39 U.S.C. § 3206: Reimbursement for penalty mail service

Except as provided in subsection (b) of this section, executive departments and agencies, independent establishments of the Government of the United States, and Government corporations concerned, shall transfer to the Postal Service as postal revenue out of any appropriations or funds available to them, as a necessary expense of the appropriations or funds and of the activities concerned, the equivalent amount of postage due, as determined by the Postal Service, for matter sent in the mails by or to them as penalty mail under authority of section 3202 of this title . The Department of Agriculture shall transfer to the Postal Service as postal revenues out of any appropriations made to it for that purpose the equivalent amount of postage, as determined by the Postal Service, for penalty mailings under clauses (1)(F) and (4) of section 3202(a) of this title . The Department of State shall transfer to the Postal Service as postal revenues out of any appropriations made to it for that purpose the equivalent amount of postage, as determined by the Postal Service, for penalty mailings under clause (1)(C) and (D) of section 3202(a) of this title .