Filed Pursuant to Rule 497
Registration No. 333-231271

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.

Subject to Completion

Preliminary Prospectus Supplement dated October 25, 2019

PROSPECTUS SUPPLEMENT

(To Prospectus dated May 7, 2019)

$            

            % 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                 , 2020. 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 June 30, 2019, our investment portfolio consisted of investments in 56 portfolio companies with an aggregate fair value of $2,060.5 million. We intend to continue to pursue an investment strategy focused on direct origination of loans to middle-market companies principally domiciled in the United States.

We are an externally managed, closed-end, non-diversified management investment company. TSL Advisers, LLC, or the Adviser, acts as our investment adviser and administrator. We and the Adviser are part of the TPG Sixth Street Partners platform, which had over $32 billion of assets under management as of June 30, 2019. TPG Sixth Street Partners is a global finance and investment firm in a strategic partnership with TPG, the global alternative asset firm.

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 Canadian Dollar Offered Rate, the Bank Bill Swap Bid Rate, the Euro Interbank Offered 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.

Investing in the Notes involves risks, including the risk of leverage, that are described in the “Risk Factors” section beginning on page S-10 of this prospectus supplement and page 23 of the accompanying prospectus and in the documents incorporated by reference herein and therein.

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. This information is available free of charge by contacting us at 888 7th Avenue, 35th Floor, New York, NY 10106, Attention: TSLX Investor Relations, by emailing us at IRTSL@tpg.com or visiting our website at http://www.tpgspecialtylending.com. Information on our website is not incorporated into or a part of this prospectus supplement or the accompanying prospectus. The Securities and Exchange Commission 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 Securities and Exchange Commission 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                 , 2019.

Joint Book-Running Managers

The date of this prospectus supplement is                 , 2019.

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

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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:

TPG Specialty Lending, Inc.

888 7th Avenue, 35th Floor

New York, NY 10106

Attention: TSLX Investor Relations

Email: IRTSL@tpg.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.

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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 2018 Annual Report and Part II, Item 1A of our 2019 Q1 Quarterly Report and 2019 Q2 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.

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THE COMPANY

This summary highlights some of the information contained elsewhere or incorporated by reference in this prospectus supplement and the accompanying prospectus. It is not complete and may not contain all of the information that you may want to consider. You should read this entire prospectus supplement, the accompanying prospectus, any free writing prospectus relating to this offering and the documents incorporated by reference in this prospectus supplement and the accompanying prospectus carefully. In particular, you should read the more detailed information set forth under “Risk Factors” in this prospectus supplement and the accompanying prospectus and the consolidated financial statements and the related notes included elsewhere or incorporated by reference in this prospectus supplement and the accompanying prospectus.

As used in the prospectus supplement and the accompanying prospectus, except where the context suggests otherwise, references to:

We have elected to be regulated as a business development company, or BDC, under the Investment Company Act of 1940, as amended, or the 1940 Act. In addition, for U.S. federal income tax purposes we have elected to be treated as a regulated investment company, or RIC, under the Internal Revenue Code of 1986, as amended, or the Code.

TPG Specialty Lending

We are a specialty finance company focused on lending to middle-market companies. Since we began our investment activities in July 2011, through June 30, 2019, we have originated more than $11.2 billion aggregate principal amount of investments and retained approximately $5.7 billion aggregate principal amount of these investments on our balance sheet prior to any subsequent exits and repayments. 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 earnings before interest, income taxes, depreciation and amortization, or 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 June 30, 2019, our core portfolio companies, which excludes certain investments that fall outside of our typical borrower profile and represent 79.1% of our total investments based on fair value, had weighted average annual revenue of $107.8 million and weighted average annual EBITDA of $32.6 million.

We generate revenues primarily in the form of interest income from the investments we hold. In addition, we may generate income from dividends on direct equity investments, capital gains on the sale of investments and various loan origination and other fees.

We have operated as a BDC since we began our investment activities in July 2011, and we are currently one of the largest BDCs by total assets. In conducting our investment activities, we believe that we benefit from the significant scale and resources of our Adviser and its affiliates.

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Investment Portfolio

The companies in which we invest use our capital to support organic growth, acquisitions, market or product expansion and recapitalizations (including restructurings).

We invest in first-lien debt, second-lien debt, mezzanine and unsecured debt and equity and other investments. Our first-lien debt may include stand-alone first-lien loans; “last out” first-lien loans, which are loans that have a secondary priority behind super-senior “first out” first-lien loans; “unitranche” loans, which are loans that combine features of first-lien, second-lien and mezzanine debt, generally in a first-lien position; and secured corporate bonds with similar features to these categories of first-lien loans. Our second-lien debt may include secured loans, and, to a lesser extent, secured corporate bonds, with a secondary priority behind first-lien debt.

