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<!-- DFIN New ActiveDisclosure (SM) XBRL Linkbase Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date :2023-02-16T15:35:18.7836+00:00 -->
<!-- Copyright (c) 2023 Donnelly Financial Solutions, Inc. All Rights Reserved. -->
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    <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 Level1 [Member]</link:label>
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    <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_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="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>
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    <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="us-gaap_DomesticCountryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Domestic Country [Member]</link:label>
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    <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>
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    <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>
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    <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>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionOriginalDebtAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Value of debt converted</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueJuneTwoThousandTwentyTwoOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due June Two Thousand Twenty Two One [Member]</link:label>
    <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="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="tslx_DerivativeInterestRateSwapPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative Interest rate swap paid.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeInterestRateSwapPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Interest Rate Swap Paid</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeInterestRateSwapPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Company Pays</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>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanAprilTwoThousandTwentyFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Revolving Loan April Two Thousand Twenty Five.</link:label>
    <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_DerivativeAssetNotionalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Notional Amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeAssetNotionalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Notional Amount Asset</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Convertible Notes Payable, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Convertible Notes Payable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate principal amount of notes surrendered for conversion</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="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="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="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 At Cost</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromSettlementsOfInterestRateSwapsRelatedToConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from settlements of interest rate swaps related to convertible notes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromSettlementsOfInterestRateSwapsRelatedToConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Settlements of Interest Rate Swaps Related to Convertible Notes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromSettlementsOfInterestRateSwapsRelatedToConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from Settlements of Interest Rate Swaps Related to Convertible Notes</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="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_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax liability pertaining to unrealized gains on investment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Liability Pertaining to Unrealized Gains Related to Investments</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred tax liability pertaining to unrealized gains related to investments.</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="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="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="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="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="dei_DocumentQuarterlyReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Quarterly Report</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">Debt Instrument [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="us-gaap_PaymentsForRepurchaseOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchases of treasury stock</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRepurchaseOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments for Repurchase of Common Stock</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="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share 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="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_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="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="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change In Accounting Principle Accounting Standards Update Immaterial Effect</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="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="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="us-gaap_LondonInterbankOfferedRateLIBORMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">LIBOR</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LondonInterbankOfferedRateLIBORMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">London Interbank Offered Rate L I B O R [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LondonInterbankOfferedRateLIBORMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">London Interbank Offered Rate (LIBOR)</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_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="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="us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, convertible, threshold percentage of stock price trigger</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger</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="us-gaap_AutomotiveSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Automotive</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AutomotiveSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Automotive Sector [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net realized gain (loss) on investments and foreign currency transactions</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_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="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Realized Gains Losses on Investments and Foreign Currency Translation</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net realized gains losses on investments and foreign currency translation.</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="us-gaap_IncomeTaxAuthorityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Authority [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_FirstLienLoanDueDecemberTwoThousandTwentySevenTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Seven Two.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Seven Two [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySevenTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($39,300 par, Due 12/2027)</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="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_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="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandTwentyFourMember_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_FirstLienRevolvingLoanDueOctoberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan Due October Two Thousand Twenty Four [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanDueOctoberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien revolving loan due october two thousand twenty four.</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="us-gaap_DebtPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt 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_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_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_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="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cumulative Effect, Period of Adoption, Adjustment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cumulative Effect, Period of Adoption, Adjustment [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/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="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="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="tslx_DerivativeAssetInterestRateSwapTenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative asset interest rate swap ten.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapTenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Interest Rate Swap Ten [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapTenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Asset Interest Rate Swap Ten</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_BaseDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Base dividend.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BaseDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Base Dividend [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BaseDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Base</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 Stockholders 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_TreasuryStockAcquiredAverageCostPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average price per share</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockAcquiredAverageCostPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock Acquired, Average Cost Per Share</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_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="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixThreeMember_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_FirstLienLoanDueSeptemberTwoThousandTwentySixThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Loan Due September Two Thousand Twenty Six Three.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueSeptemberTwoThousandTwentySixThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due September Two Thousand Twenty Six Three [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/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="us-gaap_ScheduleOfDerivativeInstrumentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Derivative Instruments [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="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="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_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_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_ManagementAndIncentiveFeeWaived_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="tslx_ManagementAndIncentiveFeeWaived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Management and Incentive Fee Waived</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementAndIncentiveFeeWaived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Management and incentive fee waived.</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_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="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_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_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="tslx_SpecialDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Special dividend.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SpecialDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Special Dividend [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SpecialDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Special</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_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_StructuredProductDueAprilTwoThousandThirtyOneOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due April two thousand thirty one one.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyOneOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due April Two Thousand Thirty One One [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyOneOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product Due April Two Thousand Thirty One One</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdjustmentForInterestExpenseAndDeferredFinancingCostsIncentiveFeeAndExciseTaxNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustment for interest expense and deferred financing costs on 2022 Convertible Notes, incentive fee and excise tax, net</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdjustmentForInterestExpenseAndDeferredFinancingCostsIncentiveFeeAndExciseTaxNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Adjustment for interest expense and deferred financing costs incentive fee and excise tax net.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdjustmentForInterestExpenseAndDeferredFinancingCostsIncentiveFeeAndExciseTaxNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustment For Interest Expense And Deferred Financing Costs Incentive Fee And Excise Tax Net</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_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale Of Stock Name Of Transaction [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_NumberOfConsecutiveBusinessDay_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of consecutive business days</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NumberOfConsecutiveBusinessDay_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Consecutive Business Day</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NumberOfConsecutiveBusinessDay_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of consecutive business day.</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="us-gaap_OperatingLossCarryforwards_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating loss carry forward generating tax refund</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLossCarryforwards_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Loss Carryforwards</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="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="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_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_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Expense, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest</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="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_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">Investment Company Realized And Unrealized Gain Loss On Investment And Foreign Currency</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_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_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_RevolvingCreditFacilityMaturityOnJanuary312025Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility Maturity on January 31, 2025</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility Maturity on January 31, 2025 [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving credit facility maturity on January 31, 2025.</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="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="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="us-gaap_TreasuryStockShares_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Treasury Stock, Shares, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock Shares</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockShares_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="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="tslx_IncreaseDecreaseInAdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase (decrease) in additional paid in capital</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInAdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease in Additional Paid in Capital</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInAdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in additional paid in capital.