301-73.301—How do we obtain travel payment system services?
A system to facilitate the payment of official travel and transportation expenses which includes, but is not limited to:
(b)
Establishment of centrally billed accounts for the purchase of travel and transportation services;
Code of Federal Regulations
You may participate in GSA's or another Federal agency's travel payment system services program or you may contract directly with a travel payment system service if your agency has contracting authority and you are not a mandatory user of GSA's charge card program.