As of June 30, 2019, our portfolio based on fair value consisted of 97.3% first-lien debt investments, 0.3% second-lien debt investments, 0.1% mezzanine debt investments, and 2.3% equity and other investments. As of June 30, 2019, 99.4% of our debt investments based on fair value bore interest at floating rates (when including investment specific hedges), with 94.7% of these subject to interest rate floors, which we believe helps act as a portfolio-wide hedge against inflation.

As of June 30, 2019 and December 31, 2018, we had investments in 56 and 46 portfolio companies, respectively, with an aggregate fair value of $2,060.5 million and $1,706.0 million, respectively.

For the three months ended June 30, 2019, the principal amount of new investments funded was $344.0 million in 12 new portfolio companies and two existing portfolio companies. For this period, we had $128.1 million aggregate principal amount in exits and repayments.

For the year ended December 31, 2018, the principal amount of new investments funded was $816.9 million in 19 new portfolio companies and 14 existing portfolio companies. For this period, we had $790.3 million aggregate principal amount in exits and repayments.

As of June 30, 2019, the largest single investment based on fair value represented 4.2% of our total investment portfolio. As of June 30, 2019, the average investment size in each of our portfolio companies was approximately $36.8 million based on fair value. As of June 30, 2019, the largest industry represented 19.8% of our total investment portfolio based on fair value.

Since we began investing in 2011 through June 30, 2019, weighted by capital invested, our exited investments have generated an average realized gross internal rate of return to us of 18.7% (based on total capital invested of $3.6 billion and total proceeds from these exited investments of $4.4 billion). Eighty nine percent of these exited investments resulted in a realized gross internal rate of return to us of 10% or greater. For a description of how we calculate gross internal rates of return, see “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Results of Operations—Realized Gross Internal Rate of Return” in Part I, Item 2 of our 2019 Q2 Quarterly Report, which is incorporated herein by reference.

Corporate Structure

TPG Specialty Lending, Inc. is a Delaware corporation formed on July 21, 2010. TSL Advisers, LLC is our external manager.

Our portfolio is subject to diversification and other requirements because we elected to be regulated as a BDC under the 1940 Act and treated as a RIC for U.S. federal income tax purposes. We made our BDC election on April 15, 2011. We intend to maintain these elections. See “Regulation as a Business Development Company” in Part I, Item 1 of our 2018 Annual Report, which is incorporated by reference in the accompanying prospectus, for more information on these requirements.

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About Our Adviser

Our Adviser is a Delaware limited liability company. Our Adviser acts as our investment adviser and administrator and is a registered investment adviser with the SEC under the Investment Advisers Act of 1940, as amended, or the Advisers Act.

Our Adviser sources and manages our portfolio through our Investment Team, a dedicated team of investment professionals predominately focused on us. Our Investment Team is led by our Chairman and Chief Executive Officer and our Adviser’s Co-Chief Investment Officer Joshua Easterly and our Adviser’s Co-Chief Investment Officer Alan Waxman, both of whom have substantial experience in credit origination, underwriting and asset management. Our investment decisions are made by our Investment Review Committee, which includes senior personnel of our Adviser and TSSP. The members of our Investment Review Committee are Joshua Easterly, Michael Fishman, Alan Waxman, Robert “Bo” Stanley and David Stiepleman.

TSSP is a global finance and investment firm with over $32 billion of assets under management as of June 30, 2019. TSSP is in a strategic partnership with TPG, the global alternative asset firm. TSSP’s core platforms include TPG Specialty Lending, TSL Europe, which is aimed at European middle-market loan originations, TSSP Adjacent Opportunities, which has the flexibility to invest across all of TSSP’s private credit market investments, TSSP Opportunities Partners, which focuses on actively managed opportunistic investments across the credit cycle, TPG Institutional Credit Partners, which is a “public-side” credit investment platform focused on investment opportunities in broadly syndicated leveraged loan markets, and TSSP Capital Solutions, which provides financing solutions to growing companies. TSSP has a long-term oriented, highly flexible capital base that allows it to invest across industries, geographies, capital structures and asset classes. TSSP has extensive experience with highly complex, global public and private investments executed through primary originations, secondary market purchases and restructurings, and has a team of over 225 investment and operating professionals. As of June 30, 2019, thirty three (33) of these personnel are dedicated to our business, including twenty five (25) investment professionals.

Our Adviser consults with TSSP in connection with a substantial number of our investments. The TSSP platform provides us with a breadth of large and scalable investment resources. We believe we benefit from TSSP’s market expertise, insights into industry, sector and macroeconomic trends and intensive due diligence capabilities, which help us discern market conditions that vary across industries and credit cycles, identify favorable investment opportunities and manage our portfolio of investments.

