424(b)(2) Registration No.
333-276252

Subject to Completion

Preliminary Prospectus Supplement dated January 8, 2024

The information in this preliminary prospectus supplement is not complete and may be changed. A registration statement relating to these securities has been filed with and declared effective by the Securities and Exchange Commission. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

PROSPECTUS SUPPLEMENT

(To Prospectus dated December 22, 2023)

$                

    % Notes due

We are offering $                 in aggregate principal amount of     % notes due                     , which we refer to as the Notes. The Notes will mature on                     . We will pay interest on the Notes on                      and                      of each year, beginning on                     , 2024. We may redeem the Notes in whole or in part at any time or from time to time at the redemption price discussed under the caption “Description of Notes—Optional Redemption” in this prospectus supplement. In addition, holders of the Notes can require us to repurchase the Notes at 100% of their principal amount upon the occurrence of a Change of Control Repurchase Event (as defined herein). The Notes will be issued in minimum denominations of $2,000 and integral multiples of $1,000 in excess thereof.

The Notes will be our direct, general unsecured obligations and rank pari passu, or equal, with all existing and future unsecured unsubordinated indebtedness issued by us, but will rank senior to our future indebtedness that is expressly subordinated in right of payment to the Notes. We are a specialty finance company that has elected to be regulated as a business development company under the Investment Company Act of 1940. We seek to generate current income primarily through direct originations of senior secured loans and, to a lesser extent, originations of mezzanine and unsecured loans and investments in corporate bonds and equity securities.

As of September 30, 2023, our investment portfolio consisted of investments in 131 portfolio companies (including 42 structured credit investments, which include each series of collateralized loan obligation as a separate portfolio company investment) with an aggregate fair value of $3,113.3 million. We intend to continue to pursue an investment strategy focused primarily on direct origination of loans to middle-market companies domiciled in the United States.

We are an externally managed, closed-end, non-diversified management investment company. Sixth Street Specialty Lending Advisers, LLC, or the Adviser, acts as our investment adviser and administrator. We and the Adviser are part of Sixth Street Partners, LLC, a global investment firm with over $75 billion in assets under management as of September 30, 2023.

The companies in our investment portfolio are typically highly leveraged, and, in many cases, our investments in these companies are not rated by any rating agency. If these investments were rated, we believe that most would likely receive a rating of below investment grade (that is, below BBB- or Baa3, which is often referred to as “junk”). Our exposure to below investment grade instruments involves certain risks, including speculation with respect to the borrower’s capacity to pay interest and repay principal. The debt investments in our portfolio generally have a significant portion of principal due at the maturity of the investment, which would result in a substantial loss to us if such borrowers are unable to refinance or repay their debt at maturity.

Substantially all of our debt investments have variable interest rates that reset periodically based on interest rate benchmarks such as the Euro Interbank Offered Rate, the Canadian Dollar Offered Rate, the Secured Overnight Financing Rate, the Sterling Overnight Interbank Average Rate or the Prime Rate. As a result, significant increases in such interest rate benchmarks (or any replacement benchmarks) in the future would make it more difficult for these borrowers to service their obligations under the debt investments that we hold.

Investing in the Notes involves risks, including the risk of leverage, that are described in the “Risk Factors” section beginning on page S-9 of this prospectus supplement and page 24 of the accompanying prospectus and the matters discussed in the documents incorporated or deemed to be incorporated by reference in this prospectus supplement and the accompanying prospectus.

Please read this prospectus supplement and the accompanying prospectus, including any information incorporated by reference herein or therein, before investing and keep such documents for future reference. This prospectus supplement and the accompanying prospectus, and the documents incorporated by reference herein or therein, contain important information about us that a prospective investor ought to know before investing in our securities. Information required to be included in a Statement of Additional Information may be found in this prospectus supplement and the accompanying prospectus or incorporated by reference herein or therein. We also file periodic and current reports, proxy statements and other information about us with the Securities and Exchange Commission (the “SEC”). This information is available free of charge by contacting us at 888 7th Avenue, 41st Floor, New York, NY 10106, Attention: TSLX Investor Relations, by emailing us at IRTSLX@sixthstreet.com or visiting our website at http://www.sixthstreetspecialtylending.com. Information on our website is not incorporated into or a part of this prospectus supplement or the accompanying prospectus. The SEC also maintains a website at http://www.sec.gov that contains this information.

THE NOTES ARE NOT DEPOSITS OR OTHER OBLIGATIONS OF A BANK AND ARE NOT INSURED BY THE FEDERAL DEPOSIT INSURANCE CORPORATION OR ANY OTHER GOVERNMENT AGENCY.

Neither the SEC nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Delivery of the Notes in book-entry form only through The Depository Trust Company will be made on or about                 , 2024.

Joint Book-Running Managers

The date of this prospectus supplement is                     , 2024.

We have not, and the underwriters have not, authorized anyone to give you any information other than in this prospectus supplement, the accompanying prospectus or any information that we have incorporated by reference herein or therein, and we take no responsibility for any other information that others may give you. We are not, and the underwriters are not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus supplement and the accompanying prospectus, as well as the information incorporated by reference herein or therein, is accurate only as of the date of such documents. Our business, financial condition, results of operations and prospects may have changed since that date. We will update these documents to reflect material changes only as required by law.

Prospectus Supplement

TABLE OF CONTENTS

Prospectus

TABLE OF CONTENTS

S-i

S-ii

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement and the accompanying prospectus contain forward-looking statements that involve substantial risks and uncertainties. These forward-looking statements are not historical facts, but rather are based on current expectations, estimates and projections about us, our current and prospective portfolio investments, our industry, our beliefs, and our assumptions. Words such as “anticipates,” “expects,” “intends,” “plans,” “believes,” “seeks,” “estimates,” “would,” “should,” “targets,” “projects,” and variations of these words and similar expressions are intended to identify forward-looking statements. These statements are not guarantees of future performance and are subject to risks, uncertainties, and other factors, some of which are beyond our control and difficult to predict, that could cause actual results to differ materially from those expressed or forecasted in the forward-looking statements.

In addition to factors identified elsewhere in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein or therein, the following factors, among others, could cause actual results to differ materially from forward-looking statements or historical performance:

Although we believe that the assumptions on which these forward-looking statements are based are reasonable, some of those assumptions are based on the work of third parties and any of those assumptions could prove to be inaccurate; as a result, forward-looking statements based on those assumptions also could prove to be inaccurate. In light of these and other uncertainties, the inclusion of a projection or forward-looking statement in this prospectus supplement or the accompanying prospectus should not be regarded as a representation by us that our plans and objectives will be achieved. These risks and uncertainties include, among other things, those described or identified in “Risk Factors” in this prospectus supplement, the accompanying prospectus and in Part I, Item 1A of our 2022 Annual Report and in Part I, Item 1A of our 1Q 2023 Quarterly Report, our 2Q 2023 Quarterly Report and our 3Q 2023 Quarterly Report, any subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K we file after the date of this prospectus supplement, and those discussed in other documents we file with the SEC and elsewhere in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein or therein. You should not place undue reliance on these forward-looking statements, which apply only as of the date of this prospectus supplement. We do not undertake any obligation to update or revise any forward-looking statements or any other information contained herein or therein, except as required by applicable law.

S-1

S-2

S-3

S-4

S-5

S-6

S-7

S-8

RISK FACTORS

Investing in our securities involves a number of significant risks. You should carefully consider the risks set out below and the risk factors incorporated by reference in Part I, Item 1A, “Risk Factors,” in our 2022 Annual Report, Part I, Item IA, “Risk Factors,” in our Q1 2023 Quarterly Report, our Q2 2023 Quarterly Report and our Q3 2023 Quarterly Report, and in any subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K we file after the date of this prospectus supplement, together with the other information set forth in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference herein and therein, including our consolidated financial statements and the related notes thereto, and any free writing prospectus that we may authorize for use in connection with this offering, as updated by our subsequent filings under the Exchange Act, before making a decision about investing in our securities. The risks and uncertainties set out below and discussed in our 2022 Annual Report, our Q1 2023 Quarterly Report, Q2 2023 Quarterly Report, Q3 2023 Quarterly Report and in the accompanying prospectus are not the only ones we face. Additional risks and uncertainties not presently known to us or not presently deemed material by us may also materially and adversely affect our business, financial condition and results of operations. In such case, our net asset value and the trading price of our securities could decline, and you may lose all or part of your investment.

Risks Related to This Offering

The Notes are unsecured and therefore are effectively subordinated to any secured indebtedness we have currently incurred or may incur in the future.

The Notes are not secured by any of our assets or any of the assets of our subsidiaries. As a result, the Notes are effectively subordinated, or junior, to any secured indebtedness or other obligations we or our subsidiaries have currently incurred and may incur in the future (or any indebtedness that is initially unsecured that we later secure) to the extent of the value of the assets securing such indebtedness. In any liquidation, dissolution, bankruptcy or other similar proceeding, the holders of any of our existing or future secured indebtedness and the secured indebtedness of our subsidiaries may assert rights against the assets pledged to secure that indebtedness in order to receive full payment of their indebtedness before the assets may be used to pay other creditors, including the holders of the Notes. As of September 30, 2023, we had approximately $758.2 million aggregate principal amount of outstanding indebtedness under the Revolving Credit Facility. The Revolving Credit Facility is secured by a perfected first-priority security interest in substantially all the portfolio investments held by us and each guarantor party thereto; the indebtedness thereunder is therefore effectively senior to the Notes to the extent of the value of such assets.

The Notes are structurally subordinated to the indebtedness and other liabilities of our subsidiaries.

The Notes are obligations exclusively of TSLX and not of any of our subsidiaries. None of our subsidiaries is a guarantor of the Notes and the Notes are not required to be guaranteed by any subsidiaries we may acquire or create in the future. Except to the extent we are a creditor with recognized claims against our subsidiaries, all claims of creditors (including trade creditors) and holders of preferred stock, if any, of our subsidiaries will have priority over our equity interests in such subsidiaries (and therefore the claims of our creditors, including holders of the Notes) with respect to the assets of such subsidiaries. Even if we are recognized as a creditor of one or more of our subsidiaries, our claims would still be effectively subordinated to any security interests in the assets of any such subsidiary and to any indebtedness or other liabilities of any such subsidiary senior to our claims. Consequently, the Notes are structurally subordinated, or junior, to all existing and future indebtedness and other obligations (including trade payables) incurred by any of our subsidiaries, financing vehicles or similar facilities and any subsidiaries, financing vehicles or similar facilities that we may in the future acquire or establish. Our subsidiaries may incur substantial additional indebtedness in the future, all of which would be structurally senior to the Notes.

S-9

Our current indebtedness could adversely affect our business, financial condition and results of operations and our ability to meet our payment obligations under the Notes and our other debt.

As of September 30, 2023 our total consolidated indebtedness was approximately $1,705.7 million aggregate principal amount outstanding, of which approximately $758.2 million was secured indebtedness at the TSLX level and none of which was indebtedness of our subsidiaries, and approximately $947.5 million aggregate principal amount was unsecured indebtedness.

The use of debt could have significant consequences on our future operations, including:

Any of the above-listed factors could have an adverse effect on our business, financial condition and results of operations and our ability to meet our payment obligations under the Notes and our other debt.

Our ability to meet our payment and other obligations under our debt instruments depends on our ability to generate significant cash flow in the future. This, to some extent, is subject to general economic, financial, competitive, legislative and regulatory factors as well as other factors that are beyond our control.

We cannot assure you that our business will generate sufficient cash flow from operations or that future borrowings will be available to us under our Revolving Credit Facility or otherwise in an amount sufficient to enable us to pay our indebtedness, including the Notes, or to fund our other liquidity needs. We may need to refinance all or a portion of our indebtedness, including the Notes, on or before it matures. We cannot assure you that we will be able to refinance any of our indebtedness on commercially reasonable terms or at all. If we cannot service our indebtedness, we may have to take actions such as selling assets or seeking additional equity. We cannot assure you that any such actions, if necessary, could be effected on commercially reasonable terms or at all, or on terms that would not be disadvantageous to our stockholders or on terms that would not require us to breach the terms and conditions of our existing or future debt agreements, including our payment obligations under the Notes.

A downgrade, suspension or withdrawal of the credit rating assigned by a rating agency to us or the Notes, if any, or change in the debt markets could cause the liquidity or market value of the Notes to decline significantly.

Our credit ratings are an assessment by rating agencies of our ability to pay our debts when due. Consequently, real or anticipated changes in our credit ratings will generally affect the market value of the Notes. These credit ratings may not reflect the potential impact of risks relating to the structure or marketing of the Notes. Credit ratings are not a recommendation to buy, sell or hold any security, and may be revised or withdrawn at any time by the issuing organization in its sole discretion. Neither we nor any underwriter undertakes any obligation to maintain our credit ratings or to advise holders of Notes of any changes in our credit ratings. The Notes are rated by Moody’s Investor Service, or Moody’s, S&P Global Ratings, or S&P, and Fitch

S-10

Ratings, or Fitch. There can be no assurance that their respective credit ratings will remain for any given period of time or that such credit ratings will not be lowered or withdrawn entirely by Moody’s, S&P or Fitch if in any of their respective judgments future circumstances relating to the basis of the credit rating, such as adverse changes in our company, so warrant. The conditions of the financial markets and prevailing interest rates have fluctuated in the past and are likely to fluctuate in the future.

