Each agency that receives a bill from a carrier or freight forwarder for transporting an individual or property for the United States Government shall verify its correctness (to include transportation rates, freight classifications, or proper combinations thereof), using prepayment audit, prior to payment in accordance with the requirements of this section and regulations prescribed by the Administrator of General Services.

The Administrator of General Services may exempt bills, a particular mode or modes of transportation, or an agency or subagency from a prepayment audit and verification and in lieu thereof require a postpayment audit, based on cost effectiveness, public interest, or other factors the Administrator considers appropriate.

Expenses for prepayment audits shall be funded by the agency’s appropriations used for the transportation services.

The audit authority provided to agencies by this section is subject to oversight by the Administrator.