</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="srt_CumulativeEffectPeriodOfAdoptionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cumulative Effect, Period of Adoption [Axis]</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="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="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="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_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_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="us-gaap_InvestmentSecondaryCategorizationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Secondary Categorization [Axis]</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_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_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="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="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="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="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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">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="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_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="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in incentive fees on net capital gains accrued to affiliate.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Incentive Fees On Net Capital Gains Accrued To Affiliate</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate_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_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_InvestmentTypeCategorizationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Type Categorization [Member]</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_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_DebtInstrumentConvertibleBusinessDayPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument, convertible, business day period.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtInstrumentConvertibleBusinessDayPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, convertible, business day period</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtInstrumentConvertibleBusinessDayPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Convertible, Business Day Period</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="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_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_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_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_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_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="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_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="us-gaap_InvestmentCompanyRedemptionFeePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Repurchase of common stock</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyRedemptionFeePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Redemption Fee, Per Share</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="us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustment for dilutive effect of 2022 Convertible Notes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incremental Common Shares Attributable To Conversion Of Debt Securities</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">Issuance of common stock, net of offering costs</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="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="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_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_PaymentForRepurchasesOfDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Repurchases of debt</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaymentForRepurchasesOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payment For Repurchases Of Debt</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaymentForRepurchasesOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payment for repurchases Of debt.</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="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_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_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="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="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_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="us-gaap_NoninterestExpenseDirectorsFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Noninterest Expense Directors Fees</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="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="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_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="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_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_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="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">Available For Sale Debt Securities Amortized Cost Basis</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_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="us-gaap_DebtConversionConvertedInstrumentSharesIssued1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Conversion Converted Instrument Shares Issued1</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionConvertedInstrumentSharesIssued1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt conversion, shares Issued</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 Day Month And Year</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="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Range [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_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_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_CanadianDollarOfferedRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">CDOR</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CanadianDollarOfferedRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Canadian Dollar Offered Rate [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CanadianDollarOfferedRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Canadian Dollar Offered Rate.</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.</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 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_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_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_AssetCoveragePercentageAfterBorrowing_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset coverage percentage after borrowing</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetCoveragePercentageAfterBorrowing_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Coverage Percentage After Borrowing</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetCoveragePercentageAfterBorrowing_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Asset coverage percentage after borrowing.</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 Party Transactions By Related Party [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_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="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_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="tslx_EarningsPerShareBasicAndDilutedLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Earnings per share basic and diluted line items.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EarningsPerShareBasicAndDilutedLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share Basic And Diluted [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EarningsPerShareBasicAndDilutedLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings Per Share Basic And Diluted [Line Items]</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="us-gaap_DerivativeContractTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Contract Type [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="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="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock issued upon conversion of convertible notes, shares</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, Conversion of Convertible Securities</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="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_FirstLienLoanDueDecemberTwoThousandTwentySixFiveMember_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_FirstLienLoanDueDecemberTwoThousandTwentySixFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Six Five [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien loan due december two thousand twenty six five.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyNetAssetsFromOperationsIncreaseDecrease_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_InvestmentCompanyNetAssetsFromOperationsIncreaseDecrease_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Increase in Net Assets Resulting from Operations</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyNetAssetsFromOperationsIncreaseDecrease_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase in net assets resulting from operations</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyNetAssetsFromOperationsIncreaseDecrease_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Net Assets From Operations Increase Decrease</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_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="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&#8212;diluted</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_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="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_Dividends_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="us-gaap_Dividends_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Dividends, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Dividends_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends</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="srt_PartnershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Partnership Interest [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_PartnershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Partnership Interest</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 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="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="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="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_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="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="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="us-gaap_EarningsPerShareBasicAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share Basic [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasicAbstract_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="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="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_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">Stock Repurchase Program, Period in Force</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="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">Trading Securities Debt</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="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="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="tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of tax basis components of distributable earnings</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Tax Basis Components Of Distributable Earnings [Table Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of tax basis components of distributable earnings.</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_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock Value</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_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_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_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="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="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_InvestmentIncomeInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income Interest</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeInterest_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="us-gaap_InvestmentIncomeInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Interest Income</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="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="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_OtherNonoperatingIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Nonoperating Income</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncome_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_OtherNonoperatingIncome_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_DerivativeAssetInterestRateSwapOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative asset interest rate swap one.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Interest Rate Swap One [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Asset Interest Rate Swap One</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">Net Cash Provided By Used In Financing Activities</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="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_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction Selling General And Administrative Expenses From Transactions With Related Party</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty_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="tslx_DerivativeInterestRateSwapReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative Interest rate swap received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeInterestRateSwapReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Interest Rate Swap Received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeInterestRateSwapReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Company Receives</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="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="tslx_DerivativeAssetInterestRateSwapTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative asset interest rate swap two.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Interest Rate Swap Two [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Asset Interest Rate Swap Two</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapSevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative asset interest rate swap seven.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapSevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Interest Rate Swap Seven [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapSevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Asset Interest Rate Swap Seven</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/label">Investment Owned At 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/terseLabel">Total investments at fair value</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_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="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="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="srt_ScenarioUnspecifiedDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scenario Unspecified [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_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_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_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="tslx_FirstLienRevolvingLoanOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">First-lien Revolving Loan ($1,320 par, Due 10/2024)</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First Lien Revolving Loan October Two Thousand Twenty Two.