The indenture governing the Notes contains limited protection for holders of the Notes.

The indenture governing the Notes offers limited protection to holders of the Notes. The terms of the indenture and the Notes do not restrict our or any of our subsidiaries’ ability to engage in, or otherwise be a party to, a variety of corporate transactions, circumstances or events that could have an adverse impact on your investment in the Notes. In particular, the terms of the indenture and the Notes do not place any restrictions on our or our subsidiaries’ ability to:

Furthermore, the terms of the indenture and the Notes do not protect holders of the Notes in the event that we experience changes (including significant adverse changes) in our financial condition, results of operations or credit ratings, as they do not require that we or our subsidiaries adhere to any financial tests or ratios or specified levels of net worth, revenues, income, cash flow or liquidity.

Our ability to recapitalize, incur additional debt and take a number of other actions that are not limited by the terms of the Notes may have important consequences for you as a holder of the Notes, including making it more difficult for us to satisfy our obligations with respect to the Notes or negatively affecting the trading value of the Notes.

Certain of our current debt instruments include more protections for their holders than the indenture and the Notes. In addition, other debt we issue or incur in the future could contain more protections for its holders than the indenture and the Notes, including additional covenants and events of default. The issuance or incurrence of any such debt with incremental protections could affect the market for and trading levels and prices of the Notes.

S-11

The optional redemption provision may materially adversely affect your return on the Notes.

The Notes are redeemable in whole or in part upon certain conditions at any time or from time to time at our option. We may choose to redeem the Notes at times when prevailing interest rates are lower than the interest rate paid on the Notes. In this circumstance, you may not be able to reinvest the redemption proceeds in a comparable security at an effective interest rate as high as that of the Notes being redeemed.

If we default on our obligations to pay our other indebtedness, we may not be able to make payments on the Notes.

Any default under the agreements governing our indebtedness, including a default under our Revolving Credit Facility or under the 2024 Notes, 2026 Notes or 2028 Notes, or under other indebtedness to which we may be a party, that is not waived by the required lenders or holders and the remedies sought by the holders of such indebtedness could make us unable to pay principal, premium, if any, and interest on the Notes and substantially decrease the market value of the Notes.

If we are unable to generate sufficient cash flow and are otherwise unable to obtain funds necessary to meet required payments of principal, premium, if any, and interest on our indebtedness, or if we otherwise fail to comply with the various covenants, including financial and operating covenants, in the instruments governing our indebtedness, we could be in default under the terms of the agreements governing such indebtedness. In the event of such default, the holders of such indebtedness could elect to declare all the funds borrowed thereunder to be due and payable, together with accrued and unpaid interest, the lenders under our Revolving Credit Facility or other debt we may incur in the future could elect to terminate their commitments, cease making further loans and institute foreclosure proceedings against our assets, and we could be forced into bankruptcy or liquidation.

If our operating performance declines, we may in the future need to seek to obtain waivers from the required lenders or holders under the agreements governing our indebtedness, or other indebtedness that we may incur in the future, to avoid being in default. If we breach our covenants under the agreements governing our indebtedness and seek a waiver, we may not be able to obtain a waiver from the required lenders or holders. If this occurs, we would be in default and our lenders or debt holders could exercise their rights as described above, and we could be forced into bankruptcy or liquidation.

If we are unable to repay debt, lenders having secured obligations, including the lenders under our Revolving Credit Facility, could proceed against the collateral securing the debt. Because our Revolving Credit Facility, 2024 Notes, 2026 Notes and 2028 Notes have, the indenture will have, and any future debt will likely have, customary cross-default provisions, if the indebtedness thereunder, hereunder or under any future credit facility is accelerated, we may be unable to repay or finance the amounts due. See “Description of Notes” in this prospectus supplement and “Description of Our Debt Securities” in the accompanying prospectus.

We may not be able to repurchase the Notes upon a Change of Control Repurchase Event.

Upon the occurrence of a Change of Control Repurchase Event, as defined in the indenture that governs the Notes, as supplemented, subject to certain conditions, we will be required to offer to repurchase all outstanding Notes at 100% of their principal amount, plus accrued and unpaid interest. The source of funds for that purchase of Notes will be our available cash or cash generated from our operations or other potential sources, including borrowings, investment repayments, sales of assets or sales of equity. We cannot assure you that sufficient funds from such sources will be available at the time of any Change of Control Repurchase Event to make required repurchases of Notes tendered. The terms of the Revolving Credit Facility provide that certain change of control events will constitute an event of default thereunder entitling the lenders to accelerate any indebtedness outstanding under the credit facility at that time and to terminate the credit facility. In addition, the indentures governing our 2024 Notes, 2026 Notes and 2028 Notes each contain a provision that would require us to offer to purchase the respective 2024 Notes, 2026 Notes or 2028 Notes upon the occurrence of a fundamental change.

S-12

Any failure to comply with these provisions would constitute an event of default under each of the other agreements governing our indebtedness, including the indenture. Our future debt instruments also may contain similar restrictions and provisions. If the holders of the Notes exercise their right to require us to repurchase all the Notes upon a Change of Control Repurchase Event, the financial effect of this repurchase could cause a default under our future debt instruments, even if the Change of Control Repurchase Event itself would not cause a default. It is possible that we will not have sufficient funds at the time of the Change of Control Repurchase Event to make the required repurchase of the Notes or our other debt. See “Description of Notes—Offer to Repurchase Upon a Change of Control Repurchase Event.”

We cannot assure that an active trading market will be maintained for the Notes.

The Notes are a new issue of debt securities and there currently is no trading market for the Notes. We do not intend to apply for listing of the Notes on any securities exchange or for quotation of the Notes on any automated dealer quotation system. If no active trading market develops, you may not be able to resell your Notes at their fair market value or at all. If the Notes are traded after their initial issuance, they may trade at a discount from their initial offering price depending on prevailing interest rates, the market for similar securities, our credit ratings, general economic conditions, our financial condition, performance and prospects and other factors. Certain of the underwriters have advised us that they currently intend to make a market in the Notes but they are not obligated to do so. The underwriters may discontinue any market-making in the Notes at any time at their sole discretion. In addition, any market-making activity will be subject to limits imposed by law. Accordingly, we cannot assure you that a liquid trading market will be maintained for the Notes, that you will be able to sell your Notes at a particular time or that the price you receive when you sell will be favorable. To the extent an active trading market is not maintained, the liquidity and trading price for the Notes may be harmed. Accordingly, you may be required to bear the financial risk of an investment in the Notes for an indefinite period of time.

S-13

USE OF PROCEEDS

We estimate that the net proceeds we will receive from the sale of $                million aggregate principal amount of Notes in this offering will be approximately $                million, after deducting the underwriting discounts and commissions and estimated offering expenses payable by us.

We intend to use 100% of the net proceeds of this offering to pay down a portion of the outstanding indebtedness on the Revolving Credit Facility on or about the date of the closing of this offering. As of September 30, 2023, aggregate commitments under the facility were $1.710 billion. However, through reborrowing under the Revolving Credit Facility, we intend to make new investments in accordance with our investment objective and strategies described in this prospectus supplement and the accompanying prospectus. The stated maturity date of the Revolving Credit Facility is June 12, 2028 with respect to $1.465 billion of commitments, January 31, 2025 for $25.0 million of commitments, February 4, 2026 for $50.0 million of commitments and April 23, 2027 with respect to $170.0 million of commitments. As of September 30, 2023, amounts drawn under the facility bear interest at either the applicable reference rate plus an applicable credit spread adjustment, plus a margin of either 1.75% or 1.875%, or the base rate plus a margin of either 0.75% or 0.875%. See “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Financial Condition, Liquidity and Capital Resources—Revolving Credit Facility” in Part II, Item 2 of our 3Q 2023 Quarterly Report.

Affiliates of certain underwriters are lenders under the Revolving Credit Facility. Accordingly, affiliates of certain of the underwriters may receive more than 5% of the proceeds of this offering to the extent the proceeds are used to pay down a portion of the outstanding indebtedness under the Revolving Credit Facility.

S-14

CAPITALIZATION

The following table sets forth our consolidated capitalization at September 30, 2023. You should read this table together with “Use of Proceeds” described in this prospectus supplement and our most recent balance sheet included in our 2023 3Q Quarterly Report incorporated by reference in this prospectus supplement.

S-15

DESCRIPTION OF NOTES

The following description of the particular terms of the     % Notes due                  supplements and, to the extent inconsistent therewith, replaces the description of the general terms and provisions of the debt securities set forth in the accompanying prospectus.

We will issue the Notes under a base indenture dated as of the settlement date, between us and U.S. Bank Trust Company, National Association, as trustee (the “trustee”), as supplemented by a separate supplemental indenture, dated as of the settlement date of the Notes (the “first supplemental indenture”). As used in this section, all references to the indenture mean the base indenture as supplemented by the first supplemental indenture. The terms of the Notes include those expressly set forth in the indenture and those made part of the indenture by reference to the Trust Indenture Act of 1939, as amended, or the TIA.

The following description is a summary of the material provisions of the Notes and the indenture and does not purport to be complete. This summary is subject to and is qualified by reference to all the provisions of the Notes and the indenture, including the definitions of certain terms used in the indenture. We urge you to read these documents because they, and not this description, define your rights as a holder of the Notes.

For purposes of this description, references to “we,” “our” and “us” refer only to TSLX and not to any of its current or future subsidiaries and references to “subsidiaries” refer only to our consolidated subsidiaries and exclude any investments held by TSLX in the ordinary course of business which are not, under GAAP, consolidated on the financial statements of TSLX and its subsidiaries.

General

The Notes:

The indenture does not limit the amount of debt that may be issued by us or our subsidiaries under the indenture or otherwise. The indenture does not contain any financial covenants and does not restrict us from paying dividends or issuing or repurchasing our other securities. Other than restrictions described under “—Offer to Repurchase Upon a Change of Control Repurchase Event” and “—Merger, Consolidation or Sale of Assets” below, the indenture does not contain any covenants or other provisions designed to afford holders of the Notes protection in the event of a highly leveraged transaction involving us or in the event of a decline in our credit rating as the result of a takeover, recapitalization, highly leveraged transaction or similar restructuring involving us that could adversely affect such holders.

S-16

We may, without the consent of the holders, issue further additional Notes under the indenture with the same terms (except for the issue date, public offering price and, if applicable, the initial interest payment date) and with the same CUSIP numbers as the Notes in an unlimited aggregate principal amount; provided that such additional Notes must either be issued in a “qualified reopening” for U.S. federal income tax purposes, with less than a de minimis amount of original issue discount, or otherwise be part of the same issue as the Notes for U.S. federal income tax purposes.

We do not intend to list the Notes on any securities exchange or any automated dealer quotation system.

Payments on the Notes; Paying Agent and Registrar; Transfer and Exchange

We will pay the principal of, and interest on, the Notes in global form registered in the name of or held by DTC or its nominee in immediately available funds to DTC or its nominee, as the case may be, as the registered holder of such Global Note (as defined below).

Payment of principal of (and premium, if any) and any such interest on the Notes will be made at the corporate trust office of the paying agent, which initially shall be the trustee in such coin or currency of the United States of America as at the time of payment is legal tender for payment of public and private debts; provided, however, that, in the case of notes that are not in global form, at our option payment of interest may be made by check mailed to the address of the person entitled thereto as such address shall appear in the security register.

A holder of Notes may transfer or exchange Notes at the office of the registrar in accordance with the indenture. A holder may be required, among other things, to furnish appropriate endorsements and transfer documents. No service charge will be imposed by us, the trustee or the registrar for any registration of transfer or exchange of Notes, but we may require a holder to pay a sum sufficient to cover any transfer tax or other similar governmental charge required by law or permitted by the indenture. The transferor of any Note shall provide or cause to be provided to the trustee, upon reasonable request therefore, all information necessary to allow the trustee to comply with any applicable tax reporting obligations, including without limitation any cost basis reporting obligations under Internal Revenue Code Section 6045. The trustee may rely on information provided to it and shall have no responsibility to verify or ensure the accuracy of such information.

The registered holder of a Note will be treated as its owner for all purposes.

Interest

The Notes bear cash interest at a rate of     % per year until maturity. Interest on the Notes will accrue from                 , 2024 or from the most recent date on which interest has been paid or duly provided for. Interest is payable semiannually in arrears on                  and                  of each year, beginning on                 , 2024.

Interest will be paid to the person in whose name a Note is registered at 5:00 p.m. New York City time (the “close of business”) on                  or                  (whether or not a business day), as the case may be, immediately preceding the relevant interest payment date. Interest on the Notes will be computed on the basis of a 360-day year composed of twelve 30-day months.

If any interest payment date, redemption date, the maturity date or any earlier required repurchase date upon a Change of Control Repurchase Event (defined below) of a Note falls on a day that is not a business day, the required payment will be made on the next succeeding business day and no interest on such payment will accrue in respect of the delay. The term “business day” means, with respect to any Note, any day other than a Saturday, a Sunday or a day on which banking institutions in New York or the city in which the corporate trust office is located are authorized or obligated by law or executive order to close.