Recent Developments

In connection with this offering, we intend to enter into interest rate swaps to better align the interest rates of our liabilities with our investment portfolio, which consists of predominately floating rate loans.

Corporate Information

Our principal executive offices are located at 301 Commerce Street, Suite 3300, Fort Worth, TX 76102 and our telephone number is (817) 871-4000. Our corporate website is located at http://www.tpgspecialtylending.com. Information on our website is not incorporated into or a part of this prospectus supplement or the accompanying prospectus.

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SPECIFIC TERMS OF THE NOTES AND THE OFFERING

This prospectus supplement sets forth certain terms of the Notes that we are offering pursuant to this prospectus supplement and supplements the accompanying prospectus that is attached to the back of this prospectus supplement. This section outlines certain legal and financial terms of the Notes. You should read this section together with the more detailed description of the Notes under the heading “Description of Notes” in this prospectus supplement and in the accompanying prospectus under the heading “Description of Our Debt Securities” before investing in the Notes. Capitalized terms used in this prospectus supplement and not otherwise defined shall have the meanings ascribed to them in the accompanying prospectus or in the indenture governing the Notes, as amended from time to time, the “indenture”.

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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 2018 Annual Report and Part 1, Item IA, “Risk Factors,” in our 2019 Q1 Quarterly Report and our 2019 Q2 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 2018 Annual Report and our 2019 Q1 Quarterly Report and 2019 Q2 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 This Offering

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

The Notes will not be secured by any of our assets or any of the assets of our subsidiaries. As a result, the Notes will be 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, 2019, we had approximately $481.2 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 will be 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 will be 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.

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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, 2019 our total consolidated indebtedness was approximately $918.7 million aggregate principal amount outstanding, of which approximately $481.2 million was secured indebtedness at the TSLX level and none of which was indebtedness of our subsidiaries, and approximately $437.5 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 will be rated by Moody’s Investor Service, or Moody’s, S&P Global Ratings, or S&P, and Fitch Ratings, or Fitch. There can be no assurance that their respective credit ratings will remain for any given

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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 will contain limited protection for holders of the Notes.

The indenture 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 will 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.

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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 Convertible Notes or 2023 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, Convertible Notes and 2023 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 Convertible Notes and 2023 Notes each contain a provision that would require us to offer to purchase the respective Convertible Notes or 2023 Notes upon the occurrence of a fundamental change. Any

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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.”

If an active trading market does not develop for the Notes, you may not be able to resell them.

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 after the offering, 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 develop 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 does not develop, 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.

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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, 2019, we had $481.2 million outstanding under the Revolving Credit Facility. 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. As of September 30, 2019, amounts outstanding under our Revolving Credit Facility bore interest at a rate of LIBOR, Euribor, CDOR or BBSY plus a margin of 1.875%. The stated maturity date of the Revolving Credit Facility is February 14, 2024. See “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Financial Condition, Liquidity and Capital Resources—Revolving Credit Facility” in our 2019 Q2 Quarterly Report, which is incorporated herein by reference.

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.

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SENIOR SECURITIES

Information about our senior securities is shown in the following table as of the end of each fiscal year ended December 31 since we commenced operations and as of June 30, 2019. The report of our independent registered public accounting firm, KPMG LLP, on the senior securities table as of December 31, 2018 is attached as an exhibit to the registration statement of which this prospectus supplement and the accompanying prospectus are a part. This information about our senior securities should be read in conjunction with our consolidated financial statements and related notes thereto and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” included in our 2018 Annual Report and our 2019 Q2 Quarterly Report.

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CAPITALIZATION

The following table sets forth our consolidated capitalization at June 30, 2019. You should read this table together with “Use of Proceeds” described in this prospectus supplement and our most recent balance sheet included elsewhere in this prospectus supplement or the accompanying prospectus, or incorporated by reference herein or therein.

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MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The information in the Management’s Discussion and Analysis of Financial Condition and Results of Operations in our 2019 Q2 Quarterly Report is incorporated herein by reference.

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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 January 22, 2018, between us and Wells Fargo Bank, National Association, as trustee (the “trustee”), as supplemented by a separate supplemental indenture to be dated as of the settlement date for the Notes (the “second supplemental indenture”). As used in this section, all references to the indenture mean the base indenture as supplemented by the second 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.

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We may, without the consent of the holders, issue 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 offered hereby 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 no more than a de minimis amount of original issue discount, or otherwise be part of the same issue as the Notes offered hereby 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 will bear cash interest at a rate of     % per year until maturity. Interest on the Notes will accrue from                 , 2019 or from the most recent date on which interest has been paid or duly provided for. Interest will be payable semiannually in arrears on                  and                 of each year, beginning on                 , 2020.

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.

