Significant Accounting Policies and Recent Accounting Updates (Policies)	9 Months Ended
Jun. 30, 2024
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation: The Company is an investment company as defined in the accounting and reporting guidance under Accounting Standards Codification (“ASC”) Topic 946 — Financial Services — Investment Companies (“ASC Topic 946”). The accompanying unaudited interim consolidated financial statements of the Company and related financial information have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) as established by the Financial Accounting Standards Board (“FASB”) for interim financial information and pursuant to the requirements for reporting on Form 10-Q and Articles 6, 10 and 12 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for annual financial statements. In the opinion of management, the consolidated financial statements reflect all adjustments and reclassifications consisting solely of normal accruals that are necessary for the fair presentation of financial results as of and for the periods presented. All intercompany balances and transactions have been eliminated. Certain prior period amounts have been reclassified to conform to the current period presentation. The unaudited interim consolidated financial statements and notes thereto should be read in conjunction with the financial statements and notes thereto in the Company’s Form 10-K for the year ended September 30, 2023, as filed with the U.S. Securities and Exchange Commission (the “SEC”).
Fair value of financial instruments	Fair value of financial instruments: The Company applies fair value to all of its financial instruments in accordance with ASC Topic 820 — Fair Value Measurement (“ASC Topic 820”). ASC Topic 820 defines fair value, establishes a framework used to measure fair value and requires disclosures for fair value measurements. In accordance with ASC Topic 820, the Company has categorized its financial instruments carried at fair value, based on the priority of the valuation technique, into a three-level fair value hierarchy. Fair value is a market-based measure considered from the perspective of the market participant who holds the financial instrument rather than an entity-specific measure. Therefore, when market assumptions are not readily available, the Company’s own assumptions are set to reflect those that management believes market participants would use in pricing the financial instrument at the measurement date. The availability of observable inputs can vary depending on the financial instrument and is affected by a wide variety of factors, including, for example, the type of product, whether the product is new, whether the product is traded on an active exchange or in the secondary market and the current market conditions. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for financial instruments classified as Level 3. Any changes to the valuation methodology are reviewed by management and the Company’s board of directors (the “Board”) to confirm that the changes are appropriate. As markets change, new products develop and the pricing for products becomes more or less transparent, the Company will continue to refine its valuation methodologies.
Use of estimates	Use of estimates: The preparation of the unaudited interim consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Consolidation	Consolidation: As provided under Regulation S-X and ASC Topic 946, the Company will generally not consolidate its investment in a company other than an investment company subsidiary or a controlled operating company whose business consists of providing services to the Company. Assets related to transactions that do not meet ASC Topic 860 requirements for accounting sale treatment are reflected in the Company’s Consolidated Statements of Financial Condition as investments. Those assets are owned by special purpose entities, including BDC Holdings, 2018 Issuer, Funding II, GCIC Holdings, GCIC 2018 Issuer, GBDC 3 Holdings, GBDC 3 Funding, GBDC 3 2021 Issuer, GBDC 3 2022 Issuer and the GBDC 3 2022-2 Issuer, that are consolidated in the Company’s consolidated financial statements. The creditors of the special purpose entities have received security interests in such assets and such assets are not intended to be available to the creditors of GBDC (or any affiliate of GBDC).
Cash and cash equivalents and foreign currencies	Cash and cash equivalents and foreign currencies: Cash and cash equivalents and foreign currencies are highly liquid investments with an original maturity of three months or less at the date of acquisition. The Company deposits its cash in financial institutions and, at times, such balances exceed the Federal Deposit Insurance Corporation insurance limits.
Restricted cash and cash equivalents and restricted foreign currencies	Restricted cash and cash equivalents and restricted foreign currencies: Restricted cash and cash equivalents and restricted foreign currencies include amounts that are collected and are held by trustees who have been appointed as custodians of the assets securing certain of the Company’s financing transactions. Restricted cash and cash equivalents and restricted foreign currencies are held by the trustees for payment of interest expense and principal on the outstanding borrowings or reinvestment into new assets.
Foreign currency translation	Foreign currency translation: The Company’s books and records are maintained in U.S. dollars. Any foreign currency amounts are translated into U.S. dollars. Non-U.S. dollar transactions during the period are valued at the prevailing spot rates on the applicable transaction date and the related assets and liabilities are revalued at the prevailing spot rates as of period-end. Net assets and fair values are presented based on the applicable foreign exchange rates and fluctuations arising from the translation of assets and liabilities are included with the net change in unrealized appreciation (depreciation) on translation of assets and liabilities in foreign currencies on the Consolidated Statements of Operations. Foreign security and currency transactions involve certain considerations and risks not typically associated with investing in U.S. companies. These risks include, but are not limited to, currency fluctuations and revaluations and future adverse political, social and economic developments, which could cause investments in foreign markets to be less liquid and prices more volatile than those of comparable U.S. companies or U.S. government securities.
Derivative Instruments	Derivative Instruments: The Company follows the guidance in ASC Topic 815, Derivatives and Hedging (“ASC Topic 815”), when accounting for derivative instruments. Forward currency contracts: A forward currency contract is an obligation between two parties to purchase or sell a specific currency for an agreed-upon price at a future date. The Company utilized forward currency contracts to economically hedge the currency exposure associated with certain foreign-denominated investments. The use of forward currency contracts does not eliminate fluctuations in the price of the underlying securities the Company owns or intends to acquire but establishes a rate of exchange in advance. Fluctuations in the value of these contracts are measured by the difference in the exchange rates on the contract date and reporting date and are recorded as unrealized appreciation (depreciation) until the contracts are closed. When the contracts are closed, realized gains (losses) are recorded. Realized gains (losses) and unrealized appreciation (depreciation) on the contracts are included in the Consolidated Statements of Operations. Unrealized appreciation (depreciation) on forward currency contracts is recorded on the Consolidated Statements of Financial Condition by counterparty on a net basis, not taking into account collateral posted which is recorded separately, if applicable. The primary risks associated with forward currency contracts include failure of the counterparty to meet the terms of the contract and the value of the foreign currency changing unfavorably. These risks can exceed the amounts reflected in the Consolidated Statements of Financial Condition. Refer to Note 5 for more information regarding the forward currency contracts. Interest rate swaps: The Company designated interest rate swaps as the hedging instrument in qualifying fair value hedge accounting relationships, and as a result, the change in fair value of the hedging instruments and hedged items are recorded in interest expense and recognized as components of “interest expense” in the Company’s Consolidated Statement of Operations. The fair value of the interest rate swaps is included as a component of “Accounts payable and other liabilities” on the Company's Consolidated Statements of Financial Condition. Refer to Note 5 for more information regarding the interest rate swaps.