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan October Two Thousand Twenty Two [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanOctoberTwoThousandTwentyTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Revolving Loan ($1,320 par, Due 10/2022)</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="us-gaap_ValuationTechniqueDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation 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_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="tslx_TaxReclassificationOfStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax reclassification of stockholders' equity in accordance with GAAP</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxReclassificationOfStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tax reclassification of stockholders' equity.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxReclassificationOfStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Reclassification Of Stockholders Equity</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtConversionPrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt conversion principal amount.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtConversionPrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Conversion Principal Amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtConversionPrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt conversion principal amount</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="srt_SegmentGeographicalDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment 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="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Range [Member]</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_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="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_PercentageOfCoveredDebtAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of covered debt</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfCoveredDebtAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Covered Debt Amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfCoveredDebtAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of covered debt amount.</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_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_SubsidiarySaleOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsidiary 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_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_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="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_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_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_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_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="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="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="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="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="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="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="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/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/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/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/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="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Cash proceeds from issuance of common stock, net of underwriting fees and offering 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/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="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="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="us-gaap_LongtermDebtTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Longterm Debt Type [Axis]</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_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 For Period 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_PaymentsForSettlementsOfInterestRateSwapsRelatedToConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payments for settlements of interest rate swaps related to convertible notes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaymentsForSettlementsOfInterestRateSwapsRelatedToConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments for Settlements of Interest Rate Swaps Related to Convertible Notes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaymentsForSettlementsOfInterestRateSwapsRelatedToConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payments for settlements of interest rate swaps related to convertible notes.</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">E U R</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="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="us-gaap_RatioOfIndebtednessToNetCapital1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ratio Of Indebtedness To Net Capital1</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_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="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="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="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="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 Of Derivative 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_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_AccountingStandardsUpdateExtensibleList_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Standards Update Extensible List</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingStandardsUpdateExtensibleList_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounting Standards Update [Extensible Enumeration]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetUnrealizedGainsLossesOnInvestments_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="tslx_NetUnrealizedGainsLossesOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Unrealized Gains (Losses) on Investments</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetUnrealizedGainsLossesOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net unrealized gains (losses) on investments.</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="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_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="tslx_DebtInstrumentInitialConversionRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, initial conversion rate</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtInstrumentInitialConversionRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Initial Conversion Rate</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtInstrumentInitialConversionRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument, initial conversion rate.</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="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="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_DerivativeNotionalAmountHeldDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Notional Amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeNotionalAmountHeldDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Notional Amount Held during Period</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeNotionalAmountHeldDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative notional amount held during period.</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>
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    <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_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="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="tslx_OtherTemporaryDifferences_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other temporary differences</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherTemporaryDifferences_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other temporary differences</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherTemporaryDifferences_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Temporary Differences</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherTemporaryDifferences_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other temporary differences.</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_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_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_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">Nondesignated [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_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number Of Diluted Shares Outstanding</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&#8212;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/totalLabel">Denominator for diluted weighted average shares</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>
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    <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_DerivativeLiabilityCollateralRightToReclaimCashOffset_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Liability 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="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="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="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_InvestmentReferenceRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Reference Rate</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentReferenceRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment reference rate.</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="tslx_TaxableIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Taxable Income</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxableIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Taxable Income</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxableIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Taxable income.</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_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="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_EquitySecuritiesFvNiCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity investment</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/label">Equity Securities, FV-NI</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/totalLabel">Equity Securities, FV-NI, Total</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_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="us-gaap_EquitySecuritiesByIndustryAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Securities By Industry [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_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_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="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="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 Maturity Dates</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">Transfers And Servicing Of Financial Instruments Types Of 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_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="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="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 Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations</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_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="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="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="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="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_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive fees on net investment income payable to affiliate.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fees On Net Investment Income Payable To Affiliate</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate_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_DerivativeAssetInterestRateSwapFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative asset interest rate swap five</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Interest Rate Swap Five [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Asset Interest Rate Swap Five</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_QuarterlyFinancialInformationDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Quarterly Financial Information Disclosure [Abstract]</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 [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_DerivativeLiabilitiesInterestRateSwapThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative liabilities interest rate swap three.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeLiabilitiesInterestRateSwapThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Liabilities Interest Rate Swap Three [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeLiabilitiesInterestRateSwapThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Liabilities Interest Rate Swap Three</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UndistributedNetInvestmentIncomeTaxBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Undistributed net investment income - tax basis</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UndistributedNetInvestmentIncomeTaxBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Undistributed Net Investment Income - Tax Basis</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UndistributedNetInvestmentIncomeTaxBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Undistributed net investment income - tax basis.</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="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_InvestmentPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment 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_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_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="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="tslx_NumberOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of investment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NumberOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Investments</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NumberOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of investments.</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="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Taxable Income</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Expense Benefit</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_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_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_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_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_DerivativeAssetInterestRateSwapSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative asset interest rate swap six.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Interest Rate Swap Six [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Asset Interest Rate Swap Six</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrdinaryIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ordinary Income</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrdinaryIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ordinary Income</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrdinaryIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ordinary income.</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/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="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Text Block]</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="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 Earnings1</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="us-gaap_IncomeTaxDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Abstract]</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="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="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="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="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</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="tslx_DerivativeAssetInterestRateSwapThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative asset interest rate swap three.