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Ranking

The Notes will be our direct, general unsecured obligations that will rank:

As of September 30, 2019, our total consolidated indebtedness was approximately $918.7 million aggregate principal amount outstanding, of which approximately $481.2 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, 2019. 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

We may redeem some or all of the Notes at any time, or from time to time. If we choose to redeem any Notes prior to maturity, we will pay a redemption price equal to the greater of the following amounts, plus, in each case, accrued and unpaid interest to the redemption date:

provided, however, that if we redeem any Notes on or after                 ,                (the date falling                 prior to the maturity date of the Notes), the redemption price for the Notes will be equal to 100% of the principal amount of the Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the date of redemption. Calculation of the redemption price will be made by us or on our behalf by such person as we shall designate; provided that such calculation or the correctness thereof shall not be a duty or obligation of the trustee.

If we choose to redeem any Notes, we will deliver a notice of redemption to holders of Notes not less than 30 nor more than 60 days before the redemption date. Any exercise of our option to redeem the Notes will be

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done in compliance with the 1940 Act. If we are redeeming less than all of the Notes, the particular Notes to be redeemed will be selected by the trustee in accordance with the applicable procedures of DTC and in accordance with the 1940 Act; provided, however, that no such partial redemption shall reduce the portion of the principal amount of a Note not redeemed to less than $2,000. 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 of the Notes called for redemption.

For purposes of calculating the redemption price in connection with the redemption of the Notes, on any redemption date, the following terms have the meanings set forth below:

“Treasury Rate” means, with respect to any redemption date, the rate per annum equal to the semi-annual equivalent yield-to-maturity of the Comparable Treasury Issue (computed as of the third business day immediately preceding the redemption), assuming a price for the Comparable Treasury Issue (expressed as a percentage of its principal amount) equal to the Comparable Treasury Price for such redemption date. The redemption price and the Treasury Rate will be determined by us.

“Comparable Treasury Issue” means the United States Treasury security selected by the Reference Treasury Dealer as having a maturity comparable to the remaining term of the Notes to be redeemed that would be utilized, at the time of selection and in accordance with customary financing practice, in pricing new issues of corporate debt securities of comparable maturity to the remaining term of the Notes being redeemed.

“Comparable Treasury Price” means (1) the average of the remaining Reference Treasury Dealer Quotations for the redemption date, after excluding the highest and lowest Reference Treasury Dealer Quotations, or (2) if the Quotation Agent obtains fewer than four such Reference Treasury Dealer quotations, the average of all such quotations.

“Quotation Agent” means a Reference Treasury Dealer selected by us.

“Reference Treasury Dealer” means (1) BofA Securities, Inc. or its respective affiliates which are primary U.S. government securities dealers in the United States (a “Primary Treasury Dealer”) and their respective successors; provided, however, that if the foregoing or its affiliates shall cease to be a Primary Treasury Dealer, we shall select another Primary Treasury Dealer, and (2) three other Primary Treasury Dealers selected by us.

“Reference Treasury Dealer Quotations” means, with respect to each Reference Treasury Dealer and any redemption date, the average, as determined by the Quotation Agent, of the bid and asked prices for the Comparable Treasury Issue (expressed in each case as a percentage of its principal amount) quoted in writing to the Quotation Agent by such Reference Treasury Dealer at 3:30 p.m. New York time on the third business day preceding such redemption date.

All determinations made by any Reference Treasury Dealer, including the Quotation Agent, with respect to determining the redemption price will be final and binding absent manifest error.

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

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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 facility. In addition, the indentures governing the Convertible Notes and the 2023 Notes each contains a provision that would require us to offer to purchase the respective Convertible Notes or 2023 Notes upon the occurrence of a fundamental change. A failure to purchase any tendered Convertible Notes or 2023 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 2019 Q2 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.”

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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:

“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

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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) TSL Advisers LLC or any affiliate of TSL 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 will provide 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 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:

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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

Events of Default

Each of the following is an event of default:

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If an event of default occurs and is continuing, 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 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:

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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 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

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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

Wells Fargo Bank, National Association is the trustee, security registrar and paying agent. Wells Fargo Bank, National Association, in each of its capacities, including without limitation as trustee, security registrar and paying agent, assumes no responsibility for the accuracy 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.

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:

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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 nor the underwriters are responsible for those operations or procedures.

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.

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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.

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.

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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) or any state, local or foreign tax consequences.

The discussion below is based upon the provisions of the Code, and 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 or otherwise subject to U.S. federal income tax on a net income basis in respect of the Notes. 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 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.

