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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Thousands |  |  | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | --- | ---
Apr. 05, 2024 | Apr. 04, 2024 | Jun. 30, 2024 USD ($) loan investment | Jun. 30, 2023 USD ($) | Jun. 30, 2024 USD ($) loan investment | Jun. 30, 2023 USD ($) | Sep. 30, 2023 USD ($) investment loan
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |
Reverse stock split, conversion ratio | 0.5 | 0.5 |  |  |  |  |  |
Cost |  |  | $ 753,263 |  | $ 753,263 |  | $ 722,269 | [1]
Investments, at fair value |  |  | 757,745 |  | 757,745 |  | 704,815 | [1]
Total interest income (excluding PIK interest income) |  |  | 21,715 | $ 20,971 | 65,633 | $ 57,143 |  |
PIK interest income |  |  | 1,484 | 845 | 4,277 | 2,618 |  |
OID |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |
Investments, at fair value |  |  | $ 800 |  | $ 800 |  | $ 700 |
Number of loans | loan |  |  | 3 |  | 3 |  | 4 |
Total interest income (excluding PIK interest income) |  |  | $ 100 | 49 | $ 200 | 200 |  |
PIK |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |
Number of investments | investment |  |  | 11 |  | 11 |  | 8 |
Proceeds from interest received |  |  | $ 200 | $ 0 | $ 200 | $ 400 |  |
B+T Group Acquisition, Inc., Edge Adhesives Holdings, Inc,. and WB Xcel Holdings, LLC |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |
Cost |  |  | $ 26,400 |  | $ 26,400 |  |  |
Cost percentage |  |  | 3.90% |  | 3.90% |  |  |
Investments, at fair value |  |  | $ 13,900 |  | $ 13,900 |  |  |
Fair value percentage |  |  | 2.10% |  | 2.10% |  |  |
Edge Adhesives Holdings, Inc. |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |
Cost |  |  |  |  |  |  | $ 6,100 |
Cost percentage |  |  |  |  |  |  | 0.90% |
Investments, at fair value |  |  |  |  |  |  | $ 2,900 |
Fair value percentage |  |  |  |  |  |  | 0.50% |
[1] | Cumulative gross unrealized depreciation for federal income tax purposes is $56.9 million; cumulative gross unrealized appreciation for federal income tax purposes is $33.7 million. Cumulative net unrealized depreciation is $23.2 million, based on a tax cost of $728.0 million.

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