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Interest Rate Swap Three [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Asset Interest Rate Swap Three</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="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="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned Percent 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/terseLabel">Percentage of Net Assets</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="tslx_DerivativeLiabilitiesInterestRateSwapOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative liabilities interest rate swap one.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeLiabilitiesInterestRateSwapOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Liabilities Interest Rate Swap One [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeLiabilitiesInterestRateSwapOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Liabilities Interest Rate Swap One</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/label">Net Asset Value Per Share</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/terseLabel">Net Asset Value Per Share</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-controlled, non-affiliated investments.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non Controlled Non Affiliated Investments [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember_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="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($46,624 par, Due 10/2024)</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due October Two Thousand Twenty Four two.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentyFourTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Four Two [Member]</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="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value By Fair Value Hierarchy Level [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="tslx_PercentageOfAdjustedBorrowingBaseUnderCreditFacility_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of adjusted borrowing base under credit facility</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAdjustedBorrowingBaseUnderCreditFacility_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Adjusted Borrowing Base Under Credit Facility</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAdjustedBorrowingBaseUnderCreditFacility_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of adjusted borrowing base under credit facility.</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="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="us-gaap_ConversionOfStockAmountConverted1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock issued in settlement of convertible notes during the period</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConversionOfStockAmountConverted1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Conversion of Stock, Amount Converted</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="us-gaap_EquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Abstract]</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="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/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/documentation">Investments fair value disclosure net.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in incentive fees on net investment income payable to affiliate.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Incentive Fees On Net Investment Income Payable To Affiliate</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate_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="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_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_RelatedPartyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party [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="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_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_BCTOAcePurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">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/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="srt_StatementScenarioAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement 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_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="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="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="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="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_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>
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    <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="tslx_FirstLienLoanDueDecemberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan (AUD 40,000 par, Due 12/2026)</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Industry Composition Of Investments At Fair Value Table [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock_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_ChangeInAccountingPrincipleAccountingStandardsUpdateEarlyAdoption_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change In Accounting Principle Accounting Standards Update Early Adoption</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="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="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_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="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="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="tslx_BainCapitalCreditCLOLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Bain Capital Credit CLO Ltd.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BainCapitalCreditCLOLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Bain Capital Credit C L O Ltd [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BainCapitalCreditCLOLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Bain Capital Credit C L O Ltd</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_NetExpenseForFederalExciseTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net expense for federal excise tax</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpenseForFederalExciseTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Expense For Federal Excise Tax</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpenseForFederalExciseTax_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net expense for federal excise tax.</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="us-gaap_PrimeRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prime Rate</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrimeRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prime Rate [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="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="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="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Repurchase of common stock</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Issuance And Repurchase Per Share</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company issuance and repurchase per share.</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">Stockholders' Equity Note Disclosure [Text Block]</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="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="us-gaap_EarningsPerShareDilutedAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share Diluted [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDilutedAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings per common share&#8212;diluted</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">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/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/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/totalLabel">Total Net Assets</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="us-gaap_InvestmentIncomeNet_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_InvestmentIncomeNet_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_InvestmentIncomeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Undistributed net investment income - tax basis</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Net</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EuroInterbankOfferRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">EIBOR</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EuroInterbankOfferRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Euro Interbank Offer Rate [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EuroInterbankOfferRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Euro Interbank Offer Rate.</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="us-gaap_IncomeApproachValuationTechniqueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Approach Valuation Technique [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="tslx_DividendDeclaredFromRealizedGainsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend declared from realized gains</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendDeclaredFromRealizedGainsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividend Declared From Realized Gains Per Share</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendDeclaredFromRealizedGainsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividend declared from realized gains per share.</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="tslx_UndistributedNetRealizedGainsLossesTaxBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Undistributed net realized gains (losses) - tax basis</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UndistributedNetRealizedGainsLossesTaxBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Undistributed net realized gains (losses) tax basis.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentsIncorporatedByReferenceTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Documents Incorporated by Reference</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_SterlingOvernightInterbankAverageRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SONIA</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SterlingOvernightInterbankAverageRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sterling Overnight Interbank Average Rate [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SterlingOvernightInterbankAverageRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sterling Overnight Interbank Average Rate.</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">Income Statement Location [Axis]</link:label>
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    <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</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_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="srt_CumulativeEffectPeriodOfAdoptionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cumulative Effect, Period of Adoption [Domain]</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="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_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement 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_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_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="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/terseLabel">Change in Unrealized Gains / (Losses)</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="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="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="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_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_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_CashAndCashEquivalentsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash And Cash Equivalents 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_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/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/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="us-gaap_ShortMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Company Receives</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShortMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Short [Member]</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="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_TwentyTwentyThreeNotesMember_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_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="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_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="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="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="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="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="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="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="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="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="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 Day Month And Year</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="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="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_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="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="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_DividendsDeclaredFromNetInvestmentIncomePerShare_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="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividends Declared From Net Investment Income Per Share.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Declared From Net Investment Income Per Share</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">Schedule Of Stock By Class [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="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="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="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_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="us-gaap_RepaymentsOfConvertibleDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Settlement of convertible notes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfConvertibleDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Repayments of Convertible Debt</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/terseLabel">2022 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/verboseLabel">Convertible Senior Notes Due 2022 [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/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="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="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="tslx_CommonStockIssuedInSettlementOfConvertibleNotesDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock issued in settlement of convertible notes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonStockIssuedInSettlementOfConvertibleNotesDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Issued In Settlement Of Convertible Notes During The Period</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonStockIssuedInSettlementOfConvertibleNotesDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock issued in settlement of convertible notes during the period.