28 U.S.C. § 1924 - U.S. Code - Unannotated Title 28. Judiciary and Judicial Procedure § 1924. Verification of bill of costs

Before any bill of costs is taxed, the party claiming any item of cost or disbursement shall attach thereto an affidavit, made by himself or by his duly authorized attorney or agent having knowledge of the facts, that such item is correct and has been necessarily incurred in the case and that the services for which fees have been charged were actually and necessarily performed.