTwentyTwoMember" name="FirstLienRevolvingLoanDueOctoberTwoThousandTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MediaBroadcastingAndSubscriptionSectorMember" name="MediaBroadcastingAndSubscriptionSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AlphaMidcoIncMember" name="AlphaMidcoIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMayTwoThousandTwentySixMember" name="FirstLienLoanDueMayTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DividendsDeclaredDuringThePeriod" name="DividendsDeclaredDuringThePeriod" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentySixMember" name="FirstLienLoanDueOctoberTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanMayTwoThousandTwentyFourMember" name="FirstLienRevolvingLoanMayTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwaps" name="InterestRateSwaps" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandTwentyEightOneMember" name="FirstLienRevolvingLoanDueOctoberTwoThousandTwentyEightOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DeferredTaxAssetsPertainingToNetUnrealizedGainsRelatedToInvestments" name="DeferredTaxAssetsPertainingToNetUnrealizedGainsRelatedToInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member" name="RevolvingCreditFacilityMaturityOnFebruary42026Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BabylonFincoLimitedMember" name="BabylonFincoLimitedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FullsteamOperationsLlcMember" name="FullsteamOperationsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EDBParentLLCMember" name="EDBParentLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_KahuaIncMember" name="KahuaIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CurrentMarketPricePerSharePercentage" name="CurrentMarketPricePerSharePercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_SubordinatedNoteDueSeptemberTwoThousandTwentySixMember" name="SubordinatedNoteDueSeptemberTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ConvertibleNoteMember" name="ConvertibleNoteMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees" name="ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixFourMember" name="FirstLienLoanDueSeptemberTwoThousandTwentySixFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MurchisonOilAndGasLlcMember" name="MurchisonOilAndGasLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoansDueDecemberTwoThousandTwentyFourMember" name="FirstLienLoansDueDecemberTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ShareRepurchaseProgramApprovalDate" name="ShareRepurchaseProgramApprovalDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_WeightedAverageYieldOnSeniorSecuredLoansAtFairValue" name="WeightedAverageYieldOnSeniorSecuredLoansAtFairValue" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FirstLienLoanDueMayTwoThousandTwentyFourOneMember" name="FirstLienLoanDueMayTwoThousandTwentyFourOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ConvertibleNoteDueMayTwoThousandTwentyEightOneMember" name="ConvertibleNoteDueMayTwoThousandTwentyEightOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_JointVentureInvestmentsMember" name="JointVentureInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_HeritageEnvironmentalServicesIncMember" name="HeritageEnvironmentalServicesIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MississippiResourcesLLCMember" name="MississippiResourcesLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NondeductibleFederalExciseTaxPercentage" name="NondeductibleFederalExciseTaxPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_Rule10B51ArrModifiedFlag" name="Rule10B51ArrModifiedFlag" type="xbrli:booleanItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_MauricesIncMember" name="MauricesIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ModernHireIncMember" name="ModernHireIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SlBuyerCorpMember" name="SlBuyerCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_UtilitiesElectricSectorMember" name="UtilitiesElectricSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_VitaBidcoIncMember" name="VitaBidcoIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RevolverAndEquityMember" name="RevolverAndEquityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock" name="SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_NinetyNineCentsOnlyStoresLLCMember" name="NinetyNineCentsOnlyStoresLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ElectronicsMember" name="ElectronicsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SterlingOvernightIndexAverageRateSONIAMember" name="SterlingOvernightIndexAverageRateSONIAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear" name="DividendsPayableDateOfSharesIssuedDayMonthAndYear" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly" name="PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_HotelGamingAndLeisureMember" name="HotelGamingAndLeisureMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ShiftmoveGmbhMember" name="ShiftmoveGmbhMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DelayedDrawAndRevolverMember" name="DelayedDrawAndRevolverMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixTwoMember" name="FirstLienLoanDueDecemberTwoThousandTwentySixTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanJuneTwoThousandTwentyTwoMember" name="FirstLienRevolvingLoanJuneTwoThousandTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAprilTwoThousandTwentyThreeMember" name="FirstLienLoanDueAprilTwoThousandTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanParDueSeptemberTwoThousandTwentyOneMember" name="FirstLienRevolvingLoanParDueSeptemberTwoThousandTwentyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WindRiverCloLtdSeriesTwoThousandEighteenThreeAMember" name="WindRiverCloLtdSeriesTwoThousandEighteenThreeAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueFebruaryTwoThousandTwentySevenMember" name="FirstLienLoanDueFebruaryTwoThousandTwentySevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StockholmInterbankOfferedRateSTIBORMember" name="StockholmInterbankOfferedRateSTIBORMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RisksRelatedToOurPortfolioCompanyInvestmentsMember" name="RisksRelatedToOurPortfolioCompanyInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AcceoSolutionsIncMember" name="AcceoSolutionsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanOneDueJulyTwoThousandTwentyFourMember" name="FirstLienLoanOneDueJulyTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAprilTwoThousandTwentySevenMember" name="FirstLienLoanDueAprilTwoThousandTwentySevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ParkAvenueInstitutionalAdvisersCloLtdSeriesTwoThousandEighteenOneAMember" name="ParkAvenueInstitutionalAdvisersCloLtdSeriesTwoThousandEighteenOneAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RaptorUsBuyerIiCorpMember" name="RaptorUsBuyerIiCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFourMember" name="FirstLienLoanDueDecemberTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AblFirstLienLoanDueAugustTwoThousandTwentyFiveMember" name="AblFirstLienLoanDueAugustTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenMember" name="FirstLienLoanDueDecemberTwoThousandTwentySevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly" name="PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_RainFocusLLCMember" name="RainFocusLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EquityInvestmentsMember" name="EquityInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TruckLiteCoLlcMember" name="TruckLiteCoLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CommunicationsMember" name="CommunicationsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfInvestmentsAtFairValue" name="PercentageOfInvestmentsAtFairValue" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_MerativeLPMember" name="MerativeLPMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ApellisPharmaceuticalsIncMember" name="ApellisPharmaceuticalsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes" name="NetExpenseForFederalExciseTaxAndOtherTaxes" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_ABLFILOTermLoanDueMayTwoThousandTwentyFiveMember" name="ABLFILOTermLoanDueMayTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ShackeltonCloLtdSeries20157RaMember" name="ShackeltonCloLtdSeries20157RaMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJuneTwoThousandTwentySixMember" name="FirstLienLoanDueJuneTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BtrsHoldingIncMember" name="BtrsHoldingIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WarrantTwoMember" name="WarrantTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AllegroCloLtdSeriesTwoThousandEighteenOneAMember" name="AllegroCloLtdSeriesTwoThousandEighteenOneAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveThreeMember" name="FirstLienLoanDueOctoberTwoThousandTwentyFiveThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienNoteDueJuneTwoThousandTwentyFourMember" name="FirstLienNoteDueJuneTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MadisonParkCloSeriesTwoThousandEighteenTwentyEightAMember" name="MadisonParkCloSeriesTwoThousandEighteenTwentyEightAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CarlyleGlobalMarketStrategiesCLOLtdSeriesTwoThousandSeventeenFourAMember" name="CarlyleGlobalMarketStrategiesCLOLtdSeriesTwoThousandSeventeenFourAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LeisureProductsAndServicesSectorMember" name="LeisureProductsAndServicesSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CommonStockWarrantsMember" name="CommonStockWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ConsumerGoodsDurableSectorMember" name="ConsumerGoodsDurableSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AmericanMoneyManagementCorpCloLtdSeriesTwoThousandSixteenEighteenAMember" name="AmericanMoneyManagementCorpCloLtdSeriesTwoThousandSixteenEighteenAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AerospaceAndDefenseSectorMember" name="AerospaceAndDefenseSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MDAmericaEnergyLimitedLiabilityCompanyMember" name="MDAmericaEnergyLimitedLiabilityCompanyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SeriesCOnePreferredSharesMember" name="SeriesCOnePreferredSharesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter" name="PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_VelocityClinicalResearchIncMember" name="VelocityClinicalResearchIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SouthMember" name="SouthMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BigWombatHoldingIncMember" name="BigWombatHoldingIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SecondLienLoanDueOctoberTwoThousandTwentyNineMember" name="SecondLienLoanDueOctoberTwoThousandTwentyNineMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EquityDistributionAgreementMember" name="EquityDistributionAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_JCPenneyCompanyIncMember" name="JCPenneyCompanyIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ProceedsFromInvestmentsNet" name="ProceedsFromInvestmentsNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_FirstLienLoanDueJulyTwoThousandTwentyFiveMember" name="FirstLienLoanDueJulyTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanDueJanuaryTwoThousandAndTwentyFourMember" name="FirstLienRevolvingLoanDueJanuaryTwoThousandAndTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RevolvingCreditFacilityMaturityOnApril242029Member" name="RevolvingCreditFacilityMaturityOnApril242029Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AdministrationAgreementMember" name="AdministrationAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_GulfStreamMeridianSeriesTwoThousandTwentyOneSixAMember" name="GulfStreamMeridianSeriesTwoThousandTwentyOneSixAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IngenovisHealthFinanceLLCMember" name="IngenovisHealthFinanceLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly" name="PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_O2024Q3BaseDividendsMember" name="O2024Q3BaseDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_GulfStreamMeridianSeriesTwoThousandTwentyOneFourAMember" name="GulfStreamMeridianSeriesTwoThousandTwentyOneFourAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OtherMember" name="OtherMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IbisUSBlockerCoMember" name="IbisUSBlockerCoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WeightedAverageYieldOnPrincipalAmountOfOutstandingDebtInvestments" name="WeightedAverageYieldOnPrincipalAmountOfOutstandingDebtInvestments" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_MeritSoftwareFinanceHoldingsLlcMember" name="MeritSoftwareFinanceHoldingsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentyEightMember" name="FirstLienLoanDueDecemberTwoThousandTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentDueDate" name="InvestmentDueDate" type="xbrli:gYearMonthItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_HornetsecurityHoldingGmbhMember" name="HornetsecurityHoldingGmbhMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2025Q1BaseDividendsMember" name="O2025Q1BaseDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_UnfundedCommitments" name="UnfundedCommitments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_EuroInterbankOfferRateEURIBORMember" name="EuroInterbankOfferRateEURIBORMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ClassATwoUnitsMember" name="ClassATwoUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanDueAugustTwoThousandTwentyThreeMember" name="FirstLienRevolvingLoanDueAugustTwoThousandTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentIncomeOther" name="InvestmentIncomeOther" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_InvestmentsOwnedEstimatedCostBasis" name="InvestmentsOwnedEstimatedCostBasis" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_NonRule10B51ArrModifiedFlag" name="NonRule10B51ArrModifiedFlag" type="xbrli:booleanItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_PharmaceuticalsMember" name="PharmaceuticalsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ChemicalsMember" name="ChemicalsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RMCFIVCIVXXXVLPMember" name="RMCFIVCIVXXXVLPMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_HirevueIncMember" name="HirevueIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredCreditMember" name="StructuredCreditMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome" name="InvestmentsInAndAdvancesToAffiliatesOtherIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_HippoXpaBidcoAbMember" name="HippoXpaBidcoAbMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock" name="InterestAndDividendIncomeRecognitionPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_TwoThousandTwentyFourTwentySixTwentyEightTwentyNineAndTwentyThirtyNotesMember" name="TwoThousandTwentyFourTwentySixTwentyEightTwentyNineAndTwentyThirtyNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OtherInvestmentMember" name="OtherInvestmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueOctoberTwoThousandThirtyFourMember" name="StructuredProductDueOctoberTwoThousandThirtyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount" name="FairValueOfSecuritiesAsPercentageOfNetAssetsAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_IntegrationApplianceIncMember" name="IntegrationApplianceIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyNineMember" name="FirstLienLoanDueSeptemberTwoThousandTwentyNineMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WholesaleSectorMember" name="WholesaleSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAugustTwoThousandTwentySixOneMember" name="FirstLienLoanDueAugustTwoThousandTwentySixOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SignificantAccountingPoliciesTable" name="SignificantAccountingPoliciesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2025Q3SupplementalDividendsMember" name="O2025Q3SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WranglerTopcoLlcMember" name="WranglerTopcoLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfIncentiveFeeRate" name="PercentageOfIncentiveFeeRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanOctoberTwoThousandTwentyFourMember" name="FirstLienRevolvingLoanOctoberTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanOneDueMarchTwoThousandTwentyFourMember" name="FirstLienLoanOneDueMarchTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandThirtyNotesMember" name="TwoThousandThirtyNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveOneMember" name="FirstLienRevolvingLoanAprilTwoThousandTwentyFiveOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2025Q1SupplementalDividendsMember" name="