</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="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="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_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="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="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_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="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_NonoperatingIncomeExpense_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_NonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nonoperating Income Expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpense_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="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="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="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="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="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_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_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="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_DebtInstrumentConvertibleMeasurementPeriodConsecutiveTradingDays_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, convertible, measurement period, consecutive trading days</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtInstrumentConvertibleMeasurementPeriodConsecutiveTradingDays_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Convertible, Measurement Period, Consecutive Trading Days</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtInstrumentConvertibleMeasurementPeriodConsecutiveTradingDays_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument, convertible, measurement period, consecutive trading days.</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="us-gaap_AmortizationOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amortization Of Financing 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_IncreaseDecreaseInDistributableEarnings_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase (decrease) in distributable earnings</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInDistributableEarnings_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease in Distributable Earnings</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInDistributableEarnings_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in distributable earnings.</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="tslx_NetExpense_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_NetExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net Expense.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpense_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="srt_WeightedAverageMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Member</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="us-gaap_DebtInstrumentConvertibleThresholdTradingDays_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, convertible, threshold trading days</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdTradingDays_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Convertible, Threshold Trading Days</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_LongMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Company Pays</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValue_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_InvestmentsInAndAdvancesToAffiliatesAtFairValue_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_InvestmentsInAndAdvancesToAffiliatesAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, at Fair Value</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 Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [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_InterestRateSwapTenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap ten.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Ten [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Ten</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_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_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_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_SupplementalDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Supplemental dividend.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SupplementalDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Dividend [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SupplementalDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental</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_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="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty three and twenty four and twenty six notes.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Three And Twenty Four And Twenty Six Notes [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023 Notes, 2024 Notes and 2026 Notes</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 Date1</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="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="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_ComparablemultipleMember_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_ComparablemultipleMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ComparableMultiple[Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ComparablemultipleMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Comparable Multiple Member</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="tslx_SpecialDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Special</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SpecialDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Special Dividend Two [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SpecialDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Special Dividend Two.</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 Assets And Liabilities Measured On Recurring And Nonrecurring Basis 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 Significant Unobservable Inputs Used in Valuations</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="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="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="tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of reconciliation increase in net assets</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Reconciliation Increase In Net Assets [Table Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of reconciliation increase in net assets.</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 $15,437 and $14,399 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/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 Equivalents At Carrying Value</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Realized And Unrealized Gain Loss On Investment And Foreign Currency [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract_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="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_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="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="us-gaap_StatementClassOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement Class Of Stock [Axis]</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_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="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_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_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_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_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="us-gaap_MarketApproachValuationTechniqueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Market Approach Valuation Technique [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_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_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="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="tslx_InterestRateSwapTwelveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap twelve.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTwelveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Twelve [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTwelveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Twelve</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="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="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="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="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="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_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="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_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="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="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Operating Activities [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_InterestRateSwapEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap eight.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Eight [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Eight</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_DerivativeAssetInterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative asset interest rate swap.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Interest Rate Swap [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Asset Interest Rate Swap</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_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_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="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>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtInstrumentCovenantMinimumConsolidatedAssetsLessSecuredDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument, covenant, minimum consolidated assets net of secured debt.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtInstrumentCovenantMinimumConsolidatedAssetsLessSecuredDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Covenant, Minimum Consolidated Assets Less Secured Debt</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_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="srt_StatementGeographicalAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement 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="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_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_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 Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect</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="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Paid Net</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_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_InvestmentCompanySettlementOfConvertibleNotesPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Settlement of 2022 Convertible Notes</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company settlement of convertible notes per share</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="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="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_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="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="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_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of ordinary income qualified as interest related dividend exempt from US withholding tax applicable to non-US shareholder</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Ordinary Income Qualified as Interest Related Dividend Exempt from Domestic Withholding Tax Applicable to Foreign Shareholder</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of ordinary income qualified as interest related dividend exempt from domestic withholding tax applicable to foreign shareholder.</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/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="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="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_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="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financing Receivable Recorded Investment By 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="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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">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="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="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Assets Measured On Recurring Basis Change In 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_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="tslx_SecondLienLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Second lien loan.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Second Lien Loan [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Second-Lien Loan</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_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="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="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="tslx_CommonStockSharesIssuedInSettlementOfConvertibleNotesDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock issued in settlement of convertible notes, Shares</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonStockSharesIssuedInSettlementOfConvertibleNotesDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Shares Issued In Settlement Of Convertible Notes During The Period</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommonStockSharesIssuedInSettlementOfConvertibleNotesDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock shares issued in settlement of convertible notes during the period.</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_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_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_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Operating Activities</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_PurchasesAndOriginationsOfInvestmentsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Purchases and originations of investments, net.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PurchasesAndOriginationsOfInvestmentsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Purchases And Originations Of Investments Net</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PurchasesAndOriginationsOfInvestmentsNet_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="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_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="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="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_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_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_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="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated gross unrealized loss on tax cost investment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Estimated Gross Unrealized Loss on Tax Cost Investment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Estimated gross unrealized loss on tax cost investment.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGlobalMarketStrategiesCLOLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carlyle Global Market Strategies CLO Ltd.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGlobalMarketStrategiesCLOLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Carlyle Global Market Strategies C L O Ltd [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CarlyleGlobalMarketStrategiesCLOLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Carlyle Global Market Strategies CLO Ltd.</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_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_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="tslx_RepaymentsOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Repayments on investments.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RepaymentsOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Repayments On Investments</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RepaymentsOnInvestments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Repayments on investments</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="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="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="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_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="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="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="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="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_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_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="us-gaap_MinorityInterestOwnershipPercentageByParent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minority Interest Ownership Percentage By 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_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_DerivativeAssetInterestRateSwapFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative asset interest rate swap four.