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Consequences to U.S. Holders of Notes

Book/Tax Conformity

U.S. Holders that use an accrual method of accounting for tax purposes (“accrual method holders”) generally are required to include certain amounts in income no later than the time such amounts are reflected on certain financial statements (the “book/tax conformity rule”). The application of the book/tax conformity rule thus may require the accrual of income earlier than would be the case under the general tax rules described below. It is not entirely clear to what types of income the book/tax conformity rule applies, or, in some cases, how the rule is to be applied if it is applicable. However, recently released proposed regulations generally would exclude, among other items, original issue discount and market discount (in either case, whether or not de minimis) from the applicability of the book/tax conformity rule. Although the proposed regulations generally will not be effective until taxable years beginning after the date on which they are issued in final form, taxpayers generally are permitted to elect to rely on their provisions currently. Accrual method holders should consult with their tax advisors regarding the potential applicability of the book/tax conformity rule to their particular situation.

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. It is anticipated, and this discussion assumes, that the Notes will be issued with no more than a de minimis amount of original issue discount (as defined in applicable Treasury regulations). If, however, the Notes are issued for an amount less than the principal amount and the difference is more than a de minimis amount, 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. 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 received 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:

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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.

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. Holders. In addition, certain U.S. Holders 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. Non-U.S. Holders generally are exempt from information reporting and backup withholding, provided, if necessary, that they demonstrate their qualification for exemption. Any amounts withheld under the backup withholding rules from a payment to a U.S. or Non-U.S. Holder 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. An intergovernmental agreement between the United States and an applicable foreign country, or future Treasury Regulations or other guidance, may modify these requirements. 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 or proceeds 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. 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.

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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

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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 $        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 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.

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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, 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.

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.

Principal Business Addresses

The principal business address of BofA Securities, Inc. is One Bryant Park, New York, NY 10036.

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.

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

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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”); or (ii) a customer within the meaning of Directive 2002/92/EC (as amended, the “Insurance Mediation 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 the Notes. This prospectus supplement and the accompanying prospectus is not a prospectus for the purposes of the Prospectus Regulation.

Notice to Prospective Investors in the United Kingdom

This document is only being distributed to and is only directed at (i) persons who are outside the United Kingdom or (ii) investment professionals falling within Article 19 (5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (the “Order”) or (iii) high net worth entities and other persons to whom it may lawfully be communicated falling within Article 49(2)(a) to (d) of the Order (all such persons together being referred to as “relevant persons”). Any Notes will only be available to, and any invitation, offer or agreement to subscribe, purchase or otherwise acquire such Notes will be engaged in only with, relevant persons. Any person who is not a relevant person should not act or rely on this document or any of its contents.

Each underwriter has represented and agreed that:

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 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

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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.

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.

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Notice to Prospective Investors in Switzerland

This prospectus supplement does not constitute an issue prospectus pursuant to Article 652a or Article 1156 of the Swiss Code of Obligations and the Notes will not be listed on the SIX Swiss Exchange. Therefore, this prospectus supplement may not comply with the disclosure standards of the listing rules (including any additional listing rules or prospectus schemes) of the SIX Swiss Exchange. Accordingly, the Notes may not be offered to the public in or from Switzerland, but only to a selected and limited circle of investors who do not subscribe to the Notes with a view to distribution. Any such investors will be individually approached by the underwriters from time to time.

Notice to Prospective Investors in The Netherlands

Each underwriter, severally and not jointly, has agreed that it has not offered or sold, and will not offer or sell, the Notes to the public in The Netherlands, other than exclusively to qualified investors (gekwalificeerde beleggers) within the meaning of the Financial Supervision Act (Wet op het financieel toezicht). For the purposes of this provision, the expression “offer of notes to the public” in relation to any Notes in The Netherlands means to make a sufficiently specific offer addressed to more than one person as referred to in section 217(1) of Book 6 of the Dutch Civil Code to conclude a contract to purchase or otherwise acquire the Notes, or to issue an invitation to make an offer of the Notes.

Notice to Prospective Investors in France

Neither this prospectus supplement nor the accompanying prospectus has been submitted to the clearance procedures of the Autorité des Marchés Financiers or of the competent authority of another member state of the European Economic Area and notified to the Autorité des Marchés Financiers. The Notes have not been offered or sold, and will not be offered or sold, directly or indirectly, to the public in France. Neither this prospectus supplement nor the accompanying prospectus has been or will be:

The Notes may be resold directly or indirectly, only in compliance with articles L.411-1, L.411-2, L.412-1 and L.621-8 through L.621-8-3 of the French Code monétaire et financier.

