41 CFR 102-118.40 – How does my agency order transportation and transportation services?
Your agency orders:
(a) Transportation of freight and household goods and related transportation services (e.g., packaging, storage) with a Government contractor-issued charge card, purchase order (or electronic equivalent), or a Government bill of lading for international shipments (including domestic overseas shipments). In extremely limited cases, cash can be used where government payment mechanisms are not available or acceptable.
(b) Transportation of people through the purchase of transportation tickets with a Government issued charge card (or centrally billed travel account citation), Government issued individual travel charge card, personal charge card, cash (in accordance with Department of the Treasury regulations), or in limited prescribed situations, a Government Transportation Request (GTR). See the “U.S. Government Passenger Transportation Handbook,” available at https://www.gsa.gov/transaudits.