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Interest Rate Swap Four [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Asset Interest Rate Swap Four</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="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">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/terseLabel">Gain on extinguishment of debt</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_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="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="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="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="tslx_BankBillSwapBidRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BBSY</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BankBillSwapBidRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Bank Bill Swap Bid Rate [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BankBillSwapBidRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Bank Bill Swap Bid Rate.</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 Level2 [Member]</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">Available For Sale Securities Debt Securities</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_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_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_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="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_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="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="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_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_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="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_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="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_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_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="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="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="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_ControlledAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Controlled, affiliated investments.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ControlledAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Controlled Affiliated Investments [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ControlledAffiliatedInvestmentsMember_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="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="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_TwoThousandNineteenConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2019 Convertible Notes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandNineteenConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Nineteen Convertible Notes [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandNineteenConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand nineteen convertible notes member.</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 settlements</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="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/terseLabel">BTRS Holding Inc.</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_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_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="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_TaxCostOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax cost of investments</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxCostOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Cost of Investments</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxCostOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tax cost of investments.</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="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="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="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="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_GainLossOnSaleOfDerivatives_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net realized (gains) Losses on interest rate swaps</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfDerivatives_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Interest rate swaps</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfDerivatives_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized gains (losses) on derivatives</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfDerivatives_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Sale of Derivatives</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/label">Debt Instrument [Axis]</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_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders Equity [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_TreasuryStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Treasury Stock</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">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/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="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="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_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="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Foreign Currency Transactions And Translations 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="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="us-gaap_InvestmentBasisSpreadVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reference Rate and Spread</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="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="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="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="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_PerShareMarketValueAtEndPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Per Share Market Value At End Period.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PerShareMarketValueAtEndPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Per Share Market Value At End Period</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PerShareMarketValueAtEndPeriod_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_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="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="us-gaap_DeferredTaxAssetsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax asset</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets, Gross</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Tax Assets, Gross, Total</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="tslx_InvestmentsAtFairValueTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments at fair value.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsAtFairValueTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments At Fair Value [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsAtFairValueTextBlock_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_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_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="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net unrealized (gain) loss on investments</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net unrealized (gain) loss on investments</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">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="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">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="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_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_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="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_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">Minority Interest Ownership Percentage By Noncontrolling Owners</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="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="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="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financing Receivable Recorded Investment 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_InvestmentIncomeDividend_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income Dividend</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeDividend_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_InvestmentIncomeDividend_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_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_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value of Company's 2022 Convertible Notes, 2023 Notes, 2024 Notes and 2026 Notes</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="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="tslx_LineOfCreditFacilityAdditionalBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility additional borrowing capacity</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityAdditionalBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility Additional Borrowing Capacity</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityAdditionalBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Line of credit facility additional borrowing capacity.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsAndNetOperatingLossesRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net deferred tax liability pertaining to unrealized gains and net operating losses on investment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsAndNetOperatingLossesRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Liability Pertaining To Unrealized Gains And Net Operating Losses Related To Investments</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsAndNetOperatingLossesRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred tax liability pertaining to unrealized gains and net operating losses related to investments.</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="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_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_RepurchaseOfConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Repurchase of convertible notes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RepurchaseOfConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Repurchase of Convertible Notes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RepurchaseOfConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Repurchase of convertible notes.</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="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due April Two Thousand Twenty Five Two..</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due April Two Thousand Twenty Five Two [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAprilTwoThousandTwentyFiveTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($3,750 par, Due 4/2025)</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="tslx_DerivativeAssetInterestRateSwapEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative asset interest rate swap eight.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Interest Rate Swap Eight [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Asset Interest Rate Swap Eight</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="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_ManagementAndIncentiveFeesWaived_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Management and incentive fees waived</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementAndIncentiveFeesWaived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Management and incentive fees waived (Note 3)</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementAndIncentiveFeesWaived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Management and Incentive Fees Waived</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementAndIncentiveFeesWaived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Management and incentive fees waived.</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_ScheduleOfDividendsPayableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Dividends Payable [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="tslx_ConversionOfConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Conversion of convertible notes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConversionOfConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Conversion of convertible notes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConversionOfConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Conversion of Convertible Notes.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ConversionOfConvertibleNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Conversion of Convertible Notes.</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="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/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/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_OtherBookTaxDifferences_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other book-tax differences</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherBookTaxDifferences_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Book-tax Differences</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherBookTaxDifferences_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other book-tax differences.</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="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Available For Sale Securities [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_InterestRateSwapFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Fourteen</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Fourteen [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest Rate Swap Fourteen.</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="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="us-gaap_PositionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Position [Axis]</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="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated gross unrealized gains on tax cost investment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Estimated Gross Unrealized Gains on Tax Cost Investment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Estimated gross unrealized gains on tax cost investment.</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_DividendsPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable Current And Noncurrent</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">Dividends payable</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="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="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="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="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_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_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">Deferred Finance 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_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="srt_ScenarioForecastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scenario 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_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="us-gaap_DebtInstrumentConvertibleConversionPrice1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Convertible Conversion Price1</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, conversion price</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_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_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract]</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 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_InvestmentsBySecondaryCategorizationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments by Secondary Categorization [Domain]</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_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="tslx_AdditionalAggregatePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Additional aggregate principal amount.