Revenue recognition	Revenue recognition: Investments and related investment income: Interest income is accrued based upon the outstanding principal amount and contractual interest terms of debt investments. Loan origination fees, original issue discount and market discount or premium are capitalized, and the Company accretes or amortizes such amounts over the life of the loan as interest income.For investments with contractual payment-in-kind (“PIK”) interest, which represents contractual interest accrued and added to the principal balance that generally becomes due at maturity, the Company will not accrue PIK interest if the portfolio company valuation indicates that the PIK interest is not collectible.In addition, the Company generates revenue in the form of amendment, structuring or due diligence fees, fees for providing managerial assistance, consulting fees, administrative agent fees, and prepayment premiums on loans. The Company records these fees as fee income when earned. Dividend income on equity securities is recorded as dividend income on an accrual basis to the extent that such amounts are payable by the portfolio company and are expected to be collected. The Company has certain preferred equity securities in the portfolio that contain a PIK dividend provision that are accrued and recorded as income at the contractual rates, if deemed collectible. The accrued PIK and non-cash dividends are capitalized to the cost basis of the preferred equity security and are generally collected when redeemed by the issuer. Dividend income on common equity securities is recorded on the record date for private portfolio companies or on the ex-dividend date for publicly traded portfolio companies. Each distribution received from limited liability company (“LLC”) and limited partnership (“LP”) investments is evaluated to determine if the distribution should be recorded as dividend income or a return of capital. Generally, the Company will not record distributions from equity investments in LLCs and LPs as dividend income unless there are sufficient accumulated tax-basis earnings and profits in the LLC or LP prior to the distribution. Distributions that are classified as a return of capital are recorded as a reduction in the cost basis of the investment.
Investment transactions	Investment transactions are accounted for on a trade-date basis. Realized gains or losses on investments are measured by the difference between the net proceeds from the disposition and the amortized cost basis of investment, without regard to unrealized gains or losses previously recognized. The Company reports current period changes in fair value of investments that are measured at fair value as a component of the net change in unrealized appreciation (depreciation) on investment transactions in the Consolidated Statements of Operations.
Non-accrual loans	Non-accrual loans: A loan can be left on accrual status during the period the Company is pursuing repayment of the loan. Management reviews all loans that become 90 days or more past due on principal and interest, or when there is reasonable doubt that principal or interest will be collected, for possible placement on non-accrual status. When a loan is placed on non-accrual status, unpaid interest credited to income is reversed. Additionally, any original issue discount and market discount are no longer accreted to interest income as of the date the loan is placed on non-accrual status. Interest payments received on non-accrual loans are recognized as income or applied to principal depending upon management’s judgment. Non-accrual loans are restored to accrual status when past due principal and interest is paid and, in management’s judgment, payments are likely to remain current.
Purchase accounting	Purchase accounting: Pursuant to the GCIC Merger Agreement, the GCIC Merger Sub was first merged with and into GCIC, with GCIC as the surviving company (the “Initial GCIC Merger”), and, immediately following the Initial GCIC Merger, GCIC was then merged with and into the Company, with the Company as the surviving company (the Initial GCIC Merger and the subsequent merger, collectively, the “GCIC Merger”). Pursuant to the GBDC 3 Merger Agreement, the GBDC 3 Merger Sub was first merged with and into GBDC 3, with GBDC 3 as the surviving company in the Initial GBDC 3 Merger and, immediately following the Initial GBDC 3 Merger, GBDC 3 was then merged with and into the Company, with the Company as the surviving company. The GCIC Merger and the GBDC 3 Merger were accounted for under the asset acquisition method of accounting in accordance with ASC 805 — Business Combinations — Related Issues (“ASC Topic 805”), also referred to as “purchase accounting.” Under the asset acquisition method of accounting, acquiring assets in groups not only requires ascertaining the cost of the asset (or net assets), but also allocating that cost to the individual assets (or individual assets and liabilities) that make up the group. Per ASC Topic 805, assets are recognized based on their cost to the acquiring entity, which generally includes transaction costs of the asset acquisition, and no gain or loss is recognized unless the fair value of non-cash assets given as consideration differs from the assets carrying amounts on the acquiring entity’s books. The cost of the group of assets acquired in an asset acquisition is allocated to the individual assets acquired or liabilities assumed based on the relative fair values of net identifiable assets acquired other than “non-qualifying” assets (for example cash) and does not give rise to goodwill. To the extent that the consideration paid to GCIC or GBDC 3’s stockholders exceeded the relative fair values of the net identifiable assets of GCIC or GBDC 3 acquired other than “non-qualifying” assets, any such premium paid by the Company was further allocated to the cost of the GCIC or GBDC 3 assets acquired by the Company pro-rata to their relative fair value, other than “non-qualifying” assets. As both GCIC and GBDC 3 did not have any “qualifying” assets at the time of acquisition, the premium was allocated to “non-qualifying” assets, which are GCIC and GBDC 3’s investments in loans and equity securities, including its investment in GCIC SLF. Immediately following the acquisitions of GCIC and GBDC 3, the Company recorded its assets at their respective fair values and, as a result, the purchase premium allocated to the cost basis of the GCIC and GBDC 3 assets acquired was immediately recognized as unrealized depreciation on the Company's Consolidated Statement of Operations. The purchase premium allocated to investments in loan securities will amortize over the life of the loans through interest income, with a corresponding reversal of the unrealized depreciation on the loans acquired from GCIC and GBDC 3 through their ultimate disposition.The purchase premium allocated to investments in equity securities will not amortize over the life of the equity securities through interest income and, assuming no subsequent change to the fair value of the equity securities acquired from GCIC or GBDC 3 and disposition of such equity securities at fair value, the Company will recognize a realized loss with a corresponding reversal of the unrealized depreciation upon disposition of the equity securities acquired from GCIC or GBDC 3.
