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Director Deferred Compensation Plan (the \"Plan\"). These RSUs were inadvertently reported in Table I on the reporting person's Form 4 filed May 8, 2023."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F4","text":"Once released, the RSUs corresponding to these dividend equivalent rights (\"DERs\") will become payable according to the election of payment designation that was filed by the reporting person subject to the Plan. 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Such payment will be either lump sum or in annual installments commencing on the May 31st next following the reporting person's separation from service (as defined under the Plan) or, if later, and elected by the reporting person at the time he/she first elects to defer any payment under the Plan, May 31st of the year specified by the reporting person."}],"balance_after":9918,"derivative":{"underlying":"Common Stock","underlying_shares":3513},"source":{"system":"sec-edgar","filing":"0000950170-25-037432","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1245155/000095017025037432/ownership.xml","form_type":"4/A","original_submission_date":"2023-05-08"}},{"id":1211885,"issuer":{"id":5058,"kind":"organization","name":"Koppers Holdings Inc.","symbol":"KOP"},"owners":[{"id":37194,"kind":"person","name":"WILKERSON SONJA MICHELLE","position":1,"cik":"0001245155","reported_name":"WILKERSON SONJA MICHELLE","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Common Stock","published_at":"2025-03-11T22:39:35.000Z","date":"2025-03-07","kind":"disposition_to_issuer","planned":false,"acquired":false,"shares":3533,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"As disclosed in this Form 4 amendment, the reporting person inadvertently reported 3,513 RSUs and 20 DERs in Table I in the reporting person's previously-filed Forms 4. 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Such payment will be either lump sum or in annual installments commencing on the May 31st next following the reporting person's separation from service (as defined under the Plan) or, if later, and elected by the reporting person at the time he/she first elects to defer any payment under the Plan, May 31st of the year specified by the reporting person."}],"balance_after":6405,"derivative":{"underlying":"Common Stock","underlying_shares":2079},"source":{"system":"sec-edgar","filing":"0000950170-24-053683","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1245155/000095017024053683/ownership.xml","form_type":"4"}},{"id":1526169,"issuer":{"id":5058,"kind":"organization","name":"Koppers Holdings Inc.","symbol":"KOP"},"owners":[{"id":37194,"kind":"person","name":"WILKERSON SONJA MICHELLE","position":1,"cik":"0001245155","reported_name":"WILKERSON SONJA MICHELLE","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Dividend Equivalent Rights","published_at":"2024-05-06T21:10:11.000Z","date":"2024-05-02","kind":"exercise","planned":false,"acquired":false,"shares":20,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"These DERs were released in connection with the vesting of time-based restricted stock units granted on May 4, 2023. 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Each DER is the economic equivalent of one share of Koppers Holdings Inc. common stock."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Once released, the RSUs corresponding to these DERs will become payable according to the election of payment designation that was filed by the reporting person subject to the Koppers Holdings Inc. Director Deferred Compensation Plan (the \"Plan\"). 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