西南资本美股招股说明书(2026-08-07版)

Supplement No.7, dated August 7, 2026toProspectus, dated October 29, 2024 andProspectus Supplement, dated October 30, 2024 This supplement amends, supplements or modifies certain information contained in the prospectus supplement, dated October 30, 2024 (the“ATM Prospectus Supplement”), and the accompanying prospectus, dated October 29, 2024 (the “Base Prospectus,” and together with theATM Prospectus Supplement and the documents deemed incorporated by reference in each, the “Prospectus”), which relate to the sale ofshares of common stock of Capital Southwest Corporation in an “at-the-market” offering (the “ATM Program”) pursuant to certain equitydistribution agreements (as described below). The terms the “Company,” “CSWC,” “we,” “us,” and “our” refer to Capital SouthwestCorporation and its subsidiaries, unless indicated otherwise. Capitalized terms used but not defined herein shall have the same meaninggiven them in the ATM Prospectus Supplement. You should carefully read the entire Prospectus and this supplement before investing in our common stock. This supplement should be readin conjunction with the Prospectus.You should also carefully consider the information set forth under the sections entitled “Risk Factors”on page S-9 of the ATM Prospectus Supplement, page 10 of the Base Prospectus and in our Annual Report on Form 10-K for the fiscalyear ended March 31, 2026, which is incorporated by reference into the Prospectus, as well as in our subsequent filings with theSecurities and Exchange Commission that are incorporated into the Prospectus, before investing in our common stock. On March 4, 2019, we initially established the ATM Program to which the Prospectus relates, and through which we may sell, from time totime through sales agents, up to a maximum aggregate amount of $2,000,000,000 in shares of our common stock. In connection with theATM Program, we have entered into those certain (i) third amended and restated equity distribution agreements, each dated May 26, 2021and as amended from time to time, with each of Jefferies LLC (“Jefferies”) and Raymond James & Associates, Inc. (“Raymond James”) and(ii) amended and restated equity distribution agreements, each dated May 26, 2021 and as amended from time to time, with each of CitizensJMP Securities, LLC (“Citizens Capital Markets”) and B. Riley Securities, Inc. (“B. Riley”). This supplement is being filed to reflect that, on August 7, 2026, we added an additional sales agent to the ATM Program, RBC CapitalMarkets, LLC ("RBC" and, together with Jefferies, Raymond James, Citizens Capital Markets and B. Riley, the “Sales Agents”). Inconnection therewith, we entered into that certain equity distribution agreement, dated August 7, 2026, with RBC. The Company’s equitydistribution agreements with each of the Sales Agents are on substantially the same terms and conditions as one another. In light of the above, each reference to the term “Sales Agent” or “Sales Agents” in the ATM Prospectus Supplement is hereby amended toinclude Jefferies, Raymond James, Citizens Capital Markets, B. Riley, and RBC. We will pay the Sales Agents a commission of 1.5% of the gross sales price of shares of our common stock sold through them pursuant tothe ATM Program. The estimated offering expenses payable by us, in addition to such commission and reimbursement of expenses, areapproximately $4,100,000 (of which we have incurred $2,290,000 as of August 5, 2026), which includes legal, accounting and printing costsand various other fees associated with registering the shares of common stock and the filing fees incident to the review by the FinancialIndustry Regulatory Authority, Inc. (“FINRA”) of the terms of the sale of our common stock in the ATM Program, as well as thereimbursement of certain reasonable fees and expenses of counsel to the Sales Agents incurred in connection with the initial launch of theATM Program (including legal fees and expenses relating to the review by FINRA of the terms of the sale of our common stock in the ATMProgram), and up to $12,500 per calendar quarter during the term of the equity distribution agreements for fees and expenses of counsel tothe Sales Agents incurred in connection with quarterly updates for the ATM Program. The remaining sales proceeds, after deducting any other transaction fees, will equalour net proceeds from the sale of such shares. The principal business address of Jefferies is 520 Madison Avenue, New York, New York 10022. The principal business address of RaymondJames is 880 Carillon Parkway, St. Petersburg, Florida 33716. The principal business address of Citizens Capital Markets is 101 CaliforniaStreet, Suite 1700, San Francisco, California 94111. The principal business address of B. Riley is 299 Park Avenue, 21st Floor, New York,New York 10171. The principal business address of RBC is 200 Vesey Street, 8th Floor, New York, New York 10281. STATUS OF THE "AT-THE-MARKET" OFFERING From March 4, 2019 to June 30, 2026, we sol