Notice to Prospective Investors in Germany

This prospectus supplement and the accompanying prospectus have not been prepared in accordance with the requirements for a securities or sales prospectus under the German Securities Prospectus Act (Wertpapierprospektgesetz), the German Sales Prospectus Act (Verkaufsprospektgesetz), or the German Investment Act (Investmentgesetz). Neither the German Federal Financial Services Supervisory Authority (Bundesanstalt für Finanzdienstleistungsaufsicht — BaFin) nor any other German authority has been notified of

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the intention to distribute the Notes in Germany. Consequently, the Notes may not be distributed in Germany by way of public offering, public advertisement or in any similar manner and this prospectus supplement and the accompanying prospectus and any other document relating to this offering, as well as information or statements contained therein, may not be supplied to the public in Germany or used in connection with any offer for subscription of the Notes to the public in Germany or any other means of public marketing. The Notes are being offered and sold in Germany only to qualified investors which are referred to in Section 3, paragraph 2 no. 1, in connection with Section 2, no. 6, of the German Securities Prospectus Act, Section 8f paragraph 2 no. 4 of the German Sales Prospectus Act, and in Section 2 paragraph 11 sentence 2 no. 1 of the German Investment Act. This prospectus supplement and the accompanying prospectus is strictly for use of the person who has received it. It may not be forwarded to other persons or published in Germany.

This offering of our Notes does not constitute an offer to buy or the solicitation or an offer to sell the Notes in any circumstances in which such offer or solicitation is unlawful.

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LEGAL MATTERS

Certain legal matters in connection with the offering will be passed upon for us by Cleary Gottlieb Steen & Hamilton LLP, New York, New York. In addition, Schulte Roth & Zabel LLP and Morris, Nichols, Arsht & Tunnell LLP will pass on certain legal matters for us. Cleary Gottlieb Steen & Hamilton LLP and Schulte Roth & Zabel LLP also represent the Adviser. Certain legal matters in connection with the offering will be passed upon for the underwriters by Ropes & Gray LLP, New York, New York.

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PROSPECTUS

$750,000,000

TPG Specialty Lending, Inc.

Common Stock

Preferred Stock

Subscription Rights

Warrants

Debt Securities

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 March 31, 2019, our investment portfolio consisted of investments in 48 portfolio companies with an aggregate fair value of $1,824.9 million. We intend to continue to pursue an investment strategy focused on direct origination of loans to middle-market companies principally domiciled in the United States.

We are an externally managed, closed-end, non-diversified management investment company. TSL Advisers, LLC, or the Adviser, acts as our investment adviser and administrator. We and the Adviser are part of the TPG Sixth Street Partners platform, which had over $30 billion of assets under management as of December 31, 2018. TPG Sixth Street Partners is the global finance and investment firm in a strategic relationship with TPG, the global alternative asset firm.

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 Canadian Dollar Offered Rate, the Bank Bill Swap Bid Rate, the Euro Interbank Offered 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 up to $750 million 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, 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 May 6, 2019, the last reported sales price of our common stock on the NYSE was $20.21 per share. The net asset value per share of our common stock at March 31, 2019 (the last date prior to the date of this prospectus for which we reported net asset value) was $16.34.

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 23 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, 35th Floor, New York, NY 10106, Attention: TSLX Investor Relations, by emailing us at IRTSL@tpg.com or visiting our website at http://www.tpgspecialtylending.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 May 7, 2019

CROSS-REFERENCE SHEET

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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.

TABLE OF CONTENTS

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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, or 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, up to $750 million 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.

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.

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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 2018 Annual Report and Part 1, Item IA, “Risk Factors,” in our 2019 Q1 Quarterly Report, which are incorporated herein by reference, together with the other information set forth in this prospectus 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 2018 Annual Report and our 2019 Q1 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

There is a risk that investors in our common stock may not receive dividends or that our dividends may not grow over time.

We intend to continue paying dividends on a quarterly basis to our stockholders out of assets legally available for distribution. We cannot assure you that we will achieve investment results or maintain a tax status that will allow or require any specified level of cash dividends or year-to-year increases in cash dividends. Our ability to pay dividends might be adversely affected by the impact of one or more of the risk factors described in this prospectus. Due to the asset coverage test applicable to us under the 1940 Act as a BDC or restrictions under our credit facilities, we may be limited in our ability to pay dividends. Although a portion of our expected earnings and dividend distributions will be attributable to net interest income, we do not expect to generate capital gains from the sale of our portfolio investments on a level or uniform basis from quarter to quarter. This may result in substantial fluctuations in our quarterly dividend payments.

In some cases where we receive certain upfront fees in connection with loans we originate, we treat the loan as having OID under applicable accounting and tax regulations, even though we have received the corresponding cash. In other cases, however, we may recognize income before or without receiving the corresponding cash, including in connection with the accretion of OID. For other risks associated with debt obligations treated as having OID, see “Risk Factors—Risks Related to Our Portfolio Company Investments—There are certain risks associated with holding debt obligations that have original issue discount or payment-in-kind interest” in Part I, Item 1A of our 2018 Annual Report.