Income taxes	Income taxes: The Company has elected to be treated as a RIC under Subchapter M of the Code and operates in a manner so as to qualify for the tax treatment applicable to RICs. In order to qualify and be subject to tax as a RIC, among other things, the Company is required to meet certain source of income and asset diversification requirements and timely distribute dividends for U.S. federal income tax purposes to its stockholders of an amount generally at least equal to 90% of investment company taxable income, as defined by the Code and determined without regard to any deduction for dividends paid, for each tax year. The Company has made, and intends to continue to make, the requisite distributions to its stockholders, which will generally relieve the Company from U.S. federal income taxes with respect to all income distributed to its stockholders. Depending on the level of taxable income earned in a tax year, the Company can determine to retain taxable income in excess of current year dividend distributions and distribute such taxable income in the next tax year. The Company may then be required to incur a 4% excise tax on such income. To the extent that the Company determines that its estimated current year annual taxable income, determined on a calendar year basis, could exceed estimated current calendar year dividend distributions, the Company accrues excise tax, if any, on estimated excess taxable income as taxable income is earned. For the three and nine months ended June 30, 2024, $125 and $1,124, respectively, was recorded for U.S. federal excise tax. For the three months ended June 30, 2023, the company did not record any U.S. federal excise tax. For the nine months ended June 30, 2023, $2,432 was recorded for U.S. federal excise tax. The Company accounts for income taxes in conformity with ASC Topic 740 — Income Taxes (“ASC Topic 740”). ASC Topic 740 provides guidelines for how uncertain tax positions should be recognized, measured, presented and disclosed in the consolidated financial statements. ASC Topic 740 requires the evaluation of tax positions taken in the course of preparing the Company’s tax returns to determine whether the tax positions are “more-likely-than-not” to be sustained by the applicable tax authority. Tax benefits of positions not deemed to meet the more-likely-than-not threshold would be recorded as a tax expense or tax benefit in the current year. It is the Company’s policy to recognize accrued interest and penalties related to uncertain tax benefits in income tax expense. There were no material unrecognized tax benefits or unrecognized tax liabilities related to uncertain income tax positions through June 30, 2024. The Company's tax returns for the 2021 through 2023 tax years remain subject to examination by U.S. federal and most state tax authorities. Certain of the Company's consolidated subsidiaries are subject to U.S. federal and state corporate-level income taxes. Income tax expense, if any, is included under the income category for which it applies in the Consolidated Statements of Operations.
Dividends and distributions	Dividends and distributions: Dividends and distributions to common stockholders are recorded on the ex-dividend date. The amount to be paid out as a dividend or distribution is determined by the Board each quarter and is generally based upon the earnings estimated by management. Net realized capital gains, if any, are distributed at least annually, although the Company can retain such capital gains for investment in its discretion. The Company has adopted a dividend reinvestment plan (“DRIP”) that provides for reinvestment of any distributions the Company declares in cash on behalf of its stockholders, unless a stockholder elects to receive cash. As a result, if the Board authorizes and the Company declares a cash distribution, then stockholders who participate in the DRIP will have their cash distribution reinvested in additional shares of the Company’s common stock, rather than receiving the cash distribution. The Company expects to use newly issued shares under the guidelines of the DRIP if the Company’s shares are trading at a premium to net asset value. The Company can purchase shares in the open market in connection with the obligations under the plan, and in particular, if the Company’s shares are trading at a significant discount to net asset value (“NAV”) and the Company is otherwise permitted under applicable law to purchase such shares, the Company intends to purchase shares in the open market in connection with any obligations under the DRIP. In the event the market price per share of the Company’s common stock on the date of a distribution exceeds the most recently computed NAV per share of the common stock, the Company will issue shares of common stock to participants in the DRIP at the greater of the most recently computed NAV per share of common stock or 95% of the current market price per share of common stock (or such lesser discount to the current market price per share that still exceeds the most recently computed NAV per share of common stock).
Share repurchase plan and Deferred offering costs	Share repurchase plan: The Company has a share repurchase program (the “Program”) which allows the Company to repurchase the Company’s outstanding common stock on the open market at prices below the Company’s NAV as reported in its most recently published consolidated financial statements. The Board reapproved the Program in August 2024 and the Program is implemented at the discretion of management. Shares can be purchased from time to time at prevailing market prices, through open market transactions, including block transactions. Deferred offering costs: Deferred offering costs consist of fees paid in relation to legal, accounting, regulatory and printing work completed in preparation of equity offerings. Deferred offering costs are charged against the proceeds from equity offerings when received. These amounts are included in other assets on the Consolidated Statements of Financial Condition.
Equity Distribution Agreement	Equity Distribution Agreement: On October 6, 2023, the Company entered into a new equity distribution agreement (the “2023 Equity Distribution Agreement”), by and among the Company, the Investment Adviser, Golub Capital LLC and Keefe, Bruyette & Woods, Inc. and Regions Securities LLC (the “Placement Agents”), in connection with the sale by the Company of shares of its common stock, having an aggregate offering price of up to $250,000, in an “at the market offering,” in amounts and at times to be determined by the Company. Actual sales, if any, will depend on a variety of factors to be determined by the Company from time to time, including, among others, market conditions and the market price of the Company’s common stock. The 2023 Equity Distribution Agreement provides that the Company may offer and sell shares from time to time through, or to, the Placement Agents, or to it. Sales of the shares, if any, may be made in negotiated transactions or transactions that are deemed to be “at the market,” as defined in Rule 415 under the Securities Act of 1933, as amended, including sales made directly on The Nasdaq Global Select Market or any similar securities exchange or sales made to or through a market maker other than on a securities exchange, at prices related to the prevailing market prices or at negotiated prices. Pursuant to the terms of the 2023 Equity Distribution Agreement, the Placement Agents will receive a commission from the Company of up to 1.50% of the gross sales price of any shares sold through the Placement Agents under the 2023 Equity Distribution Agreement. Offering costs for the 2023 Equity Distribution Agreement are charged against the proceeds from equity offerings when proceeds are received.
