Termination of a Material Definitive Agreement. On August 14, 2026, the outstanding loans under the Existing Credit Agreement were paid in full (together with accrued interest and fees thereunder), the commitments to extend credit under the Existing Credit Agreement were terminated, and all guarantees and security interests in respect of the Existing Credit Agreement were released.

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

Entry into a Material Definitive Agreement. Credit Agreement On August 14, 2026 (the “Closing Date”), AdvanSix Inc. (the “Company”) completed a refinancing of its existing senior secured revolving credit facility under that certain Credit Agreement, dated as of October 27, 2021 (as amended by Amendment No. 1, dated June 27, 2023, Amendment No. 2, dated October 23, 2025, and as further amended, restated, amended and restated, supplemented or otherwise modified from time to time prior to the da…

Other Events. Dividend On August 7, 2026, the Company announced that its Board of Directors declared a cash dividend of $0.16 per share on the Company's common stock. The dividend will be paid on September 1, 2026 to stockholders of record as of the close of business on August 18, 2026. The Company's announcement of the dividend is included in the press release furnished herewith as Exhibit 99.1.

Results of Operations and Financial Condition. On August 7, 2026, AdvanSix Inc. (the "Company") issued a press release announcing its financial results for the quarter ended June 30, 2026. A copy of the press release is furnished herewith as Exhibit 99.1.

Other Events. Dividend On May 8, 2026, the Company announced that its Board of Directors declared a cash dividend of $0.16 per share on the Company's common stock. The dividend will be paid on June 2, 2026 to stockholders of record as of the close of business on May 19, 2026. The Company's announcement of the dividend is included in the press release furnished herewith as Exhibit 99.1.

Results of Operations and Financial Condition. On May 8, 2026, AdvanSix Inc. (the "Company") issued a press release announcing its financial results for the quarter ended March 31, 2026. A copy of the press release is furnished herewith as Exhibit 99.1.

Chief Financial Officer — Patrick C. Day: Patrick C. Day was hired as the new Chief Financial Officer from an external company.

Results of Operations and Financial Condition. On February 20, 2026, AdvanSix Inc. (the "Company") issued a press release announcing its financial results for the quarter and full year ended December 31, 2025. A copy of the press release is furnished herewith as Exhibit 99.1.

Other Events. Dividend On February 20, 2026, the Company announced that its Board of Directors declared a cash dividend of $0.16 per share on the Company's common stock. The dividend will be paid on March 23, 2026 to stockholders of record as of the close of business on March 9, 2026. The Company's announcement of the dividend is included in the press release furnished herewith as Exhibit 99.1.

Director — Jeffrey J. Bird: Appointment of Jeffrey J. Bird as a Director and to serve on the Audit Committee and Health, Safety and Environmental Committee.

Results of Operations and Financial Condition. On November 7, 2025, AdvanSix Inc. (the "Company") issued a press release announcing its financial results for the quarter ended September 30, 2025. A copy of the press release is furnished herewith as Exhibit 99.1.

Other Events. Dividend On November 7, 2025, the Company announced that its Board of Directors declared a cash dividend of $0.16 per share on the Company's common stock. The dividend will be paid on December 2, 2025 to stockholders of record as of the close of business on November 18, 2025. The Company's announcement of the dividend is included in the press release furnished herewith as Exhibit 99.1.

Entry into a Material Definitive Agreement. Amendment No. 2 to Credit Agreement On October 23, 2025, AdvanSix Inc. (the “Company”) entered into Amendment No. 2 (the “Amendment”) to the Credit Agreement, dated as of October 27, 2021 (as amended by Amendment No. 1, dated June 27, 2023, the “Existing Credit Agreement” and as further amended by the Amendment, the “Amended Credit Agreement”), among the Company, the guarantors, the lenders party thereto and Truist Bank, as administrative agent. Any…

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

Director — Dana O'Brien and Daryl Roberts: The appointment of two new directors with extensive experience in public company governance, operations, and regulatory compliance.

Other Events. Dividend On August 1, 2025, the Company announced that its Board of Directors declared a cash dividend of $0.16 per share on the Company's common stock. The dividend will be paid on August 26, 2025 to stockholders of record as of the close of business on August 12, 2025. The Company's announcement of the dividend is included in the press release furnished herewith as Exhibit 99.1.

Results of Operations and Financial Condition. On August 1, 2025, AdvanSix Inc. (the "Company") issued a press release announcing its financial results for the quarter ended June 30, 2025. A copy of the press release is furnished herewith as Exhibit 99.1.

Chief Financial Officer — Siddharth Manjeshwar: The CFO's employment was terminated and an interim replacement was appointed.

The filing pertains to the approval of an amended stock incentive plan, not a management change.

Results of Operations and Financial Condition. On May 2, 2025, AdvanSix Inc. (the "Company") issued a press release announcing its financial results for the quarter ended March 31, 2025. A copy of the press release is furnished herewith as Exhibit 99.1.

Other Events. Dividend On May 2, 2025, the Company announced that its Board of Directors declared a cash dividend of $0.16 per share on the Company's common stock. The dividend will be paid on May 27, 2025 to stockholders of record as of the close of business on May 13, 2025. The Company's announcement of the dividend is included in the press release furnished herewith as Exhibit 99.1.

Director — Farha Aslam and Darrell K. Hughes: Both directors are resigning due to other commitments.

Vice President, Financial Planning and Analysis — Christopher Gramm: Christopher Gramm has been promoted to Vice President, Financial Planning and Analysis.

Results of Operations and Financial Condition. On February 21, 2025, AdvanSix Inc. (the "Company") issued a press release announcing its financial results for the quarter and full year ended December 31, 2024. A copy of the press release is furnished herewith as Exhibit 99.1.