ONE Gas Inc 2025年度报告

X ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934For the fiscal year ended December 31, 2025 OR __TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934For the transition period from_______________to_______________ Commission file number001-36108 A. Full title of the plan and the address of the plan, if different from that of the issuer named below: ONE Gas, Inc. 401(k) Plan B. Name of issuer of the securities held pursuant to the plan and the address of its principal executive office: ONE Gas, Inc.15 East Fifth StreetTulsa, Oklahoma 74103 ONE Gas, Inc. 401(k) Plan TABLE OF CONTENTS The following financial statements prepared in accordance with the financial reporting requirements of the Employee RetirementIncome Security Act of 1974, as amended (“ERISA”), and exhibits are filed for the ONE Gas, Inc. 401(k) Plan: Financial Statements and Schedules Page Report of Independent Registered Public Accounting Firm3Financial Statements:Statements of Net Assets Available for Benefits - December31, 2025 and 20244Statement of Changes in Net Assets Available for Benefits - Year Ended December31, 20255Notes to Financial Statements6Schedules:Schedule H, Line 4a - Schedule of Delinquent Participant Contributions14Schedule H, Line 4i - Schedule of Assets (Held at End of Year)15Signature16Exhibit Index23 - Consent of Independent Registered Public Accounting Firm17 All other schedules required by the Department of Labor’s Rules and Regulations for Reporting and Disclosure under ERISA areomitted as they are inapplicable or not required. Report of Independent Registered Public Accounting Firm ONE Gas, Inc. Audit CommitteeONE Gas, Inc. Benefits Committee and Plan ParticipantsONE Gas, Inc.Tulsa, Oklahoma Opinion on the Financial StatementsWe have audited the accompanying statements of net assets available for benefits of the ONE Gas, Inc. 401(k) Plan (the Plan) as of December31, 2025 and 2024, the related statement of changes in net assets available for benefits for the year ended December31,2025, and the related notes (collectively referred to as the “financial statements”). In our opinion, the financial statements referred toabove present fairly, in all material respects, the net assets available for benefits of the Plan as of December31, 2025 and 2024 and thechanges in net assets available for benefits for the year ended December31, 2025, in conformity with accounting principles generallyaccepted in the United States of America. Basis of OpinionThese financial statements are the responsibility of the Plan’s management. Our responsibility is to express an opinion on these financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and arerequired to be independent with respect to the Plan in accordance with the U.S. federal securities laws and the applicable rules andregulations of the Securities and Exchange Commission and the PCAOB. We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the auditsto obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud.The Plan is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part ofour audits, we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressingan opinion on the effectiveness of the Plan’s internal control over financial reporting. Accordingly, we express no such opinion. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due toerror or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidenceregarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles usedand significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believethat our audits provide a reasonable basis for our opinion. Report on Supplemental InformationThe supplemental information in the accompanying Schedule H, Line 4i – Schedule of Assets (Held at End of Year) as of December31, 2025 has been subjected to audit procedures performed in conjunction with the audit of the Plan’s financial statements.The supplemental schedule is the responsibility of the Plan’s management. Our audit procedures included determining whether thesupplemental schedule reconciles to the financial statements or the underlying accounting and other records, as applicable, andperforming procedures to test the completeness and accuracy of the information presented in the supplemental schedule. In formingour opinion on the supplement