Deferred debt issuance costs	Deferred debt issuance costs: Deferred debt issuance costs represent fees and other direct incremental costs incurred in connection with the Company’s borrowings.These amounts are amortized and included in interest expense in the Consolidated Statements of Operations over the estimated average life of the borrowings.
Fair value measurement	The Company follows ASC Topic 820 for measuring fair value. Fair value is the price that would be received in the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Where available, fair value is based on observable market prices or parameters, or derived from such prices or parameters. Where observable prices or inputs are not available, valuation models are applied. These valuation models involve some level of management estimation and judgment, the degree of which is dependent on the price transparency for the assets or liabilities or market and the assets’ or liabilities’ complexity. The Company’s fair value analysis includes an analysis of the value of any unfunded loan commitments. Assets and liabilities are categorized for disclosure purposes based upon the level of judgment associated with the inputs used to measure their value. The valuation hierarchical levels are based upon the transparency of the inputs to the valuation of the asset or liability as of the measurement date. The three levels are defined as follows: Level 1: Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2: Inputs include quoted prices for similar assets or liabilities in active markets and inputs that are observable for the assets or liabilities, either directly or indirectly, for substantially the full term of the assets or liabilities. Level 3: Inputs include significant unobservable inputs for the assets or liabilities and include situations where there is little, if any, market activity for the assets or liabilities. The inputs into the determination of fair value are based upon the best information available and require significant management judgment or estimation. In certain cases, the inputs used to measure fair value fall into different levels of the fair value hierarchy. In such cases, an asset’s or a liability’s categorization within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability. The Company assesses the levels of assets and liabilities at each measurement date, and transfers between levels are recognized on the actual date of the event or change in circumstances that caused the transfers. There were no transfers among Level 1, 2 and 3 of the fair value hierarchy for assets and liabilities during the three and nine months ended June 30, 2024 and 2023. The following section describes the valuation techniques used by the Company to measure different assets and liabilities at fair value and includes the level within the fair value hierarchy in which the assets and liabilities are categorized. Investments Level 1 investments are valued using quoted market prices. Level 2 investments are valued using market consensus prices that are corroborated by observable market data and quoted market prices for similar assets and liabilities. Level 3 investments are valued at fair value as determined in good faith by the Board, based on input of management, the audit committee and independent valuation firms that have been engaged at the direction of the Board to assist in the valuation of each portfolio investment without a readily available market quotation at least once during a trailing twelve-month period under a valuation policy and a consistently applied valuation process. This valuation process is conducted at the end of each fiscal quarter, with approximately 25% (based on the number of portfolio companies) of the Company’s valuations of debt and equity investments without readily available market quotations subject to review by an independent valuation firm. All investments as of June 30, 2024 and September 30, 2023, with the exception of one portfolio company investment (Level 1 investments), were valued using Level 3 inputs. As of June 30, 2024 and September 30, 2023, all money market funds included in cash and cash equivalents and restricted cash and cash equivalents were valued using Level 1 inputs and all forward currency contracts and interest rate swaps were valued using Level 2 inputs. When determining fair value of Level 3 debt and equity investments, the Company takes into account the following factors, where relevant: the enterprise value of a portfolio company, the nature and realizable value of any collateral, the portfolio company’s ability to make payments and its earnings and discounted cash flows, the markets in which the portfolio company does business, comparisons to publicly traded securities, and changes in the interest rate environment and the credit markets generally that affect the price at which similar investments are made and other relevant factors. The primary method for determining enterprise value uses a multiple analysis whereby appropriate multiples are applied to the portfolio company’s net income before net interest expense, income tax expense, depreciation and amortization (“EBITDA”). A portfolio company’s EBITDA can include pro forma adjustments for items such as acquisitions, divestitures, or expense reductions. The enterprise value analysis is performed to determine the value of equity investments and to determine if debt investments are credit impaired. If debt investments are credit impaired, the Company will use the enterprise value analysis or a liquidation basis analysis to determine fair value. For debt investments that are not determined to be credit impaired, the Company uses a market interest rate yield analysis to determine fair value. In addition, for certain debt investments, the Company bases its valuation on indicative bid and ask prices provided by an independent third party pricing service. Bid prices reflect the highest price that the Company and others may be willing to pay. Ask prices represent the lowest price that the Company and others may be willing to accept. The Company generally uses the midpoint of the bid/ask range as its best estimate of fair value of such investment. Due to the inherent uncertainty of determining the fair value of Level 3 investments that do not have a readily available market value, the fair value of the investments may differ significantly from the values that would have been used had a ready market existed for such investments and may differ materially from the values that are ultimately received or settled. Further, such investments are generally subject to legal and other restrictions or otherwise are less liquid than publicly traded instruments. If the Company were required to liquidate a portfolio investment in a forced or liquidation sale, the Company could realize significantly less than the value at which such investment had previously been recorded. The Company’s investments are subject to market risk. Market risk is the potential for changes in the value due to market changes. Market risk is directly impacted by the volatility and liquidity in the markets in which the investments are traded.

