Entry into a Material Definitive Agreement ​ On August 11, 2026, Hallador Energy Company (the “Company”) entered into a Third Amendment to Credit Agreement (the “Third Amendment”), by and among the Company, Texas Capital Bank, as administrative agent (the “Administrative Agent”), and the lenders party thereto (the “Lenders”), which amends the Credit Agreement, dated as of March 5, 2026, among the Company, the Administrative Agent and the Lenders party thereto (as amended by the First Amendmen…

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

Results of Operations and Financial Condition ​ On August 10, 2026, Hallador Energy Company issued a press release announcing its second q uarter 2026 financial and operating results. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated by reference herein. ​ The information included in this Current Report on Form 8-K, including Exhibit 99.1 hereto, that is furnished pursuant to this

Entry into a Material Definitive Agreement ​ On June 25, 2026, Hallador Energy Company (the "Company") entered into a Second Amendment (the "Amendment") to its Credit Agreement, dated as of March 5, 2026 (as amended, the "Credit Agreement"), by and among the Company, Texas Capital Bank, as administrative agent (the "Administrative Agent"), and the lenders party thereto (the "Lenders"), which provides for, among other things, the revision of certain financial covenants under the credit facilit…

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

Chief Legal Officer — Matthew Bradford White: The company appointed a new Chief Legal Officer from an external hire.

Entry into a Material Definitive Agreement. On May 30, 2026, Hallador Energy Company (the “Company”) entered into an Asset Purchase Agreement (the “APA”) with Energy World Corporation Ltd., incorporated in Australia (“Seller”), to acquire approximately 460 MW of Siemens gas turbines, generators, a steam turbine, and ancillary equipment (the “Equipment”) for an aggregate purchase price of $350 million. The foregoing description of the APA does not purport to be complete and is qualified in its…

Chair of the Risk Committee — Daniel Hudson: Daniel Hudson was appointed as Chair of the newly formed Risk Committee with an additional retainer.

Results of Operations and Financial Condition ​ On May 6, 2026, Hallador Energy Company issued a press release announcing its first q uarter 2026 financial and operating results. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated by reference herein. ​ The information included in this Current Report on Form 8-K, including Exhibit 99.1 hereto, that is furnished pursuant to this

The filing details a new executive compensation plan and salary increases, which are routine updates to the company's management compensation structure.

Results of Operations and Financial Condition ​ On March 12, 2026, Hallador Energy Company issued a press release announcing its fourth q uarter and full year 2025 financial and operating results. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated by reference herein. ​ The information included in this Current Report on Form 8-K, including Exhibit 99.1 hereto, that is furnished pursuant to this

Entry into a Material Definitive Agreement. ​ On March 5, 2026, Hallador Energy Company (the “Company”) entered into a Credit Agreement (the “Credit Agreement”), among the Company, Texas Capital Bank, as administrative agent (the “Agent”), swingline lender and letter of credit issuer, Old National Bank, as joint lead arranger and letter of credit issuer, First Financial Bank, N.A., as lender, each other lender from time to time party thereto, and each other letter of credit issuer from time t…

Termination of a Material Definitive Agreement. ​ In connection with the Company’s entry into the Credit Agreement, on March 4, 2026, the Company delivered written notice to PNC Bank, National Association to terminate the Company’s Existing Credit Agreement, effective as of March 5, 2026. The Company is not subject to any termination penalties related to the termination of the Existing Credit Agreement. ​ A copy of the Existing Credit Agreement was filed as Exhibit 10.1 to the Form 10-Q filed…

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

Chief Operating Officer — Heath Lovell: Heath Lovell was promoted to Chief Operating Officer.

Other Events. On January 13, 2026, the Company entered into an underwriting agreement (the “Underwriting Agreement”) with TCBI Securities, Inc., doing business as Texas Capital Securities, as representative of the several underwriters named therein (the “Underwriters”), relating to the issuance and sale of an aggregate of 2,777,778 shares (the “Firm Shares”) of the Company’s common stock, par value $0.01 per share (“Common Stock”), to the Underwriters (the “Offering”). Pursuant to the Underwr…

Termination of a Material Definitive Agreement. As previously disclosed, on December 18, 2023, Hallador Energy Company (the “Company”) entered into an At Market Issuance Sales Agreement (the “Sales Agreement”) with B. Riley Securities, Inc. (the “Agent”), pursuant to which the Company may issue and sell, from time to time, shares of its common stock, par value $0.01 per share (the “Common Stock”) (the “ATM Program”). Pursuant to the registration statement on Form S-3 (File No. 333-273327) fil…

Director — David Hardie: Mr. Hardie resigned from the Board, but his departure was not due to any disagreement with the Company.

Chief Accounting Officer and Senior Vice President — Eric Van Deman: The company appointed a new Chief Accounting Officer and Senior Vice President.

Results of Operations and Financial Condition ​ On November 10, 2025, Hallador Energy Company issued a press release announcing its third quarter 2025 financial and operating results. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated by reference herein. ​ The information included in this Current Report on Form 8-K, including Exhibit 99.1 hereto, that is furnished pursuant to this

Results of Operations and Financial Condition ​ On August 11, 2025, Hallador Energy Company issued a press release announcing its second quarter 2025 financial and operating results. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated by reference herein. ​ The information included in this Current Report on Form 8-K, including Exhibit 99.1 hereto, that is furnished pursuant to this

The filing pertains to the approval of a stock unit plan, not a management change.

Results of Operations and Financial Condition ​ On May 12, 2025, Hallador Energy Company issued a press release announcing its first quarter 2025 financial and operating results. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated by reference herein. ​ The information included in this Current Report on Form 8-K, including Exhibit 99.1 hereto, that is furnished pursuant to this

Results of Operations and Financial Condition ​ On March 17, 2025, Hallador Energy Company issued a press release announcing its fourth quarter and full year 2024 financial and operating results. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated by reference herein. ​ The information included in this Current Report on Form 8-K, including Exhibit 99.1 hereto, that is furnished pursuant to this

Results of Operations and Financial Condition ​ On November 12, 2024, Hallador Energy Company issued a press release announcing its third quarter 2024 financial results. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated by reference herein. ​ The information included in this Current Report on Form 8-K, including Exhibit 99.1 hereto, that is furnished pursuant to this