S-17

Ranking

The Notes are our direct, general unsecured obligations that rank:

As of September 30, 2023, our total consolidated indebtedness was approximately $1,705.7 million aggregate principal amount outstanding, of which approximately $758.2 million was secured indebtedness at the TSLX level and none of which was indebtedness of our subsidiaries. After giving effect to the issuance of the Notes, and assuming the net proceeds therefrom are used to repay outstanding borrowings under the Revolving Credit Facility, our total consolidated indebtedness would have been approximately $                 million aggregate principal amount outstanding as of September 30, 2023. See “Capitalization.”

In the event of our bankruptcy, liquidation, reorganization or other winding up, our assets that secure secured debt will be available to pay obligations on the Notes only after all indebtedness under such secured debt has been repaid in full from such assets. We advise you that there may not be sufficient assets remaining to pay amounts due on any or all the Notes then outstanding.

Optional Redemption

Any exercise of our option to redeem the Notes will be done in compliance with the 1940 Act. Prior to                  (                 month[s] prior to their maturity date) (the “Par Call Date”), we may redeem the Notes at our option, in whole or in part, at any time and from time to time, at a redemption price (expressed as a percentage of principal amount and rounded to three decimal places) equal to the greater of:

(1) (a) the sum of the present values of the remaining scheduled payments of principal and interest thereon discounted to the redemption date (assuming the Notes matured on the Par Call Date) on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the Treasury Rate plus                  basis points less (b) interest accrued to the date of redemption, and

(2) 100% of the principal amount of the Notes to be redeemed,

plus, in either case, accrued and unpaid interest thereon to the redemption date.

On or after the Par Call Date, we may redeem the Notes, in whole or in part, at any time and from time to time, at a redemption price equal to 100% of the principal amount of the Notes being redeemed plus accrued and unpaid interest thereon to the redemption date.

“Treasury Rate” means, with respect to any redemption date, the yield determined by us in accordance with the following two paragraphs.

S-18

The Treasury Rate shall be determined by us after 4:15 p.m., New York City time (or after such time as yields on U.S. government securities are posted daily by the Board of Governors of the Federal Reserve System), on the third business day preceding the redemption date based upon the yield or yields for the most recent day that appear after such time on such day in the most recent statistical release published by the Board of Governors of the Federal Reserve System designated as “Selected Interest Rates (Daily)—H.15” (or any successor designation or publication) (“H.15”) under the caption “U.S. government securities–Treasury constant maturities–Nominal” (or any successor caption or heading) (“H.15 TCM”). In determining the Treasury Rate, we shall select, as applicable: (1) the yield for the Treasury constant maturity on H.15 exactly equal to the period from the redemption date to the Par Call Date (the “Remaining Life”); or (2) if there is no such Treasury constant maturity on H.15 exactly equal to the Remaining Life, the two yields – one yield corresponding to the Treasury constant maturity on H.15 immediately shorter than and one yield corresponding to the Treasury constant maturity on H.15 immediately longer than the Remaining Life – and shall interpolate to the Par Call Date on a straight-line basis (using the actual number of days) using such yields and rounding the result to three decimal places; or (3) if there is no such Treasury constant maturity on H.15 shorter than or longer than the Remaining Life, the yield for the single Treasury constant maturity on H.15 closest to the Remaining Life. For purposes of this paragraph, the applicable Treasury constant maturity or maturities on H.15 shall be deemed to have a maturity date equal to the relevant number of months or years, as applicable, of such Treasury constant maturity from the redemption date.

If on the third business day preceding the redemption date H.15 TCM is no longer published, we shall calculate the Treasury Rate based on the rate per annum equal to the semi-annual equivalent yield to maturity at 11:00 a.m., New York City time, on the second business day preceding such redemption date of the United States Treasury security maturing on, or with a maturity that is closest to, the Par Call Date, as applicable. If there is no United States Treasury security maturing on the Par Call Date but there are two or more United States Treasury securities with a maturity date equally distant from the Par Call Date, one with a maturity date preceding the Par Call Date and one with a maturity date following the Par Call Date, we shall select the United States Treasury security with a maturity date preceding the Par Call Date. If there are two or more United States Treasury securities maturing on the Par Call Date or two or more United States Treasury securities meeting the criteria of the preceding sentence, we shall select from among these two or more United States Treasury securities the United States Treasury security that is trading closest to par based upon the average of the bid and asked prices for such United States Treasury securities at 11:00 a.m., New York City time. In determining the Treasury Rate in accordance with the terms of this paragraph, the semi-annual yield to maturity of the applicable United States Treasury security shall be based upon the average of the bid and asked prices (expressed as a percentage of principal amount) at 11:00 a.m., New York City time, of such United States Treasury security, and rounded to three decimal places.

Our actions and determinations in determining the redemption price shall be conclusive and binding for all purposes, absent manifest error. The trustee will not be responsible or liable for determining, confirming, or verifying the redemption price.

Notice of any redemption will be mailed or electronically delivered (or otherwise transmitted in accordance with the depositary’s procedures) at least 10 days but not more than 60 days before the redemption date to each holder of Notes to be redeemed. Any exercise of our option to redeem the Notes will be done in compliance with the 1940 Act.

In the case of a partial redemption, selection of the Notes for redemption will be made pro rata, by lot or by such other method as the Trustee deems appropriate and fair with the prior written consent of the Company. No Notes of a principal amount of $2,000 or less will be redeemed in part. If any Note is to be redeemed in part only, the notice of redemption that relates to the note will state the portion of the principal amount of the Note to be redeemed. A new note in a principal amount equal to the unredeemed portion of the Note will be issued in the name of the holder of the Note upon surrender for cancellation of the original Note. For so long as the Notes are held by DTC, Euroclear or Clearstream (or another depositary), the redemption of the Notes shall be done in accordance with the policies and procedures of the depositary.

S-19

Unless we default in payment of the redemption price, on and after the redemption date interest will cease to accrue on the Notes or portions thereof called for redemption.

Offer to Repurchase Upon a Change of Control Repurchase Event

If a Change of Control Repurchase Event occurs, unless we have exercised our right to redeem the Notes in full, we will make an offer to each holder of Notes to repurchase all or any part (in minimum denominations of $2,000 and integral multiples of $1,000 principal amount thereabove) of that holder’s Notes at a repurchase price in cash equal to 100% of the aggregate principal amount of Notes repurchased plus any accrued and unpaid interest on the Notes repurchased to the date of purchase. Within 30 days following any Change of Control Repurchase Event or, at our option, prior to any Change of Control, but after the public announcement of the Change of Control, we will send a notice to each holder and the trustee describing the transaction or transactions that constitute or may constitute the Change of Control Repurchase Event and offering to repurchase Notes on the payment date specified in the notice, which date will be no earlier than 30 days and no later than 60 days from the date such notice is sent. The notice shall, if sent prior to the date of consummation of the Change of Control, state that the offer to purchase is conditioned on the Change of Control Repurchase Event occurring on or prior to the payment date specified in the notice. We will comply with the requirements of Rule 14e-1 under the Exchange Act and any other securities laws and regulations thereunder to the extent those laws and regulations are applicable in connection with the repurchase of the Notes as a result of a Change of Control Repurchase Event. To the extent that the provisions of any securities laws or regulations conflict with the Change of Control Repurchase Event provisions of the Notes, we will comply with the applicable securities laws and regulations and will not be deemed to have breached our obligations under the Change of Control Repurchase Event provisions of the Notes by virtue of such conflict.

On the Change of Control Repurchase Event payment date, subject to extension if necessary to comply with the provisions of the 1940 Act, we will, to the extent lawful:

The paying agent will promptly remit to each holder of Notes properly tendered the purchase price for the Notes, and the trustee will promptly authenticate and mail (or cause to be transferred by book-entry) to each holder a new Note equal in principal amount to any unpurchased portion of any Notes surrendered; provided that each new Note will be in a minimum principal amount of $2,000 or an integral multiple of $1,000 in excess thereof.

We will not be required to make an offer to repurchase the Notes upon a Change of Control Repurchase Event if a third party makes an offer in the manner, at the times and otherwise in compliance with the requirements for an offer made by us and such third party purchases all Notes properly tendered and not withdrawn under its offer.

The source of funds that will be required to repurchase Notes in the event of a Change of Control Repurchase Event will be our available cash or cash generated from our operations or other potential sources, including funds provided by a purchaser in the Change of Control transaction, borrowings, sales of assets or sales of equity. We cannot assure you that sufficient funds from such sources will be available at the time of any Change of Control Repurchase Event to make required repurchases of Notes tendered. The terms of our credit facility provide that certain change of control events will constitute an event of default thereunder entitling the lenders to accelerate any indebtedness outstanding under the credit facility at that time and to terminate the credit

S-20

facility. In addition, the indentures governing the 2024 Notes, 2026 Notes and 2028 Notes each contains a provision that would require us to offer to purchase the respective 2024 Notes, 2026 Notes or 2028 Notes upon the occurrence of a fundamental change. A failure to purchase any tendered 2024 Notes, 2026 Notes or 2028 Notes would constitute an event of default under the applicable indenture, which would, in turn, constitute a default under our credit facility and the indenture. See “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Financial Condition, Liquidity and Capital Resources” in our Q3 2023 Quarterly Report, which is incorporated by reference herein, for a general discussion of our indebtedness. Our future debt instruments may contain similar restrictions and provisions. If the holders of the Notes exercise their right to require us to repurchase Notes upon a Change of Control Repurchase Event, the financial effect of this repurchase could cause a default under our future debt instruments, even if the Change of Control Repurchase Event itself would not cause a default. It is possible that we will not have sufficient funds at the time of the Change of Control Repurchase Event to make the required repurchase of the Notes or our other debt. See “Risk Factors—Risks Relating to the Notes—We may not be able to repurchase the Notes upon a Change of Control Repurchase Event.”

The definition of “Change of Control” includes a phrase relating to the direct or indirect sale, transfer, conveyance or other disposition of “all or substantially all” of our properties or assets and those of our subsidiaries taken as a whole. Although there is a limited body of case law interpreting the phrase “substantially all,” there is no precise, established definition of the phrase under applicable law. Accordingly, the ability of a holder of Notes to require us to repurchase the Notes as a result of a sale, transfer, conveyance or other disposition of less than all of our assets and the assets of our subsidiaries taken as a whole to another person or group may be uncertain.

For purposes of the Notes:

“Below Investment Grade Rating Event” means the Notes are downgraded below Investment Grade by all three Rating Agencies on any date from the date of the public notice of an arrangement that results in a Change of Control until the end of the 60-day period following public notice of the occurrence of a Change of Control (which period shall be extended so long as the rating of the Notes is under publicly announced consideration for possible downgrade by either of the Rating Agencies); provided that a Below Investment Grade Rating Event otherwise arising by virtue of a particular reduction in rating shall not be deemed to have occurred in respect of a particular Change of Control (and thus shall not be deemed a Below Investment Grade Rating Event for purposes of the definition of Change of Control Repurchase Event hereunder) if the Rating Agencies making the reduction in rating to which this definition would otherwise apply do not announce or publicly confirm or inform us in writing that the reduction was the result, in whole or in part, of any event or circumstance comprised of or arising as a result of, or in respect of, the applicable Change of Control (whether or not the applicable Change of Control shall have occurred at the time of the Below Investment Grade Rating Event).

“Change of Control” means the occurrence of any of the following:

S-21

“Change of Control Repurchase Event” means the occurrence of a Change of Control and a Below Investment Grade Rating Event.

“Controlled Subsidiary” means any subsidiary of TSLX, 50% or more of the outstanding equity interests of which are owned by TSLX and its direct or indirect subsidiaries and of which TSLX possesses, directly or indirectly, the power to direct or cause the direction of the management or policies, whether through the ownership of voting equity interests, by agreement or otherwise.

“Fitch” means Fitch Ratings, Inc., also known as Fitch Ratings, or any successor thereto.

“Investment Grade” means a rating of BBB-or better by Fitch (or its equivalent under any successor rating categories of Fitch), BBB-or better by S&P (or its equivalent under any successor rating categories of S&P) and Baa3 or better by Moody’s (or its equivalent under any successor rating categories of Moody’s) (or, in each case, if such Rating Agency ceases to rate the Notes for reasons outside of our control, the equivalent investment grade credit rating from any Rating Agency selected by us as a replacement Rating Agency).

“Moody’s” means Moody’s Investor Service, or any successor thereto.

“Permitted Holders” means (i) us, (ii) one or more of our Controlled Subsidiaries and (iii) Sixth Street Specialty Lending Advisers, LLC or any affiliate of Sixth Street Specialty Lending Advisers, LLC that is organized under the laws of a jurisdiction located in the United States of America and in the business of managing or advising clients.

“Rating Agency” means:

“S&P” means S&P Global Ratings or any successor thereto.

“Voting Stock” as applied to stock of any person, means shares, interests, participations or other equivalents in the equity interest (however designated) in such person having ordinary voting power for the election of a majority of the directors (or the equivalent) of such person, other than shares, interests, participations or other equivalents having such power only by reason of the occurrence of a contingency.