Significant Accounting Policies and Recent Accounting Updates (Policies)

9 Months Ended

Jun. 30, 2024

Basis of presentation: The Company is an investment company as defined in the accounting and reporting guidance under Accounting Standards Codification (“ASC”) Topic 946 — Financial Services — Investment Companies (“ASC Topic 946”).

The accompanying unaudited interim consolidated financial statements of the Company and related financial information have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) as established by the Financial Accounting Standards Board (“FASB”) for interim financial information and pursuant to the requirements for reporting on Form 10-Q and Articles 6, 10 and 12 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for annual financial statements. In the opinion of management, the consolidated financial statements reflect all adjustments and reclassifications consisting solely of normal accruals that are necessary for the fair presentation of financial results as of and for the periods presented. All intercompany balances and transactions have been eliminated.

Certain prior period amounts have been reclassified to conform to the current period presentation. The unaudited interim consolidated financial statements and notes thereto should be read in conjunction with the financial statements and notes thereto in the Company’s Form 10-K for the year ended September 30, 2023, as filed with the U.S. Securities and Exchange Commission (the “SEC”).

Fair value of financial instruments

Fair value of financial instruments: The Company applies fair value to all of its financial instruments in accordance with ASC Topic 820 — Fair Value Measurement (“ASC Topic 820”). ASC Topic 820 defines fair value, establishes a framework used to measure fair value and requires disclosures for fair value measurements. In accordance with ASC Topic 820, the Company has categorized its financial instruments carried at fair value, based on the priority of the valuation technique, into a three-level fair value hierarchy. Fair value is a market-based measure considered from the perspective of the market participant who holds the financial instrument rather than an entity-specific measure. Therefore, when market assumptions are not readily available, the Company’s own assumptions are set to reflect those that management believes market participants would use in pricing the financial instrument at the measurement date.

The availability of observable inputs can vary depending on the financial instrument and is affected by a wide variety of factors, including, for example, the type of product, whether the product is new, whether the product is traded on an active exchange or in the secondary market and the current market conditions. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for financial instruments classified as Level 3.

Any changes to the valuation methodology are reviewed by management and the Company’s board of directors (the “Board”) to confirm that the changes are appropriate. As markets change, new products develop and the pricing for products becomes more or less transparent, the Company will continue to refine its valuation methodologies.

Use of estimates

Use of estimates: The preparation of the unaudited interim consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Consolidation

Consolidation: As provided under Regulation S-X and ASC Topic 946, the Company will generally not consolidate its investment in a company other than an investment company subsidiary or a controlled operating company whose business consists of providing services to the Company.

Assets related to transactions that do not meet ASC Topic 860 requirements for accounting sale treatment are reflected in the Company’s Consolidated Statements of Financial Condition as investments. Those assets are owned by special purpose entities, including BDC Holdings, 2018 Issuer, Funding II, GCIC Holdings, GCIC 2018 Issuer, GBDC 3 Holdings, GBDC 3 Funding, GBDC 3 2021 Issuer, GBDC 3 2022 Issuer and the GBDC 3 2022-2 Issuer, that are consolidated in the Company’s consolidated financial statements. The creditors of the special purpose entities have received security interests in such assets and such assets are not intended to be available to the creditors of GBDC (or any affiliate of GBDC).

Cash and cash equivalents and foreign currencies

Cash and cash equivalents and foreign currencies: Cash and cash equivalents and foreign currencies are highly liquid investments with an original maturity of three months or less at the date of acquisition. The Company deposits its cash in financial institutions and, at times, such balances exceed the Federal Deposit Insurance Corporation insurance limits.

Restricted cash and cash equivalents and restricted foreign currencies

Restricted cash and cash equivalents and restricted foreign currencies: Restricted cash and cash equivalents and restricted foreign currencies include amounts that are collected and are held by trustees who have been appointed as custodians of the assets securing certain of the Company’s financing transactions. Restricted cash and cash equivalents and restricted foreign currencies are held by the trustees for payment of interest expense and principal on the outstanding borrowings or reinvestment into new assets.

Foreign currency translation

Foreign currency translation: The Company’s books and records are maintained in U.S. dollars. Any foreign currency amounts are translated into U.S. dollars. Non-U.S. dollar transactions during the period are valued at the prevailing spot rates on the applicable transaction date and the related assets and liabilities are revalued at the prevailing spot rates as of period-end.

Net assets and fair values are presented based on the applicable foreign exchange rates and fluctuations arising from the translation of assets and liabilities are included with the net change in unrealized appreciation (depreciation) on translation of assets and liabilities in foreign currencies on the Consolidated Statements of Operations.

Foreign security and currency transactions involve certain considerations and risks not typically associated with investing in U.S. companies. These risks include, but are not limited to, currency fluctuations and revaluations and future adverse political, social and economic developments, which could cause investments in foreign markets to be less liquid and prices more volatile than those of comparable U.S. companies or U.S. government securities.

Derivative Instruments

Derivative Instruments:

The Company follows the guidance in ASC Topic 815, Derivatives and Hedging (“ASC Topic 815”), when accounting for derivative instruments.

Forward currency contracts: A forward currency contract is an obligation between two parties to purchase or sell a specific currency for an agreed-upon price at a future date. The Company utilized forward currency contracts to economically hedge the currency exposure associated with certain foreign-denominated investments. The use of forward currency contracts does not eliminate fluctuations in the price of the underlying securities the Company owns or intends to acquire but establishes a rate of exchange in advance. Fluctuations in the value of these contracts are measured by the difference in the exchange rates on the contract date and reporting date and are recorded as unrealized appreciation (depreciation) until the contracts are closed. When the contracts are closed, realized gains (losses) are recorded. Realized gains (losses) and unrealized appreciation (depreciation) on the contracts are included in the Consolidated Statements of Operations. Unrealized appreciation (depreciation) on forward currency contracts is recorded on the Consolidated Statements of Financial Condition by counterparty on a net basis, not taking into account collateral posted which is recorded separately, if applicable.

