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FAIR VALUE MEASUREMENTS - Valuation Techniques and Significant Level 3 Inputs (Details) $ in Thousands | Sep. 30, 2025 USD ($) | Mar. 31, 2025 USD ($)
--- | --- | ---
Fair Value |  |  |  |
Investments at fair value | $ 1,877,907 | [1],[2],[3],[4],[5] | $ 1,785,299 | [6],[7],[8],[9],[10]
Significant Unobservable Inputs (Level 3) |  |  |  |
Fair Value |  |  |  |
Investments at fair value | 1,877,907 |  | 1,785,299 |
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Discount Rate |  |  |  |
Fair Value |  |  |  |
Investments at fair value | 1,575,199 |  | 1,448,656 |
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Third Party Broker Quote |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 3,413 |  | $ 6,923 |
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Minimum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.050 |  | 0.052 |
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Minimum | Third Party Broker Quote |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.404 |  | 0.400 |
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Maximum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.882 |  | 0.647 |
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Maximum | Third Party Broker Quote |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.700 |  | 1.000 |
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Weighted Average | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.121 |  | 0.128 |
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Weighted Average | Third Party Broker Quote |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.608 |  | 0.798 |
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 93,094 |  | $ 125,500 |
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach | Minimum | Cost |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.971 |  | 0.898 |
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach | Maximum | Cost |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 1.000 |  | 1.000 |
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach | Weighted Average | Cost |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.974 |  | 0.979 |
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 16,236 |  | $ 5,543 |
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach | Minimum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.126 |  | 0.210 |
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 9.0 |  | 3.0 |
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach | Maximum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.193 |  | 0.492 |
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 9.5 |  | 9.0 |
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.148 |  | 0.210 |
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 9.3 |  | 3.0 |
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 17,170 |  |  |
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Discount Rate |  |  |  |
Fair Value |  |  |  |
Investments at fair value |  |  | $ 18,066 |
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Minimum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.098 |  | 0.095 |
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Maximum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 1.172 |  | 0.412 |
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Weighted Average | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.172 |  | 0.133 |
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 0 |  | $ 0 |
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Minimum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.228 |  | 0.210 |
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 3.0 |  | 3.0 |
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Maximum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.228 |  | 0.210 |
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 3.0 |  | 3.0 |
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.000 |  | 0.000 |
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.0 |  | 0.0 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Income Approach | Discount Rate |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 524 |  | $ 538 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Income Approach | Third Party Broker Quote |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 58 |  | $ 58 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Income Approach | Minimum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.123 |  | 0.144 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Income Approach | Minimum | Third Party Broker Quote |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.254 |  | 0.250 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Income Approach | Maximum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.123 |  | 0.144 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Income Approach | Maximum | Third Party Broker Quote |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.254 |  | 0.250 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Income Approach | Weighted Average | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.123 |  | 0.144 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Income Approach | Weighted Average | Third Party Broker Quote |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.254 |  | 0.250 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Market Approach |  |  |  |
Fair Value |  |  |  |
Investments at fair value |  |  | $ 65 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Market Approach | Minimum | Cost |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs |  |  | 1.000 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Market Approach | Maximum | Cost |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs |  |  | 1.000 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Market Approach | Weighted Average | Cost |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs |  |  | 1.000 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 557 |  | $ 557 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Minimum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.145 |  | 0.133 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 6.2 |  | 6.1 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Maximum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.175 |  | 0.176 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 7.9 |  | 7.6 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.154 |  | 0.147 |
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 6.7 |  | 6.6 |
Significant Unobservable Inputs (Level 3) | Preferred equity | Market Approach |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 2,000 |  | $ 2,900 |