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdditionalAggregatePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Aggregate Principal Amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdditionalAggregatePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional aggregate principal amount</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_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_FirstLienLoanDueDecemberTwoThousandTwentyFiveThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due December Two Thousand Twenty Five Three.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due December Two Thousand Twenty Five Three [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueDecemberTwoThousandTwentyFiveThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($42,000 par, Due 12/2025)</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_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_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_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="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="us-gaap_EquitySecuritiesIndustryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Securities Industry [Member]</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="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="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="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_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="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="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_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_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="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_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="tslx_InterestRateSwapSevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap seven.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapSevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Seven [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapSevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Seven</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_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_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, convertible, threshold consecutive trading days</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Convertible, Threshold Consecutive Trading Days</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="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="currency_GBP_lbl" xlink:role="http://www.xbrl.org/2003/role/label">G B P</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_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_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_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_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_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract]</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/terseLabel">Non-Cash Financing Activities:</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_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_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="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 and offering costs</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="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="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_EquityAndOtherInvestments_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_EquityAndOtherInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity And Other Investments</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndOtherInvestments_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_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="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_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="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_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="tslx_FirstLienLoanDueNovemberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due November Two Thousand Twenty Six One.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due November Two Thousand Twenty Six One [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueNovemberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($54,859 par, Due 11/2026)</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="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="us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Selected Quarterly Financial Data</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Quarterly Financial Information [Table 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/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="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_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_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="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="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="tslx_InterestRateSwapElevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap eleven.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapElevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Eleven [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapElevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Eleven</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_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_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="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement Location [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_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_StructuredProductDueAprilTwoThousandThirtyOneTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured product due April two thousand thirty one two.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyOneTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Product Due April Two Thousand Thirty One Two [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredProductDueAprilTwoThousandThirtyOneTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Product Due April Two Thousand Thirty One Two</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchases of treasury stock</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total cost</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchases of treasury stock</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Value, Acquired, Cost Method</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="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="tslx_RevolvingCreditFacilityMaturityOnFebruaryFourTwoThousandTwentySixMember_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_RevolvingCreditFacilityMaturityOnFebruaryFourTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility Maturity on February Four Two Thousand Twenty Six [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnFebruaryFourTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving credit facility maturity on february four two thousand twenty six.</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 $17,760 and $19,147, respectively)</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="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="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="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_FirstLienLoanDueAugustTwoThousandTwentyFiveOneMember_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_FirstLienLoanDueAugustTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien loan Due August Two Thousand Twenty Five One.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueAugustTwoThousandTwentyFiveOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due August Two Thousand Twenty Five One [Member]</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="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Prepaid Deferred 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_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="us-gaap_QuarterlyFinancialInformationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Selected Quarterly Financial Data (Unaudited)</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_QuarterlyFinancialInformationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Quarterly Financial Information [Text Block]</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_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="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="tslx_InvestmentOwnedInitialAcquisitionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment owned initial acquisition date.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentOwnedInitialAcquisitionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned Initial Acquisition Date</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentOwnedInitialAcquisitionDate_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="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_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="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="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="tslx_DeferredOrganizationCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred organization costs</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredOrganizationCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Organization Costs</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredOrganizationCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred organization costs.</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_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_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_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="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="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_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="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_TaxCreditCarryforwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Credit Carryforward [Table]</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 issued who not opted dividend reinvestment plan and shares newly issued.</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 Issued Who Not Opted Dividend Reinvestment Plan And Shares Newly Issued Table [Text Block]</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_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_DeferredTaxAssetsLiabilitiesNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax liability offset by deferred tax asset pertaining to operating losses</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsLiabilitiesNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets, Net</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsLiabilitiesNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Tax Assets, Net, Total</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="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_OtherIncomeForTaxPurposesNotBook_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other income for tax purposes, not book.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherIncomeForTaxPurposesNotBook_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Income For Tax Purposes, Not Book</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherIncomeForTaxPurposesNotBook_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other income for tax purposes, not book.</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="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Treasury stock at cost; 664,250 and 296,044 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_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="tslx_DerivativeLiabilitiesInterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative liabilities interest rate swap.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeLiabilitiesInterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Liabilities Interest Rate Swap [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeLiabilitiesInterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Liabilities Interest Rate Swap</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_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="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of earnings per share basic and diluted table.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Earnings Per Share Basic And Diluted [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Earnings Per Share Basic And Diluted [Table]</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="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="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="tslx_OtherExpensesNotCurrentlyDeductible_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other expenses not currently deductible</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherExpensesNotCurrentlyDeductible_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other expenses not currently deductible</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherExpensesNotCurrentlyDeductible_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Expenses Not Currently Deductible</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherExpensesNotCurrentlyDeductible_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other expenses not currently deductible.</link:label>
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    <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_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="tslx_CordanceOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cordance Operations, LLC</link:label>
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    <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_UnrealizedGainsLossesOnIncomeTaxProvision_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Income tax provision</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedGainsLossesOnIncomeTaxProvision_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Unrealized gains losses on income tax provision.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PositionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Position [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnFairValueHedgeIneffectivenessNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Gain (Loss) on Fair Value Hedge Ineffectiveness, Net, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnFairValueHedgeIneffectivenessNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain Loss On Fair Value Hedge Ineffectiveness Net</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnFairValueHedgeIneffectivenessNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain (loss) on fair value hedge ineffectiveness, net</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="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="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_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/terseLabel">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/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="us-gaap_IncomeTaxAuthorityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Authority [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="us-gaap_ValuationTechniqueAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Technique [Axis]</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_DeferredTaxAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax asset offset by valuation allowance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets, Net of Valuation Allowance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Tax Assets, Net of Valuation Allowance, Total</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_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="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total</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">Profit Loss</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 in net assets resulting from operations</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_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">Foreign Currency Transaction Gain Loss Unrealized</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_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="tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends_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_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total Return Based On Market Value With Reinvestment Of Dividends.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Return Based On Market Value With Reinvestment Of Dividends</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>