The primary risks associated with forward currency contracts include failure of the counterparty to meet the terms of the contract and the value of the foreign currency changing unfavorably. These risks can exceed the amounts reflected in the Consolidated Statements of Financial Condition.

Refer to Note 5 for more information regarding the forward currency contracts.

Interest rate swaps: The Company designated interest rate swaps as the hedging instrument in qualifying fair value hedge accounting relationships, and as a result, the change in fair value of the hedging instruments and hedged items are recorded in interest expense and recognized as components of “interest expense” in the Company’s Consolidated Statement of Operations. The fair value of the interest rate swaps is included as a component of “Accounts payable and other liabilities” on the Company's Consolidated Statements of Financial Condition. Refer to Note 5 for more information regarding the interest rate swaps.

Revenue recognition

Revenue recognition:

Investments and related investment income: Interest income is accrued based upon the outstanding principal amount and contractual interest terms of debt investments.

Loan origination fees, original issue discount and market discount or premium are capitalized, and the Company accretes or amortizes such amounts over the life of the loan as interest income.For investments with contractual payment-in-kind (“PIK”) interest, which represents contractual interest accrued and added to the principal balance that generally becomes due at maturity, the Company will not accrue PIK interest if the portfolio company valuation indicates that the PIK interest is not collectible.In addition, the Company generates revenue in the form of amendment, structuring or due diligence fees, fees for providing managerial assistance, consulting fees, administrative agent fees, and prepayment premiums on loans. The Company records these fees as fee income when earned.

Dividend income on equity securities is recorded as dividend income on an accrual basis to the extent that such amounts are payable by the portfolio company and are expected to be collected. The Company has certain preferred equity securities in the portfolio that contain a PIK dividend provision that are accrued and recorded as income at the contractual rates, if deemed collectible. The accrued PIK and non-cash dividends are capitalized to the cost basis of the preferred equity security and are generally collected when redeemed by the issuer.

Dividend income on common equity securities is recorded on the record date for private portfolio companies or on the ex-dividend date for publicly traded portfolio companies. Each distribution received from limited liability company (“LLC”) and limited partnership (“LP”) investments is evaluated to determine if the distribution should be recorded as dividend income or a return of capital. Generally, the Company will not record distributions from equity investments in LLCs and LPs as dividend income unless there are sufficient accumulated tax-basis earnings and profits in the LLC or LP prior to the distribution. Distributions that are classified as a return of capital are recorded as a reduction in the cost basis of the investment.

Investment transactions

Investment transactions are accounted for on a trade-date basis. Realized gains or losses on investments are measured by the difference between the net proceeds from the disposition and the amortized cost basis of investment, without regard to unrealized gains or losses previously recognized. The Company reports current period changes in fair value of investments that are measured at fair value as a component of the net change in unrealized appreciation (depreciation) on investment transactions in the Consolidated Statements of Operations.

Non-accrual loans

Non-accrual loans: A loan can be left on accrual status during the period the Company is pursuing repayment of the loan. Management reviews all loans that become 90 days or more past due on principal and interest, or when there is reasonable doubt that principal or interest will be collected, for possible placement on non-accrual status. When a loan is placed on non-accrual status, unpaid interest credited to income is reversed. Additionally, any original issue discount and market discount are no longer accreted to interest income as of the date the loan is placed on non-accrual status. Interest payments received on non-accrual loans are recognized as income or applied to principal depending upon management’s judgment. Non-accrual loans are restored to accrual status when past due principal and interest is paid and, in management’s judgment, payments are likely to remain current.

Purchase accounting

Purchase accounting: Pursuant to the GCIC Merger Agreement, the GCIC Merger Sub was first merged with and into GCIC, with GCIC as the surviving company (the “Initial GCIC Merger”), and, immediately following the Initial GCIC Merger, GCIC was then merged with and into the Company, with the Company as the surviving company (the Initial GCIC Merger and the subsequent merger, collectively, the “GCIC Merger”). Pursuant to the GBDC 3 Merger Agreement, the GBDC 3 Merger Sub was first merged with and into GBDC 3, with GBDC 3 as the surviving company in the Initial GBDC 3 Merger and, immediately following the Initial GBDC 3 Merger, GBDC 3 was then merged with and into the Company, with the Company as the surviving company. The GCIC Merger and the GBDC 3 Merger were accounted for under the asset acquisition method of accounting in accordance with ASC 805 — Business Combinations — Related Issues (“ASC Topic 805”), also referred to as “purchase accounting.” Under the asset acquisition method of accounting, acquiring assets in groups not only requires ascertaining the cost of the asset (or net assets), but also allocating that cost to the individual assets (or individual assets and liabilities) that make up the group. Per ASC Topic 805, assets are recognized based on their cost to the acquiring entity, which generally includes transaction costs of the asset acquisition, and no gain or loss is recognized unless the fair value of non-cash assets given as consideration differs from the assets carrying amounts on the acquiring entity’s books.

The cost of the group of assets acquired in an asset acquisition is allocated to the individual assets acquired or liabilities assumed based on the relative fair values of net identifiable assets acquired other than “non-qualifying” assets (for example cash) and does not give rise to goodwill. To the extent that the consideration paid to GCIC or GBDC 3’s stockholders exceeded the relative fair values of the net identifiable assets of GCIC or GBDC 3 acquired other than “non-qualifying” assets, any such premium paid by the Company was further allocated to the cost of the GCIC or GBDC 3 assets acquired by the Company pro-rata to their relative fair value, other than “non-qualifying” assets. As both GCIC and GBDC 3 did not have any “qualifying” assets at the time of acquisition, the premium was allocated to “non-qualifying” assets, which are GCIC and GBDC 3’s investments in loans and equity securities, including its investment in GCIC SLF. Immediately following the acquisitions of GCIC and GBDC 3, the Company recorded its assets at their respective fair values and, as a result, the purchase premium allocated to the cost basis of the GCIC and GBDC 3 assets acquired was immediately recognized as unrealized depreciation on the Company's Consolidated Statement of Operations. The purchase premium allocated to investments in loan securities will amortize over the life of the loans through interest income, with a corresponding reversal of the unrealized depreciation on the loans acquired from GCIC and GBDC 3 through their ultimate disposition.The purchase premium allocated to investments in equity securities will not amortize over the life of the equity securities through interest income and, assuming no subsequent change to the fair value of the equity securities acquired from GCIC or GBDC 3 and disposition of such equity securities at fair value, the Company will recognize a realized loss with a corresponding reversal of the unrealized depreciation upon disposition of the equity securities acquired from GCIC or GBDC 3.

Income taxes

Income taxes: The Company has elected to be treated as a RIC under Subchapter M of the Code and operates in a manner so as to qualify for the tax treatment applicable to RICs. In order to qualify and be subject to tax as a RIC, among other things, the Company is required to meet certain source of income and asset diversification requirements and timely distribute dividends for U.S. federal income tax purposes to its stockholders of an amount generally at least equal to 90% of investment company taxable income, as defined by the Code and determined without regard to any deduction for dividends paid, for each tax year. The Company has made, and intends to continue to make, the requisite distributions to its stockholders, which will generally relieve the Company from U.S. federal income taxes with respect to all income distributed to its stockholders.

Depending on the level of taxable income earned in a tax year, the Company can determine to retain taxable income in excess of current year dividend distributions and distribute such taxable income in the next tax year. The Company may then be required to incur a 4% excise tax on such income. To the extent that the Company determines that its estimated current year annual taxable income, determined on a calendar year basis, could exceed estimated current calendar year dividend distributions, the Company accrues excise tax, if any, on estimated excess taxable income as taxable income is earned. For the three and nine months ended June 30, 2024, $125 and $1,124, respectively, was recorded for U.S. federal excise tax. For the three months ended June 30, 2023, the company did not record any U.S. federal excise tax. For the nine months ended June 30, 2023, $2,432 was recorded for U.S. federal excise tax.

The Company accounts for income taxes in conformity with ASC Topic 740 — Income Taxes (“ASC Topic 740”). ASC Topic 740 provides guidelines for how uncertain tax positions should be recognized, measured, presented and disclosed in the consolidated financial statements. ASC Topic 740 requires the evaluation of tax positions taken in the course of preparing the Company’s tax returns to determine whether the tax positions are “more-likely-than-not” to be sustained by the applicable tax authority. Tax benefits of positions not deemed to meet the more-likely-than-not threshold would be recorded as a tax expense or tax benefit in the current year. It is the Company’s policy to recognize accrued interest and penalties related to uncertain tax benefits in income tax expense. There were no material unrecognized tax benefits or unrecognized tax liabilities related to uncertain income tax positions through June 30, 2024. The Company's tax returns for the 2021 through 2023 tax years remain subject to examination by U.S. federal and most state tax authorities.

Certain of the Company's consolidated subsidiaries are subject to U.S. federal and state corporate-level income taxes. Income tax expense, if any, is included under the income category for which it applies in the Consolidated Statements of Operations.

Dividends and distributions

Dividends and distributions: Dividends and distributions to common stockholders are recorded on the ex-dividend date. The amount to be paid out as a dividend or distribution is determined by the Board each quarter and is generally based upon the earnings estimated by management. Net realized capital gains, if any, are distributed at least annually, although the Company can retain such capital gains for investment in its discretion.

The Company has adopted a dividend reinvestment plan (“DRIP”) that provides for reinvestment of any distributions the Company declares in cash on behalf of its stockholders, unless a stockholder elects to receive cash. As a result, if the Board authorizes and the Company declares a cash distribution, then stockholders who participate in the DRIP will have their cash distribution reinvested in additional shares of the Company’s common stock, rather than receiving the cash distribution. The Company expects to use newly issued shares under the guidelines of the DRIP if the Company’s shares are trading at a premium to net asset value. The Company can purchase shares in the open market in connection with the obligations under the plan, and in particular, if the Company’s shares are trading at a significant discount to net asset value (“NAV”) and the Company is otherwise permitted under applicable law to purchase such shares, the Company intends to purchase shares in the open market in connection with any obligations under the DRIP.

In the event the market price per share of the Company’s common stock on the date of a distribution exceeds the most recently computed NAV per share of the common stock, the Company will issue shares of common stock to participants in the DRIP at the greater of the most recently computed NAV per share of common stock or 95% of the current market price per share of common stock (or such lesser discount to the current market price per share that still exceeds the most recently computed NAV per share of common stock).

Share repurchase plan and Deferred offering costs

Share repurchase plan: The Company has a share repurchase program (the “Program”) which allows the Company to repurchase the Company’s outstanding common stock on the open market at prices below the Company’s NAV as reported in its most recently published consolidated financial statements. The Board reapproved the Program in August 2024 and the Program is implemented at the discretion of management. Shares can be purchased from time to time at prevailing market prices, through open market transactions, including block transactions. Deferred offering costs: Deferred offering costs consist of fees paid in relation to legal, accounting, regulatory and printing work completed in preparation of equity offerings. Deferred offering costs are charged against the proceeds from equity offerings when received. These amounts are included in other assets on the Consolidated Statements of Financial Condition.

Equity Distribution Agreement

Equity Distribution Agreement: On October 6, 2023, the Company entered into a new equity distribution agreement (the “2023 Equity Distribution Agreement”), by and among the Company, the Investment Adviser, Golub Capital LLC and Keefe, Bruyette & Woods, Inc. and Regions Securities LLC (the “Placement Agents”), in connection with the sale by the Company of shares of its common stock, having an aggregate offering price of up to $250,000, in an “at the market offering,” in amounts and at times to be determined by the Company. Actual sales, if any, will depend on a variety of factors to be determined by the Company from time to time, including, among others, market conditions and the market price of the Company’s common stock. The 2023 Equity Distribution Agreement provides that the Company may offer and sell shares from time to time through, or to, the Placement Agents, or to it. Sales of the shares, if any, may be made in negotiated transactions or transactions that are deemed to be “at the market,” as defined in Rule 415 under the Securities Act of 1933, as amended, including sales made directly on The Nasdaq Global Select Market or any similar securities exchange or sales made to or through a market maker other than on a securities exchange, at prices related to the prevailing market prices or at negotiated prices. Pursuant to the terms of the 2023 Equity Distribution Agreement, the Placement Agents will receive a commission from the Company of up to 1.50% of the gross sales price of any shares sold through the Placement Agents under the 2023 Equity Distribution Agreement. Offering costs for the 2023 Equity Distribution Agreement are charged against the proceeds from equity offerings when proceeds are received.

Deferred debt issuance costs

Deferred debt issuance costs: Deferred debt issuance costs represent fees and other direct incremental costs incurred in connection with the Company’s borrowings.These amounts are amortized and included in interest expense in the Consolidated Statements of Operations over the estimated average life of the borrowings.

Fair value measurement

The Company follows ASC Topic 820 for measuring fair value. Fair value is the price that would be received in the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Where available, fair value is based on observable market prices or parameters, or derived from such prices or parameters. Where observable prices or inputs are not available, valuation models are applied. These valuation models involve some level of management estimation and judgment, the degree of which is dependent on the price transparency for the assets or liabilities or market and the assets’ or liabilities’ complexity. The Company’s fair value analysis includes an analysis of the value of any unfunded loan commitments. Assets and liabilities are categorized for disclosure purposes based upon the level of judgment associated with the inputs used to measure their value. The valuation hierarchical levels are based upon the transparency of the inputs to the valuation of the asset or liability as of the measurement date. The three levels are defined as follows:

Level 1: Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 2: Inputs include quoted prices for similar assets or liabilities in active markets and inputs that are observable for the assets or liabilities, either directly or indirectly, for substantially the full term of the assets or liabilities.

Level 3: Inputs include significant unobservable inputs for the assets or liabilities and include situations where there is little, if any, market activity for the assets or liabilities. The inputs into the determination of fair value are based upon the best information available and require significant management judgment or estimation.

In certain cases, the inputs used to measure fair value fall into different levels of the fair value hierarchy. In such cases, an asset’s or a liability’s categorization within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability. The Company assesses the levels of assets and liabilities at each measurement date, and transfers between levels are recognized on the actual date of the event or change in circumstances that caused the transfers. There were no transfers among Level 1, 2 and 3 of the fair value hierarchy for assets and liabilities during the three and nine months ended June 30, 2024 and 2023. The following section describes the valuation techniques used by the Company to measure different assets and liabilities at fair value and includes the level within the fair value hierarchy in which the assets and liabilities are categorized.

Investments

Level 1 investments are valued using quoted market prices. Level 2 investments are valued using market consensus prices that are corroborated by observable market data and quoted market prices for similar assets and liabilities. Level 3 investments are valued at fair value as determined in good faith by the Board, based on input of management, the audit committee and independent valuation firms that have been engaged at the direction of the Board to assist in the valuation of each portfolio investment without a readily available market quotation at least once during a trailing twelve-month period under a valuation policy and a consistently applied valuation process. This valuation process is conducted at the end of each fiscal quarter, with approximately 25% (based on the number of portfolio companies) of the Company’s valuations of debt and equity investments without readily available market quotations subject to review by an independent valuation firm. All investments as of June 30, 2024 and September 30, 2023, with the exception of one portfolio company investment (Level 1 investments), were valued using Level 3 inputs. As of June 30, 2024 and September 30, 2023, all money market funds included in cash and cash equivalents and restricted cash and cash equivalents were valued using Level 1 inputs and all forward currency contracts and interest rate swaps were valued using Level 2 inputs.

When determining fair value of Level 3 debt and equity investments, the Company takes into account the following factors, where relevant: the enterprise value of a portfolio company, the nature and realizable value of any collateral, the portfolio company’s ability to make payments and its earnings and discounted cash flows, the markets in which the portfolio company does business, comparisons to publicly traded securities, and changes in the interest rate environment and the credit markets generally that affect the price at which similar investments are made and other relevant factors. The primary method for determining enterprise value uses a multiple analysis whereby appropriate multiples are applied to the portfolio company’s net income before net interest expense, income tax expense, depreciation and amortization (“EBITDA”). A portfolio company’s EBITDA can include pro forma adjustments for items such as acquisitions, divestitures, or expense reductions. The enterprise value analysis is performed to determine the value of equity investments and to determine if debt investments are credit impaired. If debt investments are credit impaired, the Company will use the enterprise value analysis or a liquidation basis analysis to determine fair value. For debt investments that are not determined to be credit impaired, the Company uses a market interest rate yield analysis to determine fair value.

In addition, for certain debt investments, the Company bases its valuation on indicative bid and ask prices provided by an independent third party pricing service. Bid prices reflect the highest price that the Company and others may be willing to pay. Ask prices represent the lowest price that the Company and others may be willing to accept. The Company generally uses the midpoint of the bid/ask range as its best estimate of fair value of such investment.

Due to the inherent uncertainty of determining the fair value of Level 3 investments that do not have a readily available market value, the fair value of the investments may differ significantly from the values that would have been used had a ready market existed for such investments and may differ materially from the values that are ultimately received or settled. Further, such investments are generally subject to legal and other restrictions or otherwise are less liquid than publicly traded instruments. If the Company were required to liquidate a portfolio investment in a forced or liquidation sale, the Company could realize significantly less than the value at which such investment had previously been recorded. The Company’s investments are subject to market risk. Market risk is the potential for changes in the value due to market changes. Market risk is directly impacted by the volatility and liquidity in the markets in which the investments are traded.