Covenants

In addition to the covenants described in the base indenture, the following covenants shall apply to the Notes. To the extent of any conflict or inconsistency between the base indenture and the following covenants, the following covenants shall govern:

Merger, Consolidation or Sale of Assets

The indenture provides that we will not merge or consolidate with or into any other person (other than a merger of a wholly owned subsidiary into us), or sell, transfer, lease, convey or otherwise dispose of all or substantially all our property (provided that, for the avoidance of doubt, a pledge of assets pursuant to any

S-22

secured debt instrument of TSLX or its Controlled Subsidiaries shall not be deemed to be any such sale, transfer, lease, conveyance or disposition) in any one transaction or series of related transactions unless:

For the purposes of this covenant, the sale, transfer, lease, conveyance or other disposition of all the property of one or more of our subsidiaries, which property, if held by us instead of such subsidiaries, would constitute all or substantially all of our property on a consolidated basis, shall be deemed to be the transfer of all or substantially all of our property.

Although there is a limited body of case law interpreting the phrase “substantially all”, there is no precise established definition of the phrase under applicable law. Accordingly, in certain circumstances there may be a degree of uncertainty as to whether a particular transaction would involve “all or substantially all” of the properties or assets of a person. As a result, it may be unclear as to whether the merger, consolidation or sale of assets covenant would apply to a particular transaction as described above absent a decision by a court of competent jurisdiction. Although these types of transactions are permitted under the indenture, certain of the foregoing transactions could constitute a Change of Control that results in a Change of Control Repurchase Event permitting each holder to require us to repurchase the Notes of such holder as described above.

An assumption by any person of obligations under the Notes and the indenture might be deemed for U.S. federal income tax purposes to be an exchange of the Notes for new Notes by the holders thereof, resulting in recognition of gain or loss for such purposes and possibly other adverse tax consequences to the holders. Holders should consult their own tax advisors regarding the tax consequences of such an assumption.

Other Covenants

S-23

Events of Default

Each of the following is an event of default:

If an event of default occurs and is continuing and a responsible officer of the Trustee has received written notice or has actual knowledge thereof, then and in every such case (other than an event of default specified in item (6) above) the trustee or the holders of at least 25% in principal amount of the outstanding Notes may declare the entire principal amount of Notes to be due and immediately payable, by a notice in writing to us (and to the trustee if given by the holders), and upon any such declaration such principal or specified portion thereof shall become immediately due and payable. Notwithstanding the foregoing, in the case of the events of bankruptcy, insolvency or reorganization described in item (6) above, 100% of the principal of and accrued and unpaid interest on the Notes will automatically become due and payable.

At any time after a declaration of acceleration with respect to the Notes has been made and before a judgment or decree for payment of the money due has been obtained by the trustee, the holders of a majority in principal amount of the outstanding Notes, by written notice to us and the trustee, may rescind and annul such declaration and its consequences if (i) we have paid or deposited with the trustee a sum sufficient to pay all overdue installments of interest, if any, on all outstanding Notes, the principal of (and premium, if any, on) all outstanding Notes that have become due otherwise than by such declaration of acceleration and interest thereon at the rate or rates borne by or provided for in such Notes, to the extent that payment of such interest is lawful interest upon overdue installments of interest at the rate or rates borne by or provided for in such Notes, and all sums paid or advanced by the trustee and the reasonable compensation, expenses, disbursements and advances of the trustee, its agents and counsel, and (ii) all events of default with respect to the Notes, other than the

S-24

nonpayment of the principal of (or premium, if any, on) or interest on such Notes that have become due solely by such declaration of acceleration, have been cured or waived. No such rescission will affect any subsequent default or impair any right consequent thereon.

No holder of Notes will have any right to institute any proceeding, judicial or otherwise, with respect to the indenture, or for the appointment of a receiver or trustee, or for any other remedy under the indenture, unless:

Notwithstanding any other provision in the indenture, the holder of any Note shall have the right, which is absolute and unconditional, to receive payment of the principal of (and premium, if any, on) and interest, if any, on such Note on the stated maturity or maturity expressed in such Note (or, in the case of redemption, on the redemption date or, in the case of repayment at the option of the holders, on the repayment date) and to institute suit for the enforcement of any such payment, and such rights shall not be impaired without the consent of such holder.

The trustee shall be under no obligation to exercise any of the rights or powers vested in it by the indenture at the request or direction of any of the holders of the Notes unless such holders shall have offered to the trustee security or indemnity satisfactory to the trustee against the costs, expenses and liabilities which might be incurred by it in compliance with such request or direction. Subject to the foregoing, the holders of a majority in principal amount of the outstanding Notes shall have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee or exercising any trust or power conferred on the trustee with respect to the Notes, provided that (i) such direction shall not be in conflict with any rule of law or with this indenture, (ii) the trustee may take any other action deemed proper by the trustee that is not inconsistent with such direction and (iii) the trustee need not take any action that it determines in good faith may involve it in personal liability or be unjustly prejudicial (it being understood that the trustee does not have an affirmative duty to ascertain whether or not any such directions are unduly prejudicial to such holders) to the holders of Notes not consenting.

The holders of not less than a majority in principal amount of the outstanding Notes may on behalf of the holders of all of the Notes waive any past default under the indenture with respect to the Notes and its consequences, except a default (i) in the payment of (or premium, if any, on) or interest, if any, on any Note, or (ii) in respect of a covenant or provision of the indenture which cannot be modified or amended without the consent of the holder of each outstanding Note affected. Upon any such waiver, such default shall cease to exist, and any event of default arising therefrom shall be deemed to have been cured, for every purpose, but no such waiver shall extend to any subsequent or other default or event of default or impair any right consequent thereto.

We are required to deliver to the trustee, within 120 days after the end of each fiscal year, an officers’ certificate stating that to the knowledge of the signers whether we are in default in the performance of any of the terms, provisions or conditions of the indenture.

Within 90 days after the occurrence of any default under the indenture with respect to the Notes, the trustee shall transmit notice of such default actually known to a responsible officer of the trustee, unless such default

S-25

shall have been cured or waived; provided, however, that, except in the case of a default in the payment of the principal of (or premium, if any, on) or interest, if any, on any Note, the trustee shall be protected in withholding such notice if and so long as it in good faith determines that withholding of such notice is in the interest of the holders of the Notes.

Satisfaction and Discharge; Defeasance

We may satisfy and discharge our obligations under the indenture by delivering to the securities registrar for cancellation all outstanding Notes or by depositing with the trustee or delivering to the holders, as applicable, after the Notes have become due and payable, or otherwise, moneys sufficient to pay all of the outstanding Notes and paying all other sums payable under the indenture by us. Such discharge is subject to terms contained in the indenture.

In addition, the Notes are subject to defeasance and covenant defeasance, in each case, in accordance with the terms of the indenture. Defeasance means that, subject to the satisfaction of certain conditions, including, but not limited to, (i) depositing in trust for the benefit of the holders of the Notes a combination of money and/or U.S. government or U.S. government agency notes or bonds that will generate enough cash, in the opinion of a nationally recognized investment bank, appraisal firm or firm of independent public accountants, to make interest, principal and any other payments on the Notes on their various due dates and (ii) delivering to the trustee an opinion of counsel stating that (a) we have received from, or there has been published by, the Internal Revenue Service (the “IRS”) a ruling, or (b) since the date of execution of the Indenture, there has been a change in the applicable U.S. federal income tax law, in either case to the effect that, and based thereon, the holders of the Notes and any coupons appertaining thereto will not recognize income, gain or loss for U.S. federal income tax purposes as a result of such defeasance and will be subject to U.S. federal income tax on the same amounts, in the same manner and at the same times as would have been the case if such defeasance had not occurred, we can legally release ourselves from all payment and other obligations on the Notes. Covenant defeasance means that, subject to the satisfaction of certain conditions, including, but not limited to, (i) depositing in trust for the benefit of the holders of the Notes a combination of money and/or U.S. government or U.S. government agency notes or bonds that will generate enough cash, in the opinion of a nationally recognized investment bank, appraisal firm or firm of independent public accountants, to make interest, principal and any other payments on the Notes on their various due dates and (ii) delivering to the trustee an opinion of counsel to the effect that the holders of the Notes and any coupons appertaining thereto will not recognize income, gain or loss for U.S. federal income tax purposes as a result of such covenant defeasance and will be subject to U.S. federal income tax on the same amounts, in the same manner and at the same times as would have been the case if such covenant defeasance had not occurred, we will be released from some of the restrictive covenants in the indenture.

Trustee

U.S. Bank Trust Company, National Association, is the trustee, security registrar and paying agent. U.S. Bank Trust Company, National Association, in its capacity, including without limitation as trustee, security registrar and paying agent, assumes no responsibility (or liability) for the accuracy, correctness, adequacy, or completeness of the information concerning us or our affiliates or any other party contained in this prospectus supplement and accompanying prospectus or the related documents or for any failure by us or any other party to disclose events that may have occurred and may affect the significance or accuracy of such information, or for any information provided to it by us, including but not limited to settlement amounts and any other information. Neither the trustee nor any paying agent shall be responsible for determining whether any Change of Control or Below Investment Grade Rating Event has occurred and whether any Change of Control offer with respect to the Notes is required.

We may maintain banking relationships in the ordinary course of business with the trustee and its affiliates.

S-26

“corporate trust office” means the corporate trust office of the Trustee, at which at any particular time its corporate trust business with respect to the Indenture shall be administered, which office is currently located at U.S. Bank Trust Company, National Association, 800 Nicollet Mall, Minneapolis, Minnesota 55402.

In no event shall the Trustee be responsible or liable for any failure or delay in the performance of its obligations hereunder arising out of or caused by, directly or indirectly, forces beyond its control, including, without limitation any act or provision of any present or future law or regulation or governmental authority, natural disaster, strikes, work stoppages, accidents, acts of war or terrorism, civil or military disturbances, nuclear or natural catastrophes or acts of God, labor dispute, disease, epidemic or pandemic, quarantine, national emergency and interruptions, loss or malfunctions of utilities, communications or computer (software and hardware) services, communications system failure, malware or ransomware or other unavailability of the Federal Reserve Bank wire or facsimile or telex system or other funds transfer system or other wire or communication facility or unavailability of any securities clearing system; it being understood that the Trustee shall use reasonable efforts that are consistent with accepted practices in the banking industry to resume performance as soon as practicable under the circumstances.”

Each of the trustee, security registrar, and paying agent will be entitled to those certain rights, privileges, immunities, indemnities, limitations of liability, and protections, as more fully set forth in the indenture.

Governing Law

The indenture provides that it and the Notes shall be governed by and construed in accordance with the laws of the State of New York, without regard to principles of conflicts of laws that would cause the application of laws of another jurisdiction.

Book-Entry, Settlement and Clearance

Global Notes

The Notes will be initially issued in the form of one or more registered Notes in global form, without interest coupons (the “Global Notes”). Upon issuance, each of the Global Notes will be deposited with the trustee as custodian for DTC and registered in the name of Cede & Co., as nominee of DTC.

Ownership of beneficial interests in a Global Note will be limited to persons who have accounts with DTC (“DTC participants”) or persons who hold interests through DTC participants. We expect that under procedures established by DTC:

Beneficial interests in Global Notes may not be exchanged for Notes in physical, certificated form except in the limited circumstances described below.

Book-Entry Procedures for Global Notes

All interests in the Global Notes will be subject to the operations and procedures of DTC. We provide the following summary of those operations and procedures solely for the convenience of investors. The operations and procedures of DTC are controlled by that settlement system and may be changed at any time. Neither we, the trustee (in any of its capacities) nor the underwriters are responsible for those operations or procedures.

S-27

DTC has advised us that it is:

DTC was created to hold securities for its participants and to facilitate the clearance and settlement of securities transactions between its participants through electronic book-entry changes to the accounts of its participants. DTC’s participants include securities brokers and dealers, including the underwriters; banks and trust companies; clearing corporations and other organizations. Indirect access to DTC’s system is also available to others such as banks, brokers, dealers and trust companies; these indirect participants clear through or maintain a custodial relationship with a DTC participant, either directly or indirectly. Investors who are not DTC participants may beneficially own securities held by or on behalf of DTC only through DTC participants or indirect participants in DTC.

So long as DTC’s nominee is the registered owner of a Global Note, that nominee will be considered the sole owner or holder of the Notes represented by that Global Note for all purposes under the indenture. Except as provided below, owners of beneficial interests in a Global Note:

As a result, each investor who owns a beneficial interest in a Global Note must rely on the procedures of DTC to exercise any rights of a holder of Notes under the indenture (and, if the investor is not a participant or an indirect participant in DTC, on the procedures of the DTC participant through which the investor owns its interest).

Payments of principal and interest with respect to the Notes represented by a Global Note will be made by the trustee to DTC’s nominee as the registered holder of the Global Note. Neither we nor the trustee will have any responsibility or liability for the payment of amounts to owners of beneficial interests in a Global Note, for any aspect of the records relating to or payments made on account of those interests by DTC, or for maintaining, supervising or reviewing any records of DTC relating to those interests.

Payments by participants and indirect participants in DTC to the owners of beneficial interests in a Global Note will be governed by standing instructions and customary industry practice and will be the responsibility of those participants or indirect participants and DTC.