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    <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="us-gaap_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="us-gaap_StockRepurchaseProgramExpirationDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Repurchase Program Expiration Date</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="tslx_InterestRateSwapNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap nine.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Nine [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Nine</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="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurements Fair Value Hierarchy [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="us-gaap_DebtConversionConvertedInstrumentAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Conversion Converted Instrument Amount1</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionConvertedInstrumentAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, principal converted amount</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_DerivativeAssetInterestRateSwapNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative asset interest rate swap nine.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Interest Rate Swap Nine [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Asset Interest Rate Swap Nine</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_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="tslx_TotalReturnBasedOnNetAssetValue_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="tslx_TotalReturnBasedOnNetAssetValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total Return Based On Net Asset Value.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnNetAssetValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Return Based On Net Asset Value</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">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_FirstLienLoanDueOctoberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Loan ($65,000 par, Due 10/2026)</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien Loan Due October Two Thousand Twenty Six one.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienLoanDueOctoberTwoThousandTwentySixOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Loan Due October Two Thousand Twenty Six One [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="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="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="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_IncreaseDecreaseInManagementFeesPayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in management fees payable to affiliate.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Management Fees Payable To Affiliate</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate_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="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="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_CostModelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cost model.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CostModelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cost Model [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CostModelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cost Model</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of tax character of shareholder distributions</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Tax Character Of Shareholder Distributions [Table Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of tax character of shareholder distributions.</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_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Upfront (Payments) / Receipts in derivative assets and liabilities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Upfront Payments Receipts In Derivative Assets And Liabilities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Upfront (Payments) / Receipts</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_DerivativeAssetInterestRateSwapElevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative asset interest rate swap eleven.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapElevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset Interest Rate Swap Eleven [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeAssetInterestRateSwapElevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Asset Interest Rate Swap Eleven</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Adjustment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustments:</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Adjustment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Adjustment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Adjustment</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_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">Foreign Currency Transaction Gain Loss Realized</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_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="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="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_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="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="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_DividendPayableDateToBePaidDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividend Payable Date To Be Paid Day Month And Year</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="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="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="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="tslx_LongTermCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Long-term capital gains.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LongTermCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Term Capital Gains</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LongTermCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Capital Gains</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanJanuaryTwoThousandTwentyFourMember_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_FirstLienRevolvingLoanJanuaryTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Revolving Loan January Two Thousand Twenty Four [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienRevolvingLoanJanuaryTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien revolving loan january two thousand twenty four.</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_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/terseLabel">Convertible Senior Notes Due 2022 [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/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="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="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 Level3 [Member]</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</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="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="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Average 1-month LIBOR 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/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 Rate1</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_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_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="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_InvestmentCompanyRepurchaseOfDebtPerShare_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Repurchase of Debt</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyRepurchaseOfDebtPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Repurchase of Debt</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyRepurchaseOfDebtPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Repurchase of Debt Per Share</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyRepurchaseOfDebtPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company repurchase of debt per share.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive fees on net capital gains accrued to affiliate.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fees On Net Capital Gains Accrued To Affiliate</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate_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_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="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/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/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="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 Level3</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="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="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="tslx_DelayedDrawAndMembershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Delayed Draw and Membership Interest</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawAndMembershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw and Membership Interest [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawAndMembershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Delayed Draw and Membership Interest [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecuredOvernightFinancingRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SOFR</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecuredOvernightFinancingRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Secured Overnight Financing Rate [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecuredOvernightFinancingRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Secured Overnight Financing Rate.</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_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="tslx_DerivativeLiabilitiesInterestRateSwapTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative liabilities interest rate swap two.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeLiabilitiesInterestRateSwapTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Liabilities Interest Rate Swap Two [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeLiabilitiesInterestRateSwapTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Liabilities Interest Rate Swap Two</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DueToAffiliateCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Due To Affiliate Current And Noncurrent</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DueToAffiliateCurrentAndNoncurrent_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_TwentyTwentyFourNotesMember_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_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="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_DebtInstrumentConvertibleMeasurementPeriodThresholdPercentageOfTradingPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, convertible, measurement period, threshold percentage of trading price</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtInstrumentConvertibleMeasurementPeriodThresholdPercentageOfTradingPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Convertible, Measurement Period, Threshold Percentage of Trading Price</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtInstrumentConvertibleMeasurementPeriodThresholdPercentageOfTradingPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument, convertible, measurement period, threshold percentage of trading price.</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="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">Debt Instrument Carrying Amount</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_PingIdentityCorporationMember_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_PingIdentityCorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ping Identity Corporation [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PingIdentityCorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ping Identity Corporation.</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_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="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_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="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_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="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_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="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_NetIncomeLossAvailableToCommonStockholdersDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Income Loss Available To Common Stockholders Diluted</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Numerator for diluted earnings per share</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseMember_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_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="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="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_InterestRateSwapThirteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Thirteen</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapThirteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Thirteen [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapThirteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap thirteen.</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/terseLabel">2026 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/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="currency_AUD_lbl" xlink:role="http://www.xbrl.org/2003/role/label">A U D</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="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_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/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/terseLabel">Other liabilities</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="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_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="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="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="us-gaap_DistributedEarnings_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_DistributedEarnings_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Distributed Earnings</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="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_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Related Party Transactions By Related Party [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_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="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_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="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="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="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_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="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock issued upon conversion of convertible notes, value</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, Conversion of Convertible Securities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_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="us-gaap_StockRepurchaseProgramAuthorizedAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Repurchase Program, Authorized Amount</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>
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