Therefore, we may be required to make a distribution to our stockholders in order to satisfy the annual distribution requirement necessary to qualify for and maintain RIC tax treatment under Subchapter M of the Code, even though we may not have received the corresponding cash amount. Accordingly, we may have to sell investments at times we would not otherwise consider advantageous, raise additional debt or equity capital or reduce new investment originations to meet these distribution requirements for this purpose. If we are not able to obtain cash from other sources, we may fail to qualify as a RIC and thereby be subject to corporate-level income tax.

To the extent that the amounts distributed by us exceed our current and accumulated earnings and profits, these 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 part of the Incentive Fee payable by us that relates to our net investment income is computed and paid on income that may include interest that has been accrued but not yet received in cash. If a portfolio company defaults on a loan, it is possible that accrued interest previously used in the calculation of the Incentive Fee will become uncollectible. Consequently, while we may make Incentive Fee payments on income accruals that we

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may not collect in the future and with respect to which we do not have a clawback right against our Adviser, the amount of accrued income written off in any period will reduce the income in the period in which the write-off is taken and thereby reduce that period’s Incentive Fee payment, if any.

In addition, the middle-market companies in which we intend to invest may be more susceptible to economic downturns than larger operating companies, and therefore may be more likely to default on their payment obligations to us during recessionary periods. Any such defaults could substantially reduce our net investment income available for distribution in the form of dividends to our stockholders.

Investing in our securities may involve a high degree of risk.

The investments we make in accordance with our investment objective may result in a higher amount of risk than alternative investment options and volatility or loss of principal. Our investments in portfolio companies may be highly speculative and aggressive and, therefore, an investment in our securities may not be suitable for someone with lower risk tolerance.

The market price of our common stock may fluctuate significantly.

The market price and liquidity of the market for shares of our common stock may be significantly affected by numerous factors, some of which are beyond our control and may not be directly related to our operating performance. These factors include:

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In the past, following periods of volatility in the market price of a company’s securities, securities class action litigation has often been brought against that company. If our stock price fluctuates significantly, we may be the target of securities litigation in the future. Securities litigation could result in substantial costs and divert management’s attention and resources from our business.

We cannot assure you that the market price of shares of our common stock will not decline.

Shares of closed-end investment companies, including BDCs, frequently trade at a discount from their net asset value and our stock may also be discounted in the market. This characteristic of closed-end investment companies is separate and distinct from the risk that our net asset value per share of common stock may decline. In the past, shares of BDCs, including at times shares of our common stock, have traded at prices per share below net asset value per share. We cannot predict whether our common stock will trade at a price per share above, at or below net asset value per share. In addition, if our common stock trades below its net asset value per share, we will generally not be able to sell additional shares of our common stock to the public at its market price without first obtaining the approval of a majority of our stockholders (including a majority of our unaffiliated stockholders) and our Independent Directors for such issuance.

Sales of substantial amounts of our common stock in the public market may have an adverse effect on the market price of our common stock.

Sales of substantial amounts of our common stock, the availability of such common stock for sale (including as a result of the conversion of our 2019 Convertible Notes and our 2022 Convertible Notes into common stock) or the perception that such sales could occur could adversely affect the prevailing market prices for our common stock. If this occurs, it could impair our ability to raise additional capital through the sale of equity securities should we desire to do so. We cannot predict what effect, if any, future sales of securities or the availability of securities for future sales will have on the market price of our common stock prevailing from time to time.

Our stockholders may experience dilution upon the conversion of the 2019 Convertible Notes and the 2022 Convertible Notes.

Our 2019 Convertible Notes and our 2022 Convertible Notes are convertible into shares of our common stock beginning on June 15, 2019 and February 1, 2022, respectively, or earlier, under certain circumstances. Upon conversion of our 2019 Convertible Notes and 2022 Convertible Notes, we have the choice to pay or deliver, as the case may be, at our election, cash, shares of our common stock or a combination of cash and shares of our common stock. The initial conversion price of the 2019 Convertible Notes was $25.83 per share and the initial conversion price of the 2022 Convertible Notes was $21.34 per share. As the result of our payment of certain cash dividends in respect of our common stock, as of March 31, 2019, the estimated adjusted conversion price of the 2019 Convertible Notes is $24.91 per share, and the estimated adjusted conversion price of the 2022 Convertible Notes is $20.79 per share, in each case taking into account certain de minimis adjustments that will be made on the conversion date and subject to further adjustment in certain circumstances. If we elect to deliver shares of common stock upon a conversion at the time our tangible book value per share exceeds the conversion price in effect at such time, our stockholders may incur dilution. In addition, our stockholders will experience dilution in their ownership percentage of common stock upon our issuance of

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common stock in connection with the conversion of the 2019 Convertible Notes and the 2022 Convertible Notes and any dividends paid on our common stock will also be paid on shares issued in connection with such conversion after such issuance.