Cross-market transfers of beneficial interests in Global Notes between DTC participants, on the one hand, and Euroclear or Clearstream participants, on the other hand, will be effected within DTC through the DTC participants that are acting as depositaries for Euroclear and Clearstream. To deliver or receive an interest in a Global Note held in a Euroclear or Clearstream account, an investor must send transfer instructions to Euroclear or Clearstream, as the case may be, under the rules and procedures of that system and within the established deadlines of that system. If the transaction meets its settlement requirements, Euroclear or Clearstream, as the case may be, will send instructions to its DTC depositary to take action to effect final settlement by delivering or receiving interests in the relevant Global Notes in DTC, and making or receiving payment under normal procedures for same-day funds settlement applicable to DTC. Euroclear and Clearstream participants may not deliver instructions directly to the DTC depositaries that are acting for Euroclear or Clearstream.

S-28

Because the settlement of cross-market transfers takes place during New York business hours, DTC participants may employ their usual procedures for sending securities to the applicable DTC participants acting as depositaries for Euroclear and Clearstream. The sale proceeds will be available to the DTC participant seller on the settlement date. Thus, to a DTC participant, a cross-market transaction will settle no differently from a trade between two DTC participants. Because of time zone differences, the securities account of a Euroclear or Clearstream participant that purchases an interest in a Global Note from a DTC participant will be credited on the business day for Euroclear or Clearstream immediately following the DTC settlement date. Cash received in Euroclear or Clearstream from the sale of an interest in a Global Note to a DTC participant will be reflected in the account of the Euroclear of Clearstream participant the following business day, and receipt of the cash proceeds in the Euroclear or Clearstream participant’s account will be back-valued to the date on which settlement occurs in New York. DTC, Euroclear and Clearstream have agreed to the above procedures to facilitate transfers of interests in the Global Notes among participants in those settlement systems. However, the settlement systems are not obligated to perform these procedures and may discontinue or change these procedures at any time. Neither we nor the trustee will have any responsibility or liability for the performance by DTC, Euroclear or Clearstream or their participants or indirect participants of their obligations under the rules and procedures governing their operations, including maintaining, supervising or reviewing the records relating to, or payments made on account of, beneficial ownership interests in Global Notes.

Transfers between participants in DTC will be effected under DTC’s procedures and will be settled in same-day funds.

Certificated Notes

Notes in physical, certificated form will be issued and delivered to each person that DTC identifies as a beneficial owner of the related Notes only if:

In connection with any proposed exchange of a certificated Note for a Global Note, there shall be provided to the trustee, upon reasonable request therefore, all information necessary to allow the trustee to comply with any applicable tax reporting obligations, including without limitation any cost basis reporting obligations under Internal Revenue Code Section 6045. The trustee may rely on information provided to it and shall have no responsibility to verify or ensure the accuracy of such information.

S-29

MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS

The following discussion is a summary of the material U.S. federal income tax considerations that are likely to be relevant to the purchase, ownership and disposition of the Notes. This summary does not purport to be a comprehensive description of all of the tax considerations that may be relevant to a decision to purchase Notes by any particular investor. Thus, for example, this summary deals only with beneficial owners (referred to in this summary as “holders”) of Notes that hold their Notes as capital assets and acquired Notes upon their original issuance at their original issue price, which is the first price at which a substantial amount of the Notes is sold for money to the public (not including bond houses, brokers or similar persons or organizations acting in the capacity of underwriters, placement agents or wholesalers). Additionally, we have not described tax consequences that may be relevant to certain types of holders that are subject to special treatment under U.S. federal income tax laws, including:

Finally, this summary does not address other U.S. federal tax consequences (such as estate and gift tax consequences, the Medicare tax on net investment income and the alternative minimum tax, consequences arising under special timing rules prescribed under section 451(b) of the Code) or any state, local or non-U.S. tax consequences.

The discussion below is based upon the provisions of the Code, Treasury Regulations, rulings and judicial decisions as of the date hereof. Those authorities may be changed, perhaps retroactively, so as to result in U.S. federal income tax consequences different from those discussed below. This summary does not address all aspects of U.S. federal income taxes and does not deal with all tax consequences that may be relevant to holders in light of their personal circumstances.

For purposes of this discussion, the term “U.S. Holder” means a beneficial owner of a Note that is, for U.S. federal income tax purposes, an individual who is a citizen or resident of the United States or a domestic corporation, an estate the income of which is subject to United States federal income taxation regardless of its source, a trust if it (1) is subject to the primary supervision of a court within the United States and one or more United States persons have the authority to control all substantial decisions of the trust or (2) has a valid election in effect under applicable United States Treasury Regulations to be treated as a United States person. The term “non-U.S. Holder” means a beneficial owner of a Note that is not a U.S. Holder. If a partnership (including an

S-30

entity or arrangement treated as a partnership for U.S. federal income tax purposes) holds any Notes, the U.S. federal income tax treatment of a partner of the partnership generally will depend upon the status of the partner, the activities of the partnership and certain determinations made at the partner level. Partnerships holding Notes, and persons holding interests in such partnerships, should each consult their own tax advisors as to the consequences of investing in the Notes in their individual circumstances.

Consequences to U.S. Holders of Notes

Payments of Stated Interest

Stated interest on the Notes will generally be includible in the income of a U.S. Holder as ordinary income at the time the interest is received or accrued in accordance with the U.S. Holder’s method of accounting for U.S. federal income tax purposes. If the Notes are issued at more than a de minimis discount, a U.S. Holder will be required to include the difference in income as original issue discount in accordance with a “constant-yield method” before the receipt of cash attributable to such income, regardless of the U.S. Holder’s regular method of accounting for U.S. federal income tax purposes. A U.S. Holder is urged to consult its own tax advisor in the event the Notes are issued with original issue discount.

Sale, Exchange, Retirement or Other Taxable Disposition of Notes

A U.S. Holder will generally recognize taxable gain or loss upon the sale, exchange, retirement or other taxable disposition of a Note equal to the difference between the amount realized for the Note (less amounts attributable to accrued but unpaid stated interest, which will be taxable as a payment of such accrued interest) and the U.S. Holder’s tax basis in the Note. A U.S. Holder’s tax basis in a Note generally will be equal to the amount paid for the Note. Any gain or loss recognized on a taxable disposition of the Note will generally constitute capital gain or loss. A non-corporate U.S. Holder who has held the Note for more than one year generally will be eligible for reduced rates of taxation on long-term capital gain. The ability to deduct capital losses is limited.

Consequences to Non-U.S. Holders of Notes

Payments of Stated Interest

Subject to the discussion of backup withholding and FATCA below, a non-U.S. Holder will not be subject to U.S. federal withholding tax or income tax in respect of stated interest on the Notes provided that:

Sale, Exchange or Retirement of Notes

Subject to the discussion below under “Information Reporting and Backup Withholding,” a Non-U.S. Holder generally will not be subject to U.S. federal income tax on gain recognized on a sale, exchange or retirement of Notes.

S-31

Information Reporting and Backup Withholding.

Information returns will be filed with the IRS in connection with payments on the Notes made to, and the proceeds of dispositions of Notes effected by, certain U.S. taxpayers. In addition, certain U.S. taxpayers may be subject to backup withholding tax in respect of such payments if they do not provide their taxpayer identification numbers to the person from whom they receive payments and a certification that they are not subject to backup withholding or if they fail to report in full dividend and interest income. Non-U.S. taxpayers may be required to comply with applicable certification procedures to establish that they are not U.S. taxpayers in order to avoid the application of such information reporting requirements and backup withholding. Any amounts withheld under the backup withholding rules from a payment to a U.S. or Non-U.S. taxpayer generally would be allowed as a refund or a credit against such Holder’s U.S. federal income tax provided the required information is timely furnished to the IRS.

FATCA

Under certain circumstances, the Foreign Account Tax Compliance provisions of the United States Hiring Incentives to Restore Employment Act (“FATCA”) will impose a withholding tax of 30% on payments of interest on the Notes made to certain foreign entities unless various information reporting requirements are satisfied. Specifically, a 30% withholding tax may be imposed on interest on the Notes paid to a “foreign financial institution” or a “nonfinancial foreign entity” (each as defined in the Code), unless such entity is FATCA compliant. In order to be treated as FATCA compliant, an entity must provide certain documentation (usually an IRS Form W-8BEN or W-8BEN-E) containing information about its identity, its FATCA status, and if required, its direct and indirect U.S. owners. Accordingly, the entity through which the Notes are held will affect the determination of whether such withholding is required.

Under the applicable Treasury Regulations, withholding under FATCA generally applies to payments of interest on the Notes from their date of issuance. The FATCA withholding tax will apply to all withholdable payments without regard to whether the beneficial owner of the payment would otherwise be entitled to an exemption from imposition of withholding tax pursuant to an applicable tax treaty with the United States or U.S. domestic law. If payment of this withholding tax is made, holders that are otherwise eligible for an exemption from, or reduction of, U.S. federal withholding taxes with respect to such interest will be required to seek a credit or refund from the IRS to obtain the benefit of such exemption or reduction, if any. We will not pay additional amounts to holders of the Notes in respect of any amounts withheld. While withholding under FATCA would also have applied to payments of gross proceeds from the sale or other taxable disposition of the notes, proposed United States Treasury regulations (upon which taxpayers may rely until final regulations are issued) eliminate FATCA withholding on payments of gross proceeds entirely. Prospective holders should consult their own tax advisors regarding the potential application of withholding under FATCA to their investment in the Notes.

Investors should consult their own tax advisors with respect to the particular tax consequences of an investment in the Notes in their individual circumstances, including the possible effect of any pending legislation or proposed regulations.

S-32

UNDERWRITING

BofA Securities, Inc. is acting as representative of each of the underwriters named below. Subject to the terms and conditions set forth in an underwriting agreement among us and the underwriters, we have agreed to sell to the underwriters, and each of the underwriters has agreed, severally and not jointly, to purchase from us, the aggregate principal amount of Notes set forth opposite its name below.

Subject to the terms and conditions set forth in the underwriting agreement, the underwriters have agreed, severally and not jointly, to purchase all of the Notes sold under the underwriting agreement if any of these Notes are purchased. If an underwriter defaults, the underwriting agreement provides that the purchase commitments of the nondefaulting underwriters may be increased or the underwriting agreement may be terminated.

We have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended (the “Securities Act”), or to contribute to payments the underwriters may be required to make in respect of those liabilities.

The underwriters are offering the Notes, subject to prior sale, when, as and if issued to and accepted by them, subject to approval of legal matters by their counsel, including the validity of the Notes, and other conditions contained in the underwriting agreement, such as the receipt by the underwriters of officers’ certificates and legal opinions. The underwriters reserve the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part.

Commissions and Discounts

The following table shows the per Note and total underwriting discounts and commissions that we are to pay to the underwriters in connection with this offering.

The underwriters propose to offer some of the Notes to the public at the public offering price set forth on the cover page of this prospectus supplement, and some of the Notes to certain other Financial Industry Regulatory Authority, or FINRA, members at the public offering price less a concession not in excess of     % of the aggregate principal amount of the Notes. The underwriters may allow, and the dealers may reallow, a discount not in excess of     % of the aggregate principal amount of the Notes. After the initial offering of the Notes to the public, the public offering price and such concessions may be changed. No such change shall change the amount of proceeds to be received by us as set forth on the cover page of this prospectus supplement.

The expenses of the offering, not including the underwriting discount, are estimated at $                million and are payable by us.

No Sales of Similar Securities

Subject to certain exceptions, we have agreed not to directly or indirectly, offer, pledge, sell, contract to sell, grant any option for the sale of or otherwise transfer or dispose of any debt securities issued or guaranteed by us

S-33

or any securities convertible into or exercisable or exchangeable for debt securities issued or guaranteed by us or file any registration statement under the Securities Act with respect to any of the foregoing through the closing date without first obtaining the written consent of the representative. This consent may be given at any time without public notice.

Listing

The Notes are a new issue of securities with no established trading market. The Notes will not be listed on any securities exchange or quoted on any automated dealer quotation system.

We have been advised by certain of the underwriters that they currently intend to make a market in the Notes after completion of the offering as permitted by applicable laws and regulations. The underwriters are not obligated, however, to make a market in the Notes and any such market-making may be discontinued at any time in the sole discretion of the underwriters without any notice. Accordingly, no assurance can be given as to the liquidity of, or development of a public trading market for, the Notes. If an active public trading market for the Notes does not develop, the market price and liquidity of the Notes may be adversely affected.

Price Stabilization, Short Positions

In connection with the offering, the underwriters may purchase and sell Notes in the open market. These transactions may include over-allotment, covering transactions and stabilizing transactions. Over-allotment involves sales of Notes in excess of the aggregate principal amount of Notes to be purchased by the underwriters in the offering, which creates a short position for the underwriters. Covering transactions involve purchases of the Notes in the open market after the distribution has been completed in order to cover short positions. Stabilizing transactions consist of certain bids or purchases of Notes made for the purpose of preventing or retarding a decline in the market price of the Notes while the offering is in progress.

The underwriters also may impose a penalty bid. This occurs when a particular underwriter repays to the underwriters a portion of the underwriting discount received by it because the representative has repurchased Notes sold by or for the account of such underwriter in stabilizing or short covering transactions.

Any of these activities may cause the price of the Notes to be higher than the price that otherwise would exist in the open market in the absence of such transactions. These transactions may be effected in the over-the-counter market or otherwise and, if commenced, may be discontinued at any time without any notice relating thereto.