Significant Unobservable Inputs (Level 3) | Preferred equity | Market Approach | Minimum | Cost |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 1.000 |  | 1.000 |
Significant Unobservable Inputs (Level 3) | Preferred equity | Market Approach | Maximum | Cost |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 1.000 |  | 1.000 |
Significant Unobservable Inputs (Level 3) | Preferred equity | Market Approach | Weighted Average | Cost |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 1.000 |  | 1.000 |
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 64,474 |  | $ 100,018 |
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Minimum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.118 |  | 0.111 |
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 3.0 |  | 3.0 |
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Maximum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.480 |  | 0.492 |
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 16.7 |  | 16.9 |
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.166 |  | 0.159 |
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 7.9 |  | 8.8 |
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 1,335 |  | $ 1,597 |
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Minimum | Cost |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 1.000 |  | 1.000 |
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Maximum | Cost |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 1.000 |  | 1.000 |
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Weighted Average | Cost |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 1.000 |  | 1.000 |
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 100,105 |  | $ 74,878 |
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Minimum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.111 |  | 0.119 |
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 3.0 |  | 3.0 |
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Maximum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.249 |  | 0.233 |
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 16.7 |  | 16.0 |
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.149 |  | 0.144 |
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 8.8 |  | 8.4 |
Significant Unobservable Inputs (Level 3) | Earnout | Income Approach |  |  |  |
Fair Value |  |  |  |
Investments at fair value | $ 3,742 |  |  |
Significant Unobservable Inputs (Level 3) | Earnout | Income Approach | Minimum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.337 |  |  |
Significant Unobservable Inputs (Level 3) | Earnout | Income Approach | Maximum | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.337 |  |  |
Significant Unobservable Inputs (Level 3) | Earnout | Income Approach | Weighted Average | Discount Rate |  |  |  |
Significant Unobservable Inputs |  |  |  |
Significant Level 3 Inputs | 0.337 |  |  |
[1] | All debt investments are income-producing, unless otherwise noted. Equity investments are non-income producing, unless otherwise noted. (2)All of the Company’s investments, the investments of Capital Southwest SPV LLC ("SPV"), the investments of SBIC I (as defined below) and the investments of SBIC II (as defined below) are pledged as collateral for the Company’s senior secured revolving credit facility, the SPV's financing credit facility or in support of the SBA-guaranteed debentures to be issued by Capital Southwest SBIC I, LP ("SBIC I") and Capital Southwest SBIC II, LP ("SBIC II"), the Company's wholly-owned subsidiaries that operate as small business investment companies, respectively.
[2] | Non-Control/Non-Affiliate investments are generally defined by the 1940 Act as investments that are neither control investments nor affiliate investments. Investments are classified as non-control/non-affiliate investments, unless otherwise noted. At September 30, 2025, the Company held $1,488.4 million of non-control/non-affiliate investments, which represented approximately 79.3% of the Company’s investment assets. The fair value of these investments as a percent of net assets is 157.1%.
[3] | The Company's investment portfolio is comprised entirely of debt and equity securities of privately held companies for which quoted prices falling within the categories of Level 1 and Level 2 inputs are not readily available. Therefore, the Company values all of its portfolio investments at fair value, as determined in good faith by the valuation committee comprised of certain officers of the Company (the "Valuation Committee") as the valuation designee of the Board of Directors (the "Valuation Designee") pursuant to Rule 2a-5 under the Investment Company Act of 1940, as amended (the “1940 Act”), using significant unobservable Level 3 inputs. Refer to Note 4 - Fair Value Measurements for further discussion.
[4] | Equity ownership may be held in shares or units of a company that is either wholly owned by the portfolio company or under common control by the same parent company to the portfolio company.
[5] | Unless otherwise noted, all portfolio company headquarters are based in the United States.
[6] | Equity ownership may be held in shares or units of a company that is either wholly owned by the portfolio company or under common control by the same parent company to the portfolio company.
[7] | Unless otherwise noted, all portfolio company headquarters are based in the United States.
[8] | All debt investments are income-producing, unless otherwise noted. Equity investments are non-income producing, unless otherwise noted.
[9] | Non-Control/Non-Affiliate investments are generally defined by the 1940 Act as investments that are neither control investments nor affiliate investments. Investments are classified as non-control/non-affiliate investments, unless otherwise noted. At March 31, 2025, the Company held $1,436.3 million of non-control/non-affiliate investments, which represented approximately 80.5% of the Company’s investment assets. The fair value of these investments as a percent of net assets is 162.6%.
[10] | The Company's investment portfolio is comprised entirely of debt and equity securities of privately held companies for which quoted prices falling within the categories of Level 1 and Level 2 inputs are not readily available. Therefore, the Company values all of its portfolio investments at fair value, as determined in good faith by the valuation committee comprised of certain officers of the Company (the "Valuation Committee") as the valuation designee of the Board of Directors (the "Valuation Designee") pursuant to Rule 2a-5 under the Investment Company Act of 1940, as amended (the “1940 Act”), using significant unobservable Level 3 inputs. Refer to Note 4 - Fair Value Measurements for further discussion.

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