Entry into a Material Definitive Agreement Underwriting Agreement On August 11, 2026, ONE Gas, Inc. (“ONE Gas”) entered into an underwriting agreement (the “Underwriting Agreement”) with BofA Securities, Inc., RBC Capital Markets, LLC and Truist Securities, Inc., as representatives of the underwriters named therein (the “Underwriters”), with respect to the issuance and sale by ONE Gas of $375,000,000 aggregate principal amount of its 5.45% Senior Notes due 2036 (the “Notes”). The Underwriting…

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant The information included in

Results of Operations and Financial Condition On August 4, 2026, we announced our results of operations for the quarter ended June 30, 2026. The news release is furnished as Exhibit 99.1 and incorporated by reference herein.

Other Events On August 4, 2026, our board of directors declared a cash dividend of 68 cents per share of common stock, payable August 31, 2026, to shareholders of record at the close of business on August 17, 2026.

Regulation FD Disclosure On August 4, 2026, we announced our results of operations for the quarter ended June 30, 2026, raised 2026 financial guidance, and declared a cash dividend of 68 cents per share of common stock. The news release is furnished as Exhibit 99.1 and is incorporated by reference herein.

Director — Nickolas Stavropoulos: Nickolas Stavropoulos was appointed to the Board of Directors.

Results of Operations and Financial Condition On May 4, 2026, we announced our results of operations for the quarter ended March 31, 2026. The news release is furnished as Exhibit 99.1 and incorporated by reference herein.

Other Events On May 4, 2026, our board of directors declared a cash dividend of 68 cents per share of common stock, payable June 2, 2026, to shareholders of record at the close of business on May 18, 2026.

Regulation FD Disclosure On May 4, 2026, we announced our results of operations for the quarter ended March 31, 2026, affirmed our 2026 financial guidance and announced that our board of directors declared a cash dividend of 68 cents per share of common stock. The news release is furnished as Exhibit 99.1 and is incorporated by reference herein.

Entry into a Material Definitive Agreement On February 23, 2026, ONE Gas, Inc. (the “ Company ”) entered into an equity distribution agreement (the “ Equity Distribution Agreement ”) with BofA Securities, Inc. (“ BofA Securities ”), BTIG, LLC (“ BTIG ”), Huntington Securities, Inc. (“ HSI ”), J.P. Morgan Securities LLC (“ J.P. Morgan ”), Mizuho Securities USA LLC (“ Mizuho ”), RBC Capital Markets, LLC (“ RBC ”) and Truist Securities, Inc. (“ TSI ”), each acting as sales agent for the Company…

President and Chief Operating Officer — Curtis L. Dinan: Curtis L. Dinan was promoted to President and Chief Operating Officer.

Results of Operations and Financial Condition On February 18, 2026, we announced our results of operations for the fourth quarter and year ended December 31, 2025. The news release is furnished as Exhibit 99.1 and incorporated by reference herein.

Regulation FD Disclosure On January 20, 2026, we announced that our board of directors declared a cash dividend of 68 cents per share of common stock. A copy of the news release is attached as Exhibit 99.1 and is incorporated herein by reference.

Other Events On January 20, 2026, our board of directors declared a cash dividend of 68 cents per share of common stock, payable March 6, 2026, to shareholders of record at close of business February 20, 2026.

Entry into a Material Definitive Agreement. The information related to our $1.50 billion unsecured commercial paper program described under

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. On December 17, 2025, we increased the size of our commercial paper program to permit the issuance of commercial paper notes in an aggregate principal amount not to exceed $1.50 billion at any time outstanding. Prior to this increase, our commercial paper program permitted us to issue commercial paper notes in an aggregate principal amount not to exceed $1.35 billion at any time…

Director — John W. Gibson: The filing discloses the planned retirement of a long-serving board chair with a named internal successor, representing an orderly succession rather than a sudden loss of executive leadership.

Results of Operations and Financial Condition On November 3, 2025, we announced our results of operations for the quarter ended September 30, 2025. The news release is furnished as Exhibit 99.1 and incorporated by reference herein.

Regulation FD Disclosure On November 3, 2025, we announced our results of operations for the quarter ended September 30, 2025, narrowed 2025 financial guidance, and declared a cash dividend of 67 cents per share of common stock. The news release is furnished as Exhibit 99.1 and is incorporated by reference herein.

Other Events On November 3, 2025, our board of directors declared a cash dividend of 67 cents per share of common stock, payable December 1, 2025, to shareholders of record at the close of business on November 14, 2025.

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The information included under

Entry Into a Material Definitive Agreement. On October 30, 2025, ONE Gas, Inc., an Oklahoma corporation (the “ Company ”), entered into a third amended and restated credit agreement (the “ Credit Agreement ”) with Bank of America, N.A., as administrative agent, swing line lender, a letter of credit issuer and a lender and the other lenders and letter of credit issuers parties thereto. The Credit Agreement amends and restates the current Second Amended and Restated Credit Agreement, dated as o…

Entry Into a Material Definitive Agreement. On August 11, 2025, ONE Gas, Inc. (the “ Company ”) entered into a credit agreement (the “ Credit Agreement ”) with Bank of America, N.A., as administrative agent, and the lenders party thereto. The Credit Agreement provides for a $250 million unsecured term loan facility. Proceeds of the loans under the Credit Agreement will be available for working capital, capital expenditures, acquisitions, mergers, and other general corporate purposes. The Cred…

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The information included under

Results of Operations and Financial Condition On August 5, 2025, we announced our results of operations for the quarter ended June 30, 2025. The news release is furnished as Exhibit 99.1 and incorporated by reference herein.