Results of Operations and Financial Condition. On August 6, 2026, Koppers Holdings Inc. (the “Company” or “we”) issued a press release announcing second quarter of 2026 results. A copy of the press release is included in this Current Report on Form 8-K as Exhibit 99.1 and is furnished herewith.

Chief Financial Officer and Treasurer — Eric D. Brenner: Eric D. Brenner was hired as the Chief Financial Officer and Treasurer from an external company.

Regulation FD Disclosure. The Company issued a press release on May 8, 2026 announcing the conditional plan to discontinue distillation and chemical manufacturing operations activities at its facility in Stickney, Illinois. A copy of the press release is included in this Current Report on Form 8-K as Exhibit 99.2 and is furnished herewith. The information in Items 2.02 and 7.01 above, including Exhibits 99.1 and 99.2 attached to this Current Report on Form 8-K, are being furnished under Items…

Results of Operations and Financial Condition. On May 8, 2026, Koppers Holdings Inc. (the “Company” or “we”) issued a press release announcing first quarter of 2026 results. A copy of the press release is included in this Current Report on Form 8-K as Exhibit 99.1 and is furnished herewith.

The filing pertains to the approval of an amendment to the Employee Stock Purchase Plan, which is a non-management event.

Costs Associated with Exit or Disposal Activities. On May 8, 2026, the Company announced that it has made a conditional decision to discontinue distillation and chemical manufacturing operations at its facility in Stickney, Illinois, subject to the satisfaction of any bargaining obligations that might exist with the union that represents certain employees at that facility. The conditional decision, which is pending negotiations and consultation with the union, was driven by challenging market…

Director — Laura J. Posadas: Ms. Laura J. Posadas was elected as a member of the Board and appointed to several committees.

Treasurer — Ms. Smith: Ms. Smith is leaving her role as Treasurer with a transition agreement.

Results of Operations and Financial Condition. On February 26, 2026 we issued a press release announcing fourth quarter and full year 2025 results. A copy of the press release is included in this Current Report on Form 8-K as Exhibit 99.1 and is furnished herewith.

CFO — Jimmi Sue Smith: The CFO is retiring but remaining as Treasurer and advisor, with an internal Chief Accounting Officer appointed as interim successor, indicating an orderly transition rather than a sudden loss of leadership.

Costs Associated with Exit or Disposal Activities. The Company estimates pre-tax restructuring charges, employee severance charges and related benefit costs for actions associated with the workforce reduction program to be in the range of $4 million to $5 million, which the Company anticipates will result in future cash expenditures of approximately $1 million. In accordance with paragraph (d) of Item 2.05, the Company will timely file additional amendment(s) to this Current Report on Form 8-…

Results of Operations and Financial Condition. On November 7, 2025 we issued a press release announcing third quarter of 2025 results. A copy of the press release is included in this Current Report on Form 8-K as Exhibit 99.1 and is furnished herewith.

Director — Laura Posadas: The filing discloses the addition of a new independent director to the board, which is a standard governance action and not a departure of an executive.

Results of Operations and Financial Condition. On August 8, 2025 we issued a press release announcing second quarter of 2025 results. A copy of the press release is included in this Current Report on Form 8-K as Exhibit 99.1 and is furnished herewith.

Entry into a Material Definitive Agreement. On June 17, 2025, Koppers Inc. (“Koppers” or the “Company”), a wholly-owned subsidiary of Koppers Holdings Inc. (“Holdings”), entered into Amendment No. 6 (“Amendment No. 6”) with Holdings, certain lenders and letter of credit issuers, and PNC Bank, National Association, as revolving administrative agent and swingline loan lender, which amends that certain Credit Agreement, dated June 17, 2022 (as amended by that certain Amendment No. 1, dated April…

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The description of the terms of Amendment No. 6 set forth above in

President — James A. Sullivan: James A. Sullivan was promoted from President and COO to President and Chief Transformation Officer, representing an internal advancement rather than a departure.

The filing discloses the shareholder approval of an amended long-term incentive plan, which is a compensatory arrangement rather than a change in management personnel.

Results of Operations and Financial Condition. On May 9, 2025 we issued a press release announcing first quarter of 2025 results. A copy of the press release is included in this Current Report on Form 8-K as Exhibit 99.1 and is furnished herewith.

Results of Operations and Financial Condition. On February 27, 2025 we issued a press release announcing fourth quarter and full year 2024 results. A copy of the press release is included in this Current Report on Form 8-K as Exhibit 99.1 and is furnished herewith.

Entry into a Material Definitive Agreement. On December 17, 2024 (the “Closing Date”), Koppers Inc. (“Koppers” or the “Company”), a wholly-owned subsidiary of Koppers Holdings Inc. (“Holdings”), entered into Amendment No. 5 (“Amendment No. 5”) to the Credit Agreement, dated June 17, 2022, with Holdings, certain lenders and letter of credit issuers, PNC Bank, National Association, as revolving administrative agent, collateral agent and swingline loan lender, and Wells Fargo Bank, National Asso…

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The description of the terms of Amendment No. 5 set forth above in

Chief Sustainability Officer — Leslie S. Hyde: The filing describes a planned retirement with an internal transition role, indicating an orderly succession rather than a sudden loss of a senior executive.

Costs Associated with Exit or Disposal Activities. On December 5, 2024, Koppers Inc. (the “Company”), a wholly owned subsidiary of Koppers Holdings Inc., decided to discontinue phthalic anhydride production at the Company’s facility in Stickney, Illinois. The decision, affecting approximately 25 employees, was driven by significant near-term capital spending requirements that could not be economically justified by end-market projections and will substantially reduce annual emissions of certai…

Results of Operations and Financial Condition. On November 8, 2024 we issued a press release announcing third quarter of 2024 results. A copy of the press release is included in this Current Report on Form 8-K as Exhibit 99.1 and is furnished herewith.