Koppers Holdings Inc

The management of Koppers Holdings Inc. is responsible for establishing and maintaining adequate internal control over financial reporting. Internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external reporting purposes in accordance with accounting principles generally accepted in the United States of America.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Management has assessed the effectiveness of Koppers Holdings Inc.’s internal control over financial reporting as of December 31, 2024. In making this assessment, management has utilized the criteria set forth by the Committee of Sponsoring Organizations of the Treadway Commission (COSO) in Internal Control – Integrated Framework (2013 Framework). Management concluded that based on its assessment, Koppers Holdings Inc.’s internal control over financial reporting was effective as of December 31, 2024.

The effectiveness of Koppers Holdings Inc.’s internal control over financial reporting as of December 31, 2024, has been audited by KPMG LLP, the independent registered public accounting firm that also audited the consolidated financial statements included in this annual report, as stated in their attestation report which appears on the following page.

February 27, 2025

/S/ LEROY M. BALL

Leroy M. Ball

Chief Executive Officer

/S/ JIMMI SUE SMITH

Jimmi Sue Smith

Chief Financial Officer