Our stockholders will experience dilution in their ownership percentage if they opt out of our dividend reinvestment plan.

We have adopted a dividend reinvestment plan, pursuant to which we will reinvest all cash dividends and distributions declared by the Board on behalf of investors who do not elect to receive their dividends in cash. As a result, if the Board authorizes, and we declare, a cash dividend or other distribution, then our stockholders who have not opted out of our dividend reinvestment plan will have their cash distributions automatically reinvested in additional common stock, rather than receiving the cash dividend or other distribution. See “Price Range of Common Stock and Distributions” and “Dividend Reinvestment Plan” for a description of our dividend policy and obligations.

In addition, the number of shares issued pursuant to the dividend reinvestment plan will be determined based on the market price of shares of our common stock, except in circumstances where the market price exceeds our most recently computed net asset value per share, in which case we will issue shares at the greater of (i) the most recently computed net asset value per share and (ii) 95% of the current market price per share or such lesser discount to the current market price per share that still exceeds the most recently computed net asset value per share. Accordingly, participants in the dividend reinvestment plan may receive a greater number of shares of our common stock than the number of shares associated with the market price of our common stock, resulting in dilution for other stockholders. Stockholders that opt out of our dividend reinvestment plan will experience dilution in their ownership percentage of our common stock over time.

Purchases of our common stock by us under the Company 10b5-1 Plan may result in the price of our common stock being higher than the price that otherwise might exist in the open market.

We have entered into an agreement with Goldman Sachs & Co. LLC, which we refer to as the Company 10b5-1 Plan, in accordance with Rules 10b5-1 and 10b-18 under the Exchange Act, under which Goldman Sachs & Co. LLC, as agent for us, will buy up to $50 million of our common stock in the aggregate during the period ending on the earlier of the date on which all the capital committed to the plan has been exhausted or November 30, 2019.

Whether purchases will be made under the Company 10b5-1 Plan and how much will be purchased at any time is uncertain, dependent on prevailing market prices and trading volumes, all of which we cannot predict. These activities may have the effect of maintaining the market price of our common stock or retarding a decline in the market price of the common stock, and, as a result, the price of our common stock may be higher than the price that otherwise might exist in the open market.

Purchases of our common stock by us under the Company 10b5-1 Plan may result in dilution to our net asset value per share.

On May 2, 2019, the Board authorized an amendment to the Company 10b5-1 Plan to, among other things, revise the market prices at which Goldman Sachs & Co. LLC, as our agent, is required to repurchase shares of common stock on our behalf from just below our most recently reported net asset value per share to just below 1.05 times the most recently reported net asset value per share, less the amount of any supplemental dividend declared for that quarter but not yet reflected in the most recently reported net asset value per share (including any updates, corrections or adjustments publicly announced by us to any previously announced net asset value per share or supplemental dividend). Under the Company 10b5-1 Plan, the agent will increase the volume of purchases made as the price of our common stock declines, subject to volume restrictions.

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Dilution to our net asset value per share will occur if we purchase shares of our common stock at a price above the net asset value per share, as it would cause a proportionately smaller increase in our stockholders’ interest in our earnings and assets and their voting interest in us than the decrease in our assets resulting from such repurchase.

As a result of any such dilution, our market price per share may decline. The actual dilutive effect will depend on the number of shares of common stock that could be so repurchased, the price and the timing of any repurchases under the Company 10b5-1 Plan.

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 17, 2018, 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 17, 2019. On April 5, 2019, we filed a definitive proxy statement for a special meeting of stockholders, to be held on May 16, 2019. The definitive proxy statement sets forth a proposal to be voted upon at the special meeting that, if approved by stockholders, would have the effect of extending this approval to the one-year anniversary of the date of the special meeting.

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.

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.

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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 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.

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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 of our 2018 Annual Report and Part II, Item 1A of our 2019 Q1 Quarterly 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.

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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.

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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, 2019 and for the years ended December 31, 2018 and 2017. On May 6, 2019, the last reported closing sales price of our common stock on the NYSE was $20.21 per share, which represented a premium of approximately 23.7% to the net asset value per share reported by us as of March 31, 2019, 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.

On May 2, 2019, our Board declared a second quarter 2019 base dividend of $0.39 per share for stockholders of record as of June 14, 2019, payable on July 15, 2019. Our Board also declared a first quarter variable supplemental dividend of $0.01 per share for stockholders of record as of May 31, 2019, payable on June 28, 2019. We anticipate that these dividends will be paid from income generated primarily by interest earned on our investment portfolio.

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The following tables summarize dividends declared during the three months ended March 31, 2019 and years ended December 31, 2018 and 2017: