Golub Capital Private Income Fund S

Item 3.02. Unregistered Sales of Equity Securities. As of September 1, 2026, Golub Capital Private Income Fund S (the “Fund”) sold unregistered common shares of beneficial interest, par value $0.01 (the “Common Shares”), based on the Fund’s net asset value (“NAV”) per Common Share as of August 31, 2026, pursuant to subscription agreements entered into by the Fund and its investors. The offer and sale of the Common Shares were exempt from the registration requirements of the Securities Act of 1933, as amended, pursuant to Section 4(a)(2), Regulation D, and/or Regulation S thereunder. The following table details the amount of Common Shares sold and consideration therefor: Date of Unregistered Sale Amount of Common Shares NAV per Common Share Consideration(1) ────────────────────────────────────────────────────────────────────────────────────────────────────────── As of September 1, 2026 81,237 $24.25 $1,970,000 (1) No underwriting discounts or commissions have been or will be paid in connection with the sale of such Common Shares. Although the Fund does not charge investors any upfront placement or other fees with respect to the Common Shares, investors who purchase Common Shares through certain financial intermediaries may be directly charged transaction or other fees by such intermediaries, including upfront placement fees or brokerage commissions, in such amounts as the financial intermediaries may determine, provided that selling agents limit such charges to 3.5% of NAV for Common Shares.

Item 7.01. Regulation FD Disclosures. September 2026 Distribution As previously disclosed, on July 31, 2026, the Fund declared a regular distribution for its Common Shares in the amount per share set forth below: Gross Shareholder Net Distribution Servicing and/or Distribution Fee(1) Distribution ────────────────────────────────────────────────────────────────────────────────────────────────────────────── September 2026 Common Shares Distribution $0.1667 $0.0169 $0.1498 (1) Amount is estimated utilizing the August 31, 2026 NAV per Common Share. The September net distribution for Common Shares is payable to shareholders of record as of the open of business on September 30, 2026 and will be paid on or around October 30, 2026. This distribution will be paid in cash or reinvested in Common Shares of the Fund for shareholders participating in the Fund’s distribution reinvestment plan.

Item 8.01. Other Events. Portfolio and Business Commentary As of August 31, 2026, the Fund had investments in 171 portfolio companies with total fair value of approximately $249 million. As of August 31, 2026, the Fund’s investments as a percentage of the portfolio at fair value were comprised of the following: Investment Type As of August 31, 2026 ────────────────────────────────────────────────── First Lien Senior Secured 98% Junior Debt 0%* Equity 2% * Represents an amount less than 1%. As of August 31, 2026, approximately 100% of the debt investments in the Fund’s portfolio, based on fair value, were floating rates and three debt investments representing less than 1% had a fixed interest rate. As of August 31, 2026, the ten largest industries in which the Fund was invested, represented as a percentage of fair value, were as follows: Industry As of August 31, 2026 ──────────────────────────────────────────────────────── Software 25% Insurance 10% Healthcare Providers & Services 7% Hotels, Restaurants & Leisure 6% Healthcare Equipment & Supplies 5% Automobiles 5% Commercial Services & Supplies 5% Containers & Packaging 4% Healthcare Technology 4% Professional Services 4% As of August 31, 2026, the Fund’s aggregate NAV was approximately $121 million, the fair value of its portfolio investments was approximately $249 million, and it had approximately $141 million of debt outstanding. As of August 31, 2026, the Fund’s debt-to-equity leverage ratio was 1.17x and GAAP debt-to-equity ratio, net, which reduces total debt by cash and cash equivalents and foreign currencies was 1.13x. Net Asset Value The NAV per Common Share of the Fund as of August 31, 2026, as determined in accordance with the Fund’s valuation policy and procedures, is set forth below: NAV per Common Share as of August 31, 2026 ──────────────────────────────────────────── Common Shares $24.25 SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, Golub Capital Private Income Fund S has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. GOLUB CAPITAL PRIVATE INCOME FUND S Date: September 25, 2026 By: /s/ Paul Solini Name: Paul Solini Title: Chief Accounting Officer