41 CFR § 301-51.7
For what purposes may I use the Government contractor-issued travel charge card while on official travel?
June 9, 2020
You are required to use the Government contractor-issued travel charge card for expenses directly related to your official travel.
[FTR Amdt. 2010-02, 75 FR 24436, May 5, 2010. Redesignated by FTR Amdt. 2016-01, 81 FR 63138, Sept. 14, 2016]