Neither we nor any of the underwriters make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price of the Notes. In addition, neither we nor any of the underwriters make any representation that the representative will engage in these transactions or that these transactions, once commenced, will not be discontinued without notice.

Other Relationships

The underwriters and their respective affiliates are full service financial institutions engaged in various activities, which may include sales and trading, commercial and investment banking, advisory, investment management, investment research, principal investment, hedging, market making, brokerage, valuation services and other financial and non-financial activities and services. Certain of the underwriters and their respective affiliates have provided, currently provide, and may in the future provide, a variety of these services to us and to persons and entities with relationships with us, for which they received or will receive customary fees and expenses. Certain of the underwriters and their affiliates were underwriters in connection with our IPO and our subsequent debt and equity offerings, for which they received customary fees. Additionally, affiliates of certain underwriters are lenders under the Revolving Credit Facility.

S-34

In the ordinary course of their various business activities, the underwriters and their respective affiliates, officers, directors and employees may purchase, sell or hold a broad array of investments and actively trade securities, derivatives, loans, commodities, currencies, credit default swaps and other financial instruments for their own account and for the accounts of their customers, and such investment and trading activities may involve or relate to our assets, securities or instruments (directly, as collateral securing other obligations or otherwise) or persons and entities with relationships with us. Certain of the underwriters and their affiliates that have a lending relationship with us routinely hedge their credit exposure to us consistent with their customary risk management policies. Typically, such underwriters and their affiliates would hedge such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities, including potentially the Notes. Any such credit default swaps or short positions could adversely affect future trading prices of the Notes. The underwriters and their respective affiliates may also communicate independent investment recommendations, market color or trading ideas or publish or express independent research views in respect of such assets, securities or instruments and may at any time hold, or recommend to clients that they should acquire, long or short positions in such assets, securities and instruments.

We intend to use the net proceeds of this offering to pay down a portion of the outstanding indebtedness under the Revolving Credit Facility. Affiliates of certain underwriters are lenders under the Revolving Credit Facility. Accordingly, affiliates of certain of the underwriters may receive more than 5% of the proceeds of this offering to the extent the proceeds are used to pay down a portion of the outstanding indebtedness under the Revolving Credit Facility.

Certain funds or accounts managed by affiliates of the Adviser may purchase Notes in the transaction through the underwriters at the public offering price.

Settlement

We expect that delivery of the Notes will be made to investors on or about                , 2024, which will be the                business day following the date hereof. Under Rule 15c6-1 under the Exchange Act, trades in the secondary market are required to settle in two business days, unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade Notes on the date hereof or the next succeeding two business days will be required by virtue of the fact that the Notes initially settle in T+                , to specify an alternate settlement arrangement at the time of any such trade to prevent a failed settlement. Purchasers of the Notes who wish to trade the Notes on the date hereof or the next succeeding                business days should consult their advisors.

Principal Business Addresses

The principal business address of BofA Securities, Inc. is One Bryant Park, New York, NY 10036. The principal business address of Goldman Sachs & Co. LLC is 200 West Street New York, NY 10282. The principal business address of J.P. Morgan Securities LLC is 383 Madison Avenue, New York, NY 10179. The principal business address of SMBC Nikko Securities America, Inc. is 277 Park Avenue, New York, NY 10172.

Other Jurisdictions

Other than in the United States, no action has been taken by us or the underwriters that would permit a public offering of the Notes offered by this prospectus supplement in any jurisdiction where action for that purpose is required. The Notes offered by this prospectus supplement may not be offered or sold, directly or indirectly, nor may this prospectus supplement or any other offering material or advertisements in connection with the offer and sale of any such securities be distributed or published in any jurisdiction, except under circumstances that will result in compliance with the applicable rules and regulations of that jurisdiction. Persons into whose possession this prospectus supplement comes are advised to inform themselves about and to observe any restrictions relating to the offering and the distribution of this prospectus supplement. This prospectus supplement does not constitute an offer to sell or a solicitation of an offer to buy any Notes offered by this prospectus supplement in any jurisdiction in which such an offer or a solicitation is unlawful.

S-35

ICBC Standard Bank Plc is restricted in its U.S. securities dealings under the United States Bank Holding Company Act and may not underwrite, subscribe, agree to purchase or procure purchasers to purchase Notes that are offered or sold in the United States. Accordingly, ICBC Standard Bank Plc shall not be obligated to, and shall not, underwrite, subscribe, agree to purchase or procure purchasers to purchase Notes that may be offered or sold by other underwriters in the United States. ICBC Standard Bank Plc shall offer and sell the Notes constituting part of its allotment solely outside the United States.

Notice to Prospective Investors in the European Economic Area

The Notes are not intended to be offered, sold or otherwise made available to and should not be offered, sold or otherwise made available to any retail investor in the European Economic Area (“EEA”). For these purposes, a retail investor means a person who is one (or more) of: (i) a retail client as defined in point (11) of Article 4(1) of Directive 2014/65/EU (as amended, “MiFID II”); (ii) a customer within the meaning of Directive (EU) 2016/97 (as amended, the “Insurance Distribution Directive”), where that customer would not qualify as a professional client as defined in point (10) of Article 4(1) of MiFID II; or (iii) not a qualified investor as defined in Regulation (EU) 2017/1129 (as amended, the “Prospectus Regulation”). Consequently no key information document required by Regulation (EU) No 1286/2014 (as amended, the “PRIIPs Regulation”) for offering or selling the Notes or otherwise making them available to retail investors in the EEA has been prepared and therefore offering or selling the Notes or otherwise making them available to any retail investor in the EEA may be unlawful under the PRIIPS Regulation. This prospectus supplement has been prepared on the basis that any offer of Notes in any Member State of the EEA will be made pursuant to an exemption under the Prospectus Regulation from the requirement to publish a prospectus for offers of Notes. This prospectus supplement is not a prospectus for the purposes of the Prospectus Regulation.

In connection with the offering, the underwriters are not acting for anyone other than the issuer and will not be responsible to anyone other than the issuer for providing the protections afforded to their clients nor for providing advice in relation to the offering.

The above selling restriction is in addition to any other selling restrictions set out below.

Notice to Prospective Investors in the United Kingdom

The Notes are not intended to be offered, sold or otherwise made available to and should not be offered, sold or otherwise made available to any retail investor in the United Kingdom (“UK”). For these purposes, a retail investor means a person who is one (or more) of (i) a retail client, as defined in point (8) of Article 2 of Regulation (EU) 2017/565 as it forms part of domestic law by virtue of the European Union (Withdrawal) Act 2018 (“EUWA”); or (ii) a customer within the meaning of the provisions of the Financial Services and Markets Act 2000 (as amended, the “FSMA”) and any rules or regulations made under the FSMA to implement Directive (EU) 2016/97, where that customer would not qualify as a professional client, as defined in point (8) of Article 2(1) of Regulation (EU) 600/2014 as it forms part of domestic law by virtue of the EUWA; or (iii) not a qualified investor as defined in Regulation (EU) 2017/1129 as it forms part of domestic law by virtue of the EUWA (the “UK Prospectus Regulation”). Consequently no key information document required by Regulation (EU) 1286/2014 as it forms part of domestic law by virtue of the EUWA (the “UK PRIIPs Regulation”) for offering or selling the Notes or otherwise making them available to retail investors in the UK has been prepared and therefore offering or selling the Notes or otherwise making them available to any retail investor in the UK may be unlawful under the UK PRIIPs Regulation. This prospectus supplement has been prepared on the basis that any offer of Notes in the UK will be made pursuant to an exemption under the UK Prospectus Regulation and the FSMA from the requirement to publish a prospectus for offers of Notes. This prospectus supplement is not a prospectus for the purposes of the UK Prospectus Regulation or the FSMA.

In connection with the offering, the underwriters are not acting for anyone other than the issuer and will not be responsible to anyone other than the issuer for providing the protections afforded to their clients nor for providing advice in relation to the offering.

S-36

This document is for distribution only to persons who (i) have professional experience in matters relating to investments and who qualify as investment professionals within the meaning of Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (as amended, the “Financial Promotion Order”), (ii) are persons falling within Article 49(2)(a) to (d) (“high net worth companies, unincorporated associations etc.”) of the Financial Promotion Order, (iii) are outside the United Kingdom, or (iv) are persons to whom an invitation or inducement to engage in investment activity (within the meaning of Section 21 of the Financial Services and Markets Act 2000, as amended (“FSMA”)) in connection with the issue or sale of any securities may otherwise lawfully be communicated or caused to be communicated (all such persons together being referred to as “relevant persons”). This document is directed only at relevant persons and must not be acted on or relied on by persons who are not relevant persons. Any investment or investment activity to which this document relates is available only to relevant persons and will be engaged in only with relevant persons.

Notice to Prospective Investors in the Dubai International Financial Centre

This prospectus supplement relates to an Exempt Offer in accordance with the Offered Securities Rules of the Dubai Financial Services Authority, or DFSA. This prospectus supplement is intended for distribution only to persons in the in the Dubai International Financial Centre, or DIFC of a type specified in the Offered Securities Rules of the DFSA. It must not be delivered to, or relied on by, any other person in the DIFC. The DFSA has no responsibility for reviewing or verifying any documents in connection with Exempt Offers. The DFSA has not approved this prospectus supplement nor taken steps to verify the information set forth herein and has no responsibility for the prospectus supplement. The Notes to which this prospectus supplement relates may be illiquid or subject to restrictions on their resale. Prospective purchasers of the Notes offered should conduct their own due diligence on the Notes. If you do not understand the contents of this prospectus supplement you should consult an authorized financial advisor.

Notice to Prospective Investors in Hong Kong

The Notes have not been offered or sold and will not be offered or sold in Hong Kong, by means of any document, other than (a) to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571 of the Laws of Hong Kong) (“Securities and Futures Ordinance”) and any rules made thereunder; or (b) in other circumstances which do not result in the document being a “prospectus” as defined in the Companies (Winding Up and Miscellaneous Provisions) Ordinance (Cap. 32 of the Laws of Hong Kong) (“Companies (Winding Up and Miscellaneous Provisions) Ordinance”) or which do not constitute an offer to the public within the meaning of the Companies (Winding Up and Miscellaneous Provisions) Ordinance. No advertisement, invitation or document relating to the Notes has been or may be issued or has been or may be in the possession of any person for the purposes of issue, whether in Hong Kong or elsewhere, which is directed at, or the contents of which are likely to be accessed or read by, the public of Hong Kong (except if permitted to do so under the securities laws of Hong Kong) other than with respect to Notes which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” as defined in the Securities and Futures Ordinance and any rules made thereunder.

Notice to Prospective Investors in Canada

This prospectus supplement constitutes an “exempt offering document” as defined in and for the purposes of applicable Canadian securities laws. No prospectus has been filed with any securities commission or similar regulatory authority in Canada in connection with the offer and sale of the Notes. No securities commission or similar regulatory authority in Canada has reviewed or in any way passed upon this prospectus supplement or on the merits of the Notes and any representation to the contrary is an offence.

Canadian investors are advised that this prospectus supplement has been prepared in reliance on section 3A.3 of National Instrument 33-105 Underwriting Conflicts (“NI 33-105”). Pursuant to section 3A.3 of NI 33-105, the Company and the underwriters in the offering are exempt from the requirement to

S-37

provide Canadian investors with certain conflicts of interest disclosure pertaining to “connected issuer” and/or “related issuer” relationships as would otherwise be required pursuant to subsection 2.1(1) of NI 33-105.

Resale Restrictions

The offer and sale of the Notes in Canada is being made on a private placement basis only and is exempt from the requirement that the company prepares and files a prospectus under applicable Canadian securities laws. Any resale of Notes by a Canadian investor in this offering must be made in accordance with applicable Canadian securities laws, which may vary depending on the relevant jurisdiction, and which may require resales to be made in accordance with Canadian prospectus requirements, a statutory exemption from the prospectus requirements, in a transaction exempt from the prospectus requirements or otherwise under a discretionary exemption from the prospectus requirements granted by the applicable local Canadian securities regulatory authority. These resale restrictions may under certain circumstances apply to resales of the Notes outside of Canada.

Representations of Purchasers

Each Canadian investor who purchases the Notes will be deemed to have represented to the Company, the underwriters and to each dealer from whom a purchase confirmation is received, as applicable, that the investor is (i) purchasing as principal, or is deemed to be purchasing as principal in accordance with applicable Canadian securities laws; (ii) an “accredited investor” as such term is defined in section 1.1 of National Instrument 45-106 Prospectus Exemptions or, in Ontario, as such term is defined in section 73.3(1) of the Securities Act (Ontario); and (iii) a “permitted client” as such term is defined in section 1.1 of National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations.

Taxation and Eligibility for Investment

Any discussion of taxation and related matters contained in this prospectus supplement does not purport to be a comprehensive description of all of the tax considerations that may be relevant to a Canadian investor when deciding to purchase the Notes and, in particular, does not address any Canadian tax considerations. No representation or warranty is hereby made as to the tax consequences to a resident, or deemed resident, of Canada of an investment in the Notes or with respect to the eligibility of the Notes for investment by such investor under relevant Canadian federal and provincial legislation and regulations.

