19 U.S.C. § 2078 : US Code - Section 2078: Certification of reason for advance

Search 19 U.S.C. § 2078 : US Code - Section 2078: Certification of reason for advance

A certificate by the Commissioner of Customs stating the amount
of an expenditure made from funds advanced and certifying that the
confidential nature of the transaction involved renders it
inadvisable to specify the details thereof or impracticable to
furnish the payee's receipt shall be a sufficient voucher for the
sum expressed to have been expended.