ONE Gas, Inc. 8-KCurrent Reports (8-K / ad hoc)

Changes / Accountants

Item 9.01 Financial Statements and Exhibits (d) Exhibits Exhibit Number Description 99.1 News release issued by ONE Gas, Inc. dated September 29, 2026. 104 Cover Page Interactive Data File (embedded within the Inline XBRL document). 3 SIGNATURE Pursuant to the requirements of the Exchange Act, the registrant has duly caused this report to be signed on its behalf by the undersigned, hereunto duly authorized. ONE Gas, Inc. Date: September 29, 2026 By: /s/ Christopher P. Sighinolfi Christopher P. Sighinolfi Senior Vice President and Chief Financial Officer