Rights of Action for Damages or Rescission

Securities legislation in certain of the Canadian jurisdictions provides certain purchasers of securities pursuant to an offering memorandum (such as this prospectus supplement), including where the distribution involves an “eligible foreign security” as such term is defined in Ontario Securities Commission Rule 45-501 Ontario Prospectus and Registration Exemptions and in Multilateral Instrument 45-107 Listing Representation and Statutory Rights of Action Disclosure Exemptions, as applicable, with a remedy for damages or rescission, or both, in addition to any other rights they may have at law, where the offering memorandum, or other offering document that constitutes an offering memorandum, and any amendment thereto, contains a “misrepresentation” as defined under applicable Canadian securities laws. These remedies, or notice with respect to these remedies, must be exercised or delivered, as the case may be, by the purchaser within the time limits prescribed under, and are subject to limitations and defences under, applicable Canadian securities legislation. In addition, these remedies are in addition to and without derogation from any other right or remedy available at law to the investor.

S-38

Language of Documents

Upon receipt of this document, each Canadian investor hereby confirms that it has expressly requested that all documents evidencing or relating in any way to the sale of the securities described herein (including for greater certainty any purchase confirmation or any notice) be drawn up in the English language only. Par la réception de ce document, chaque investisseur canadien confirme par les présentes qu’il a expressément exigé que tous les documents faisant foi ou se rapportant de quelque manière que ce soit à la vente des valeurs mobilières décrites aux présentes (incluant, pour plus de certitude, toute confirmation d’achat ou tout avis) soient rédigés en anglais seulement.

S-39

LEGAL MATTERS

Certain legal matters in connection with the offering will be passed upon for us by Simpson Thacher & Bartlett LLP, Washington, D.C. In addition, Morris, Nichols, Arsht & Tunnell LLP will pass on certain legal matters for us. Certain legal matters in connection with the offering will be passed upon for the underwriters by Ropes & Gray LLP.

S-40

INFORMATION INCORPORATED BY REFERENCE

This prospectus supplement is part of a registration statement that we have filed with the SEC. Pursuant to the Small Business Credit Availability Act, we are allowed to “incorporate by reference” the information that we file with the SEC, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to comprise a part of this prospectus supplement from the date we file that document. Any reports filed by us with the SEC before the date that any offering of any securities by means of this prospectus supplement and the accompanying prospectus is terminated will automatically update and, where applicable, supersede any information contained in this prospectus supplement or incorporated by reference in this prospectus supplement. This prospectus supplement incorporates by reference the documents listed below:

We incorporate by reference into this prospectus supplement additional documents that we may file with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, or the Exchange Act, until all of the securities offered by this prospectus supplement and the accompanying prospectus have been sold or we otherwise terminate the offering of these securities; provided, however, the information “furnished” under Item 2.02 or Item 7.01 of Form 8-K or other information “furnished” to the SEC which is not deemed filed is not incorporated by reference in this prospectus supplement and any accompanying prospectus. Information that we file with the SEC will automatically update and may supersede information in this prospectus supplement, the accompanying prospectus and information previously filed with the SEC.

We will provide without charge to each person, including any beneficial owner, to whom a copy of this prospectus supplement is delivered, upon written request of any such person, a copy of any or all of the documents that has been or may be incorporated by reference into this prospectus supplement (excluding certain exhibits to the documents) at no cost. Any such request may be made by contacting us in writing at the following address:

Sixth Street Specialty Lending, Inc.

888 7th Avenue, 41st Floor

New York, NY 10106

Attention: TSLXInvestor Relations

Email: IRTSLX@sixthstreet.com.

You should rely only on the information incorporated by reference or provided in this prospectus supplement or accompanying prospectus. We have not authorized anyone to provide you with different or additional information, and you should not rely on such information if you receive it. We are not making an offer of or soliciting an offer to buy, any securities in any state or other jurisdiction where such offer or sale is not permitted. You should not assume that the information in this prospectus supplement or in the documents incorporated by reference is accurate as of any date other than the date on the front of this prospectus supplement or those documents.

S-41

PROSPECTUS

Sixth Street Specialty Lending, Inc.

Common Stock

Preferred Stock

Subscription Rights

Warrants

Debt Securities

We are a specialty finance company focused on lending to middle-market companies that has elected to be regulated as a business development company under the Investment Company Act of 1940. We seek to generate current income primarily in U.S.-domiciled middle-market companies through direct originations of senior secured loans and, to a lesser extent, originations of mezzanine and unsecured loans and investments in corporate bonds and equity securities. By “middle-market companies,” we mean companies that have annual EBITDA, which we believe is a useful proxy for cash flow, of $10 million to $250 million, although we may invest in larger or smaller companies on occasion As of September 30, 2023, our investment portfolio consisted of investments in 131 portfolio companies (including 42 structured credit investments, which include each series of collateralized loan obligation as a separate portfolio company investment) with an aggregate fair value of $3,113.3 million. We intend to continue to pursue an investment strategy focused primarily on direct origination of loans to middle-market companies domiciled in the United States.

We are an externally-managed, closed-end, non-diversified management investment company. Sixth Street Specialty Lending Advisers, LLC, or the Adviser, acts as our investment adviser and administrator. Our investment decisions are made by our Investment Review Committee, which includes senior personnel of our Adviser and Sixth Street Partners, LLC or “Sixth Street.” Sixth Street is a global investment business with over $60 billion of assets under management as of September 30, 2023.

The companies in our investment portfolio are typically highly leveraged, and, in many cases, our investments in these companies are not rated by any rating agency. If these investments were rated, we believe that most would likely receive a rating of below investment grade (that is, below BBB- or Baa3, which is often referred to as “junk”). Our exposure to below investment grade instruments involves certain risks, including speculation with respect to the borrower’s capacity to pay interest and repay principal. The debt investments in our portfolio generally have a significant portion of principal due at the maturity of the investment, which would result in a substantial loss to us if such borrowers are unable to refinance or repay their debt at maturity.

Substantially all of our debt investments have variable interest rates that reset periodically based on interest rate benchmarks such as the London Interbank Offered Rate, the Euro Interbank Offered Rate, the Secured Overnight Financing Rate, the Sterling Overnight Interbank Average Rate, the Federal Funds Effective Rate or the Prime Rate. As a result, significant increases in such interest rate benchmarks in the future would make it more difficult for these borrowers to service their obligations under the debt investments that we hold.

We may offer, from time to time, in one or more offerings or series, our common stock, preferred stock, debt securities, subscription rights to purchase shares of our common stock or warrants representing rights to purchase shares of our common stock, preferred stock or debt securities, which we refer to, collectively, as the “securities.” The preferred stock, debt securities, subscription rights and warrants offered hereby may be

convertible or exchangeable into shares of our common stock. The securities may be offered at prices and on terms to be described in one or more supplements to this prospectus.

In the event we offer common stock, the offering price per share of our common stock less any underwriting discounts or commissions will generally not be less than the net asset value per share of our common stock at the time we make the offering. However, we may issue shares of our common stock pursuant to this prospectus at a price per share that is less than our net asset value per share (i) in connection with a rights offering to our existing stockholders, (ii) with the prior approval of the majority of our outstanding voting securities or (iii) under such other circumstances as the Securities and Exchange Commission may permit.

The securities may be offered directly to one or more purchasers, or through agents designated from time to time by us or to or through underwriters or dealers. Each prospectus supplement relating to an offering will identify any agents or underwriters involved in the sale of the securities, and will disclose any applicable purchase price, fee, discount or commissions arrangement between us and our agents or underwriters or among our underwriters or the basis upon which such amount may be calculated. See “Plan of Distribution.” We will not sell any of the securities pursuant to this registration statement through agents, underwriters or dealers without delivery of this prospectus and a prospectus supplement describing the method and terms of the offering of such securities.

Our common stock is traded on the New York Stock Exchange, or NYSE, under the symbol “TSLX.” On December 20, 2023, the last reported sales price of our common stock on the NYSE was $21.08 per share. The net asset value per share of our common stock at September 30, 2023 (the last date prior to the date of this prospectus for which we reported net asset value) was $16.97.

Investing in our securities involves a high degree of risk. Shares of closed-end investment companies, including business development companies, frequently trade at a discount to their net asset values. If our shares trade at a discount to our net asset value, purchasers in any offering will face increased risk of loss. In addition, the companies in which we invest are subject to special risks. Before buying any securities, you should read the discussion of the material risks of investing in our securities, including the risk of leverage, in “Risk Factors “ beginning on page 24 of this prospectus and in the documents incorporated by reference herein.

This prospectus may not be used to consummate sales of our securities unless accompanied by a prospectus supplement.

Please read this prospectus and any accompanying prospectus supplements, including any information incorporated by reference herein or therein, before investing and keep such documents for future reference. This prospectus and any accompanying prospectus supplements, and the documents incorporated by reference herein or therein, contain important information about us that a prospective investor ought to know before investing in our securities. Information required to be included in a Statement of Additional Information may be found in this prospectus and an accompanying prospectus supplement, as applicable. We also file periodic and current reports, proxy statements and other information about us with the Securities and Exchange Commission. This information is available free of charge by contacting us at 888 7th Avenue, 41st Floor, New York, NY 10106, Attention: TSLX Investor Relations, by emailing us at IRTSLX@sixthstreet.com or visiting our website at https://sixthstreetspecialtylending.gcs-web.com/. Information on our website is not incorporated into or a part of this prospectus or any prospectus supplement. The Securities and Exchange Commission also maintains a website at http://www.sec.gov that contains this information.

The Securities and Exchange Commission has not approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is December 22, 2023

TABLE OF CONTENTS

We have not authorized any dealer, salesman or other person to give any information or to make any representation other than those contained in this prospectus, any prospectus supplement to this prospectus or any information that we have incorporated by reference herein or therein. This prospectus and any such supplements do not constitute an offer to sell or a solicitation of any offer to buy any security other than the registered securities to which they relate, nor do they constitute an offer to sell or a solicitation of an offer to buy any securities in any jurisdiction to any person to whom it is unlawful to make such an offer or solicitation in such jurisdiction. The information contained in this prospectus and any such supplements is accurate only as of the dates on their respective covers unless the information specifically indicates that another date applies. Our business, financial condition, results of operations and prospects may have changed since then. We will update these documents to reflect material changes only as required by law.

ABOUT THIS PROSPECTUS

This prospectus is part of an automatic shelf registration statement that we filed with the U.S. Securities and Exchange Commission, or SEC, as a “well-known seasoned issuer” as defined in Rule 405 under the Securities Act of 1933, as amended (the “Securities Act”). Under the shelf registration process, which constitutes a delayed offering in reliance on Rule 415 under the Securities Act, we may offer, from time to time, in one or more offerings of our common stock, preferred stock, debt securities, subscription rights to purchase shares of our common stock, or warrants representing rights to purchase shares of our common stock, preferred stock or debt securities, on terms to be determined at the time of the offering.

i

The securities may be offered at prices and on terms described in one or more supplements to this prospectus. This prospectus provides you with a general description of the offerings of securities that we may conduct pursuant to this prospectus. Each time we use this prospectus to sell securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering. A prospectus supplement may also add, update or change information contained in this prospectus.

Please read this prospectus and the accompanying prospectus supplement, including any information incorporated herein or therein by reference, before you make an investment decision. You should also read the documents we have referred you to in “Available Information” and “Information Incorporated by Reference” below for information on our company and our consolidated financial statements.

ii

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

FINANCIAL HIGHLIGHTS

The financial data set forth in the following table as of and for the years ended December 31, 2022, 2021, 2020, 2019, 2018, 2017, 2016, 2015, 2014 and 2013 are derived from our consolidated financial statements, which have been audited by KPMG LLP, an independent registered public accounting firm whose reports thereon are incorporated by reference in this prospectus, certain documents incorporated by reference in this prospectus or the accompanying prospectus supplement, or our Annual Reports on Form 10-K filed with the SEC, which may be obtained from www.sec.gov or upon request. The financial data set forth in the following table as of and for the nine months ended September 30, 2023, is derived from our unaudited financial statements, but in the opinion of management, reflects all adjustments (consisting only of normal recurring adjustments) that are necessary to present fairly the results of such interim period. Interim results as of and for the nine months ended September 30, 2023, are not necessarily indicative of the results that may be expected for the year ending December 31, 2023. You should read these financial highlights in conjunction with our consolidated financial statements and notes thereto and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” incorporated by reference into this prospectus, any documents incorporated by reference in this prospectus or the accompanying prospectus supplement, or our Annual Reports on Form 10-K filed with the SEC.

22

23

RISK FACTORS

Investing in our securities involves a number of significant risks. You should carefully consider the risks set out below and described in Part I, Item 1A, “Risk Factors,” in our 2022 Annual Report and Part I, Item IA, “Risk Factors,” in our quarterly report on Form 10-Q for the three months ended March 31, 2023 (the “1Q 2023 Quarterly Report”), in our quarterly report on Form 10-Q for the three months ended June 30, 2023 (the “2Q 2023 Quarterly Report”), and in our 3Q 2023 Quarterly Report, which are incorporated by reference in this prospectus, together with the other information set forth in this prospectus or in any prospectus supplement and in the other documents that we include or incorporate by reference into this prospectus before making a decision about investing in our securities. The risks and uncertainties set out below and discussed in our 2022 Annual Report, 1Q 2023 Quarterly Report, 2Q 2023 Quarterly Report, and 3Q 2023 Quarterly Report are not the only ones we face. Additional risks and uncertainties not presently known to us or not presently deemed material by us may also materially and adversely affect our business, financial condition and results of operations. In such case, our net asset value and the trading price of our securities could decline, and you may lose all or part of your investment.

