Koppers Holdings Inc. 10-Q

ITEM 5. OTHER INFORMATION During the three months ended March 31, 2026, none of our directors or executive officers adopted , modified or terminated any Rule 10b5-1 trading arrangement or any non-Rule 10b5-1 trading arrangement (as such terms are defined in Item 408 of Regulation S-K). ITEM 6. EXHIBITS 10.1* Transition Agreement and General Release with Jimmi Sue Smith. 10.2 First Amendment to the Koppers Holdings Inc. Amended and Restated Employee Stock Purchase Plan (Incorporated herein by reference to Exhibit 99.2 to our Registration Statement on Form S-8 filed on May 8, 2026 (File No. 333-295681)). 10.3* Form of Restricted Stock Unit Issuance Agreement Non-Employee Director - Time Vesting . 31.1* Certification of Chief Executive Officer Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. 31.2* Certification of Chief Financial Officer Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. 32.1* Certification of Chief Executive Officer and Chief Financial Officer pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. 101.INS* Inline XBRL Instance Document – the instance document does not appear in the Interactive Data File because its XBRL tags are embedded with the Inline XBRL document. 101.SCH* Inline XBRL Taxonomy Extension Schema With Embedded Linkbase Documents 104 Cover Page Interactive Data File (formatted as Inline XBRL and contained in Exhibit 101) * Filed herewith. 27 SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized. K OPPERS H OLDINGS I NC. (R EGISTRANT ) Date: May 8, 2026 By: /s/ B RADLEY A . P EARCE Bradley A. Pearce Interim Chief Financial Officer and Treasurer and Chief Accounting Officer (Principal Financial Officer and Duly Authorized Officer) 28