O2025Q1SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SignalPeakCloLLCSeriesTwoThousandEighteenFiveAMember" name="SignalPeakCloLLCSeriesTwoThousandEighteenFiveAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CifcCloLtdSeriesTwoThousandEighteenThreeAMember" name="CifcCloLtdSeriesTwoThousandEighteenThreeAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DividendsTextBlock" name="DividendsTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_TwentyThirtyNotesMember" name="TwentyThirtyNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RevolvingCreditFacilityMaturityOnMay12026Member" name="RevolvingCreditFacilityMaturityOnMay12026Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueJulyTwoThousandThirtyThreeMember" name="StructuredProductDueJulyTwoThousandThirtyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyEightNotesMember" name="TwoThousandTwentyEightNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ChangeInFairValueOfAnEffectiveHedge" name="ChangeInFairValueOfAnEffectiveHedge" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_DesignerBrandsIncMember" name="DesignerBrandsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CrewlineBuyerIncMember" name="CrewlineBuyerIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanDueMayTwoThousandTwentyFourMember" name="FirstLienRevolvingLoanDueMayTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJanuaryTwoThousandTwentyFourMember" name="FirstLienLoanDueJanuaryTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WindRiverCloLtdSeries20142AMember" name="WindRiverCloLtdSeries20142AMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ABLFILOTermLoanDueAprilTwoThousandTwentyFourMember" name="ABLFILOTermLoanDueAprilTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJuneTwoThousandTwentyEightMember" name="FirstLienLoanDueJuneTwoThousandTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CeltraTechnologiesIncMember" name="CeltraTechnologiesIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ConvertibleNoteDueMayTwoThousandTwentyEightMember" name="ConvertibleNoteDueMayTwoThousandTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PikesPeakCloSeriesTwoThousandTwentyOneNineAMember" name="PikesPeakCloSeriesTwoThousandTwentyOneNineAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixSevenMember" name="FirstLienLoanDueSeptemberTwoThousandTwentySixSevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OrganizationAndBasisOfPresentationLineItems" name="OrganizationAndBasisOfPresentationLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TotalReturnBasedOnMarketValue" name="TotalReturnBasedOnMarketValue" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_DestinySolutionsParentHoldingCompanyMember" name="DestinySolutionsParentHoldingCompanyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFourOneMember" name="FirstLienLoanDueDecemberTwoThousandTwentyFourOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductsMember" name="StructuredProductsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJulyTwoThousandTwentyFourMember" name="FirstLienLoanDueJulyTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFiveOneMember" name="FirstLienLoanDueOctoberTwoThousandTwentyFiveOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MitnickTaAggregatorLpMember" name="MitnickTaAggregatorLpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_VerdadResourcesIntermediateHoldingsLLCMember" name="VerdadResourcesIntermediateHoldingsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SummaryOfIndustryCompositionOfJointVentureInvestmentsPortfolioAtFairValueTableTextBlock" name="SummaryOfIndustryCompositionOfJointVentureInvestmentsPortfolioAtFairValueTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_Astra2LHoldingsIILLCMember" name="Astra2LHoldingsIILLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MidoceanCreditCloLtdSeries20189AMember" name="MidoceanCreditCloLtdSeries20189AMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixMember" name="FirstLienLoanDueDecemberTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LIHAHoldcoBVMember" name="LIHAHoldcoBVMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ConstructionAndBuildingSectorMember" name="ConstructionAndBuildingSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TransportationConsumerSectorMember" name="TransportationConsumerSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RevolverMember" name="RevolverMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OctagonInvestmentPartnersThirtyEightLtdSeriesTwoThousandEighteenOneAMember" name="OctagonInvestmentPartnersThirtyEightLtdSeriesTwoThousandEighteenOneAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BanyanSoftwareHoldingsLlcMember" name="BanyanSoftwareHoldingsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixFourMember" name="FirstLienLoanDueDecemberTwoThousandTwentySixFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock" name="ScheduleOfComponentsOfInterestExpenseTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_SeriesAaPreferredStockWarrantsMember" name="SeriesAaPreferredStockWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyNineMember" name="FirstLienLoanDueOctoberTwoThousandTwentyNineMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PayScaleHoldingsIncMember" name="PayScaleHoldingsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SkylarkUkDebtcoLimitedMember" name="SkylarkUkDebtcoLimitedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MediaDiversifiedAndProductionSectorMember" name="MediaDiversifiedAndProductionSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncentiveFeesOnNetCapitalGains" name="IncentiveFeesOnNetCapitalGains" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_FirstLienNoteDueMarchTwoThousandTwentyNineMember" name="FirstLienNoteDueMarchTwoThousandTwentyNineMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueNovemberTwoThousandTwentySixMember" name="FirstLienLoanDueNovemberTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AcousticLPMember" name="AcousticLPMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixMember" name="FirstLienLoanDueSeptemberTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome" name="InvestmentsInAndAdvancesToAffiliatesInterestIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_SouthwickParkCloLtdSeries20194AMember" name="SouthwickParkCloLtdSeries20194AMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MadisonParkFundingLtdSeriesTwoThousandFourteenFourteenAMember" name="MadisonParkFundingLtdSeriesTwoThousandFourteenFourteenAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MarketingServicesMember" name="MarketingServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SportAllianceGmbhMember" name="SportAllianceGmbhMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SignificantAccountingPoliciesLineItems" name="SignificantAccountingPoliciesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredCreditInvestments" name="StructuredCreditInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_FirstLienLoanDueMayTwoThousandTwentyNineMember" name="FirstLienLoanDueMayTwoThousandTwentyNineMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2023Q3SupplementalDividendsMember" name="O2023Q3SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMayTwoThousandTwentyEightMember" name="FirstLienLoanDueMayTwoThousandTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WeightedAverageYieldOnSeniorSecuredLoansAtAmortizedCost" name="WeightedAverageYieldOnSeniorSecuredLoansAtAmortizedCost" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_OzlmLtdSeriesTwoThousandEighteenEighteenAMember" name="OzlmLtdSeriesTwoThousandEighteenEighteenAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CarisLifeSciencesIncMember" name="CarisLifeSciencesIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ClassCOneUnitsMember" name="ClassCOneUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueAprilTwoThousandThirtyThreeMember" name="StructuredProductDueAprilTwoThousandThirtyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StewartParkCloLtdSeriesTwoThousandFifteenOneAMember" name="StewartParkCloLtdSeriesTwoThousandFifteenOneAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OrganizationAndBasisOfPresentationTable" name="OrganizationAndBasisOfPresentationTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ABLFILOTermLoanDueAprilTwoThousandTwentySevenMember" name="ABLFILOTermLoanDueAprilTwoThousandTwentySevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PayleaseLlcMember" name="PayleaseLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SecondLienLoanDueJuneTwoThousandTwentyFiveMember" name="SecondLienLoanDueJuneTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EatonCloLtdSeriesTwoThousandTwentyOneAMember" name="EatonCloLtdSeriesTwoThousandTwentyOneAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage" name="FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveMember" name="FirstLienLoanDueDecemberTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJulyTwoThousandTwentyFiveOneMember" name="FirstLienLoanDueJulyTwoThousandTwentyFiveOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanOneDueDecemberTwoThousandTwentyFiveMember" name="FirstLienLoanOneDueDecemberTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyThreeNotesMember" name="TwoThousandTwentyThreeNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WindRiverCloLtdSeriesTwoThousandSeventeenOneAMember" name="WindRiverCloLtdSeriesTwoThousandSeventeenOneAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredCreditInvestmentsMember" name="StructuredCreditInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductMember" name="StructuredProductMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EnergyOilAndGasSectorMember" name="EnergyOilAndGasSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2023Q4SupplementalDividendsMember" name="O2023Q4SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandAndTwentySevenMember" name="FirstLienRevolvingLoanDueOctoberTwoThousandAndTwentySevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyTwoConvertibleNotesMember" name="TwoThousandTwentyTwoConvertibleNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AresCloLtdSeriesTwoThousandTwentyOneFiftyNineAMember" name="AresCloLtdSeriesTwoThousandTwentyOneFiftyNineAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AutomotiveMember" name="AutomotiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PassportLabsIncMember" name="PassportLabsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ConvertibleSeniorNotesDueTwentyTwentyTwoMember" name="ConvertibleSeniorNotesDueTwentyTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueJulyTwoThousandThirtyOneMember" name="StructuredProductDueJulyTwoThousandThirtyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourMember" name="FirstLienLoanDueOctoberTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixTwoMember" name="FirstLienLoanDueSeptemberTwoThousandTwentySixTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueTransfers" name="InvestmentsInAndAdvancesToAffiliatesAtFairValueTransfers" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_AvalaraIncMember" name="AvalaraIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueFebruaryTwoThousandTwentyFourMember" name="FirstLienLoanDueFebruaryTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AmericanAchievementCorpMember" name="AmericanAchievementCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueFebruaryTwoThousandTwentySixMember" name="FirstLienLoanDueFebruaryTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NintexGlobalLtdMember" name="NintexGlobalLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_UsaDebuskLlcMember" name="UsaDebuskLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentyThreeMember" name="FirstLienLoanDueDecemberTwoThousandTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NonControlledAffiliatedInvestmentsMember" name="NonControlledAffiliatedInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved" name="PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_BCTOAcePurchaserIncMember" name="BCTOAcePurchaserIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueAprilTwoThousandThirtySixMember" name="StructuredProductDueAprilTwoThousandThirtySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyNineteenConvertibleNotesMember" name="TwentyNineteenConvertibleNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2023Q2SupplementalDividendsMember" name="O2023Q2SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AblFiloTermLoanDueSeptemberTwoThousandTwentyTwoMember" name="AblFiloTermLoanDueSeptemberTwoThousandTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AutoAftermarketAndServicesSectorMember" name="AutoAftermarketAndServicesSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2023Q1BaseDividendsMember" name="O2023Q1BaseDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ForeScoutTechnologiesIncMember" name="ForeScoutTechnologiesIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ArrowbuyerIncMember" name="ArrowbuyerIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2026Q1SupplementalDividendsMember" name="O2026Q1SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SediverSPAMember" name="SediverSPAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMarchTwoThousandTwentySixMember" name="FirstLienLoanDueMarchTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMayTwoThousandTwentyEightOneMember" name="FirstLienLoanDueMayTwoThousandTwentyEightOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueJanuaryTwoThousandThirtySevenMember" name="StructuredProductDueJanuaryTwoThousandThirtySevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanOneDueOctoberTwoThousandTwentyTwoMember" name="FirstLienLoanOneDueOctoberTwoThousandTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StockOfferingValueSharesAuthorizedToBeSold" name="StockOfferingValueSharesAuthorizedToBeSold" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember" name="FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RRLtdSeriesTwoThousandTwentyEightAMember" name="RRLtdSeriesTwoThousandTwentyEightAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_UnrealizedGainOnInvestments" name="UnrealizedGainOnInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_GainLossFormAdjustmentOfPaidInKindInterest" name="GainLossFormAdjustmentOfPaidInKindInterest" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_BayshoreIntermediate2LPMember" name="BayshoreIntermediate2LPMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EatonCloLtdSeriesTwoThousandFifteenOneAMember" name="EatonCloLtdSeriesTwoThousandFifteenOneAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TrustCertificatesOneMember" name="TrustCertificatesOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets" name="PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_EducationMember" name="EducationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueJulyTwentyTwentyFourMember" name="FirstLienLoanDueJulyTwentyTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ClinicientIncMember" name="ClinicientIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_QSRAcquisitionCoMember" name="QSRAcquisitionCoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueJulyTwoThousandThirtyFourMember" name="StructuredProductDueJulyTwoThousandThirtyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TRPAssetsLLCMember" name="TRPAssetsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FlightIntermediateHoldCoIncMember" name="FlightIntermediateHoldCoIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CarlyleSecuredLendingIncMember" name="CarlyleSecuredLendingIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ResmanLlcMember" name="ResmanLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueSeptemberTwoThousandTwentyTwoMember" name="FirstLienLoanDueSeptemberTwoThousandTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ConvertibleNoteDueMayTwoThousandTwentyFiveMember" name="ConvertibleNoteDueMayTwoThousandTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SMPAHoldingsLLCMember" name="SMPAHoldingsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveTwoMember" name="FirstLienRevolvingLoanAprilTwoThousandTwentyFiveTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueOctoberTwoThousandThirtyOneMember" name="StructuredProductDueOctoberTwoThousandThirtyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" name="PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_MediaAdvertisingPrintingAndPublishingSectorMember" name="MediaAdvertisingPrintingAndPublishingSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentySixTwentyEightTwentyNineAndTwentyThirtyNotesMember" name="TwoThousandTwentySixTwentyEightTwentyNineAndTwentyThirtyNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAprilTwoThousandTwentyFourMember" name="FirstLienLoanDueAprilTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RiskonnectIncMember" name="RiskonnectIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BainCapitalCreditCLOLtdSeriesTwoThousandEighteenOneAMember" name="BainCapitalCreditCLOLtdSeriesTwoThousandEighteenOneAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BedBathAndBeyondIncMember" name="BedBathAndBeyondIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NmgHoldingCompanyIncMember" name="NmgHoldingCompanyIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfLoansAtFloatingInterestRates" name="PercentageOfLoansAtFloatingInterestRates" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_CarlstarGroupLLCMember" name="CarlstarGroupLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LexipolLlcMember" name="LexipolLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredCreditPartnersJVLLCMember" name="StructuredCreditPartnersJVLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyEightMember" name="FirstLienLoanDueOctoberTwoThousandTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ConsumerGoodsNon-DurableSectorMember" name="ConsumerGoodsNon-DurableSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveThreeMember" name="FirstLienRevolvingLoanAprilTwoThousandTwentyFiveThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PingIdentityHoldingCorporationMember" name="PingIdentityHoldingCorporationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanOneDueSeptemberTwoThousandTwentyEightMember" name="FirstLienLoanOneDueSeptemberTwoThousandTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveTwoMember" name="FirstLienLoanDueDecemberTwoThousandTwentyFiveTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapOneMember" name="InterestRateSwapOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome" name="PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FolletCorpMember" name="FolletCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_Project44IncMember" name="Project44IncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CarlyleCreditSolutionsIncMember" name="CarlyleCreditSolutionsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueMayTwoThousandThirtyOneMember" name="StructuredProductDueMayTwoThousandThirtyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WideOrbitIncMember" name="WideOrbitIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixThreeMember" name="FirstLienLoanDueDecemberTwoThousandTwentySixThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SeverinAcquisitionLLCMember" name="SeverinAcquisitionLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueNovemberTwoThousandTwentySevenMember" name="FirstLienLoanDueNovemberTwoThousandTwentySevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NeuintelLLCMember" name="NeuintelLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ErlingLuxBidcoSarlMember" name="ErlingLuxBidcoSarlMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WarrantOneMember" name="WarrantOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMayTwoThousandTwentySevenOneMember" name="FirstLienLoanDueMayTwoThousandTwentySevenOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenOneMember" name="FirstLienLoanDueDecemberTwoThousandTwentySevenOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AledadeIncMember" name="AledadeIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TransportationMember" name="TransportationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapSixMember" name="InterestRateSwapSixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyFourNotesMember" name="TwoThousandTwentyFourNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AblDipTermLoanDueAprilTwoThousandTwentyOneMember" name="AblDipTermLoanDueAprilTwoThousandTwentyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember" name="RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentySixNotesMember" name="TwoThousandTwentySixNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueMayTwoThousandTwentyFourFiveMember" name="FirstLienLoanDueMayTwoThousandTwentyFourFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourThreeMember" name="FirstLienLoanDueOctoberTwoThousandTwentyFourThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PianoSoftwareIncMember" name="PianoSoftwareIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DiscoParentIncMember" name="DiscoParentIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_O2025Q2BaseDividendsMember" name="O2025Q2BaseDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets" name="PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FirstLienRevolvingLoanJuneTwoThousandTwentyThreeMember" name="FirstLienRevolvingLoanJuneTwoThousandTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AbsorbSoftwareIncMember" name="AbsorbSoftwareIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EquityStructuredCreditAndJointVentureInvestmentsMember" name="EquityStructuredCreditAndJointVentureInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TherapeuticsMDIncMember" name="TherapeuticsMDIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredProductDueJanuaryTwoThousandThirtyOneMember" name="StructuredProductDueJanuaryTwoThousandThirtyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BiohavenPharmaceuticalsIncMember" name="BiohavenPharmaceuticalsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ContainerPackagingAndGlassSectorMember" name="ContainerPackagingAndGlassSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienLoanDueAugustTwoThousandTwentySixMember" name="FirstLienLoanDueAugustTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
</xsd:schema>