Risks Related to Offerings Pursuant to This Prospectus

We will have broad discretion over the use of proceeds of any offering made pursuant to this prospectus, to the extent it is successful.

We will have significant flexibility in applying the proceeds of any offering made pursuant to this prospectus. For example, we may pay operating expenses from net proceeds, which could limit our ability to achieve our investment objective.

The net asset value per share of our common stock may be diluted if we sell or otherwise issue shares of our common stock at prices below the then-current net asset value per share of our common stock.

Pursuant to approval granted at a special meeting of stockholders held on May 25, 2023, we are currently permitted to sell or otherwise issue shares of our common stock at a price below our then-current net asset value per share, subject to the approval of our Board and certain other conditions. Such stockholder approval expires on May 25, 2024. We intend to propose the extension of this approval in future years.

Any decision to sell or otherwise issue shares of our common stock below our then-current net asset value per share would be subject to the determination by our board of directors that such issuance or sale is in our and our stockholders’ best interests.

If we were to sell or otherwise issue shares of our common stock below our then-current net asset value per share, such issuances or sales would result in an immediate dilution to the net asset value per share of our common stock. This dilution would occur as a result of the issuance or sale of shares at a price below the then-current net asset value per share of our common stock and a proportionately greater decrease in the stockholders’ interest in our earnings and assets and their voting interest in us than the increase in our assets resulting from such issuance or sale. Because the number of shares of common stock that could be so issued and the timing of any issuance is not currently known, the actual dilutive effect cannot be predicted.

Further, if our current stockholders do not purchase any shares to maintain their percentage interest, regardless of whether such offering is above or below the then-current net asset value per share, their voting power will be diluted. For additional information and hypothetical examples of these risks, see “Sales of Common Stock Below Net Asset Value” and the prospectus supplement pursuant to which such sale is made.

24

Your interest in us may be diluted if you do not fully exercise your subscription rights in any rights offering. In addition, if the subscription price is less than our net asset value per share, then you will experience an immediate dilution of the aggregate net asset value of your shares.

In the event we issue subscription rights, stockholders who do not fully exercise their subscription rights should expect that they will, at the completion of a rights offering pursuant to this prospectus, own a smaller proportional interest in us than would otherwise be the case if they fully exercised their rights. We cannot state precisely the amount of any such dilution in share ownership because we do not know at this time what proportion of the shares will be purchased as a result of such rights offering.

In addition, if the subscription price is less than the net asset value per share of our common stock, then our stockholders would experience an immediate dilution of the aggregate net asset value of their shares as a result of the offering. The amount of any decrease in net asset value is not predictable because it is not known at this time what the subscription price and net asset value per share will be on the expiration date of a rights offering or what proportion of the shares will be purchased as a result of such rights offering. Such dilution could be substantial.

We may in the future determine to issue preferred stock, which could adversely affect the market value of our common stock and cause the net asset value and market value of our common stock to be more volatile.

The issuance of shares of preferred stock with dividend or conversion rights, liquidation preferences or other economic terms favorable to the holders of preferred stock could adversely affect the market price for our common stock by making an investment in the common stock less attractive and could make the net asset value and market value of our common stock more volatile. Payment of dividends and repayment of the liquidation preference of preferred stock would take preference over any dividends or other payments to our common stockholders, and holders of preferred stock would not be subject to any of our expenses or losses and would not be entitled to participate in any income or appreciation in excess of their stated preference (other than convertible preferred stock that converts into common stock). If the dividend rate on the preferred stock were to approach the net rate of return on our investment portfolio, the benefit of leverage to the holders of the common stock would be reduced. If the dividend rate on the preferred stock were to exceed the net rate of return on our portfolio, the leverage would result in a lower rate of return to the holders of common stock than if we had not issued preferred stock. Any decline in the net asset value of our investments would be borne entirely by the holders of common stock. Therefore, if the market value of our portfolio were to decline, the leverage would result in a greater decrease in net asset value to the holders of common stock than if we were not leveraged through the issuance of preferred stock. This greater net asset value decrease would also tend to cause a greater decline in the market price for the common stock. We might be in danger of failing to maintain the required asset coverage of the preferred stock or of losing our ratings on the preferred stock or, in an extreme case, our current investment income might not be sufficient to meet the dividend requirements on the preferred stock. In order to counteract such an event, we might need to liquidate investments in order to fund a redemption of some or all of the preferred stock. In addition, under the 1940 Act, preferred stock constitutes a “senior security” for purposes of the asset coverage test.

Holders of any preferred stock we might issue would have the right to elect members of the board of directors and class voting rights on certain matters.

Holders of any preferred stock we might issue, voting separately as a single class, would have the right to elect two members of the Board at all times and in the event dividends become two full years in arrears would have the right to elect a majority of the directors until such arrearage is completely eliminated. In addition, preferred stockholders may have class voting rights on certain matters, including changes in fundamental investment restrictions and conversion to open-end status, and, accordingly, could veto any such changes. Restrictions imposed on the declarations and payment of dividends or other distributions to the holders of our common stock and preferred stock, both by the 1940 Act and by requirements imposed by rating agencies or the terms of our credit facilities, might impair our ability to maintain our qualification as a RIC for federal income

25

tax purposes. While we would intend to redeem our preferred stock to the extent necessary to enable us to distribute our income as required to maintain our qualification as a RIC, there can be no assurance that such actions could be effected in time to meet the tax requirements.

26

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus contains forward-looking statements that involve substantial risks and uncertainties. These forward-looking statements are not historical facts, but rather are based on current expectations, estimates and projections about us, our current and prospective portfolio investments, our industry, our beliefs, and our assumptions. Words such as “anticipates,” “expects,” “intends,” “plans,” “believes,” “seeks,” “estimates,” “would,” “should,” “targets,” “projects,” and variations of these words and similar expressions are intended to identify forward-looking statements. These statements are not guarantees of future performance and are subject to risks, uncertainties, and other factors, some of which are beyond our control and difficult to predict, that could cause actual results to differ materially from those expressed or forecasted in the forward-looking statements.

In addition to factors identified elsewhere in this prospectus and the documents incorporated by reference herein, the following factors, among others, could cause actual results to differ materially from forward-looking statements or historical performance:

Although we believe that the assumptions on which these forward-looking statements are based are reasonable, some of those assumptions are based on the work of third parties and any of those assumptions could prove to be inaccurate; as a result, forward-looking statements based on those assumptions also could prove to be inaccurate. In light of these and other uncertainties, the inclusion of a projection or forward-looking statement in this prospectus should not be regarded as a representation by us that our plans and objectives will be achieved. These risks and uncertainties include, among other things, those described or identified in the section entitled “Risk Factors” in this prospectus and in Part I, Item 1A and Part II, Item 1A of our 3Q 2023 Quarterly Report, and in our 2022 Annual Report and those discussed in other documents we file with the SEC and elsewhere in this prospectus and the documents incorporated by reference herein. You should not place undue reliance on these forward-looking statements, which apply only as of the date of this prospectus. We do not undertake any obligation to update or revise any forward-looking statements or any other information contained herein or therein, except as required by applicable law. You should understand that, under Section 27A(b)(2)(B) of the Securities Act and Section 21E(b)(2)(B) of the Exchange Act, the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, which preclude civil liability for certain forward-looking statements, do not apply to the forward-looking statements made in connection with any offering of securities pursuant to this prospectus.

The “TSLX” and “TAO” marks are marks of Sixth Street.

27

USE OF PROCEEDS

Unless otherwise specified in a prospectus supplement, we intend to use the net proceeds from the sale of our securities pursuant to this prospectus for general corporate purposes, which may include investing in portfolio companies in accordance with our investment objective and strategies described in this prospectus and repaying indebtedness (which will be subject to reborrowing). The supplement to this prospectus relating to an offering will more fully identify the use of the proceeds from such offering.

We estimate that it will take less than three months for us to substantially invest the net proceeds of any offering made pursuant to this prospectus, depending on the availability of attractive opportunities, market conditions and the amount raised.

Proceeds not immediately used for new investments or the temporary repayment of debt will be invested primarily in cash, cash equivalents, U.S. government securities and other high-quality investments that mature in one year or less from the date of investment. These securities may have lower yields than the types of investments we would typically make in accordance with our investment objective and, accordingly, may result in lower dividends, if any, during such period.

28

PRICE RANGE OF COMMON STOCK AND DISTRIBUTIONS

Our common stock is traded on the NYSE under the symbol “TSLX.” Our common stock has historically traded at prices both above and below our net asset value per share. It is not possible to predict whether our common stock will trade at a price per share at, above or below net asset value per share. See “Risk Factors—Risks Related to Offerings Pursuant to This Prospectus.”

The following table sets forth the net asset value per share of our common stock, the range of high and low closing sales prices of our common stock reported on the NYSE, the closing sales price as a premium (discount) to net asset value and the dividends declared by us in each fiscal quarter for the year ending December 31, 2023, and for the years ended December 31, 2022 and December 31, 2021. On December 20, 2023, the last reported closing sales price of our common stock on the NYSE was $21.08 per share, which represented a premium of approximately 24.2% to the net asset value per share reported by us as of September 30, 2023, the last date prior to the date of this prospectus for which we reported net asset value.

To the extent we have earnings available for distribution, we expect to continue distributing quarterly dividends to our stockholders. Our quarterly dividends, if any, will be determined by our Board. Any dividends to our stockholders will be declared out of assets legally available for distribution.

29

The following tables summarize dividends declared during the nine months ended September 30, 2023 and years ended December 31, 2022 and 2021:

The dividends declared during the nine months ended September 30, 2023 were derived from net investment income, determined on a tax basis. The dividends declared during the year ended December 31, 2022 were derived from net investment income and net realized capital gains, determined on a tax basis.

To the extent that the amounts distributed by us are in excess of our current and accumulated earnings and profits, such excess distributions will be treated first as a return of capital to the extent of a stockholder’s tax basis in his or her shares and then as capital gain. Reducing a stockholder’s tax basis will have the effect of increasing his or her gain (or reducing loss) on a subsequent sale of shares. The specific tax characteristics of the dividend will be reported to stockholders after the end of the calendar year.

To be treated as a regulated investment company, or a RIC, for U.S. federal income tax purposes and therefore to avoid being subject to corporate-level U.S. federal income taxation of our earnings, we must

30

distribute (or be treated as distributing) in each taxable year dividends for tax purposes equal to at least 90% of our investment company taxable income (as defined by the Code) and 90% of our net tax-exempt income to our stockholders in that taxable year. In addition, we generally will be subject to a nondeductible U.S. federal excise tax equal to 4% of the amount by which our distributions for a calendar year are less than the sum of:

For these purposes, we will be deemed to have distributed any net ordinary taxable income or capital gain net income on which we have paid U.S. federal income tax. Depending on the level of taxable income earned in a calendar year, we may choose to carry forward taxable income for distribution in the following calendar year, and pay any applicable U.S. federal excise tax. We elected to retain a portion of income and capital gains for the nine months ended September 30, 2023 and for calendar years ended December 31, 2022 and 2021 for purposes of additional liquidity and we recorded a net expense of $1.8 million for the nine months ended September 30, 2023 and $2.2 million and $0.7 million for the years ended December 31, 2022, and December 31, 2021, respectively, for U.S. federal excise tax as a result. We cannot assure you that we will achieve results that will permit the payment of any dividends. See “Risk Factors—Risks Related to Our Business and Structure—We will be subject to corporate-level U.S. federal income tax if we are unable to maintain our qualification as a RIC under Subchapter M of the Code, including as a result of our failure to satisfy the RIC distribution requirements” in Part I, Item 1A of our 2022 Annual Report.

We also intend to distribute net capital gains (that is, net long-term capital gains in excess of net short-term capital losses), if any, at least annually out of the assets legally available for such distributions. However, we may decide in the future to retain such net capital gains for investment and elect to treat such gains as deemed distributions to our stockholders. If this happens, our stockholders will be treated for U.S. federal income tax purposes as if they had received an actual distribution of the net capital gains that we retain and they reinvested the net after-tax proceeds in us. In this situation, our stockholders would be eligible to claim a tax credit (or, in certain circumstances, a tax refund) equal to their allocable share of the tax we paid on the capital gains deemed distributed to them. See “Material U.S. Federal Income Tax Considerations.” We cannot assure you that we will achieve results that will permit us to pay any cash dividends or that we will not be limited in our ability to pay dividends under the asset coverage test applicable to us under the 1940 Act.

Unless our common stockholders elect to receive their dividends in cash, we intend to make such distributions in additional shares of our common stock under our dividend reinvestment plan. See “Dividend Reinvestment Plan.”

31

SENIOR SECURITIES

Information about our senior securities is shown as of the dates indicated in the below table. The report of our independent registered public accounting firm, KPMG LLP, on the senior securities table as of December 31, 2022 is included in our 2022 Annual Report and is incorporated by reference to the registration statement of which this prospectus is a part.