41 CFR § 301-50.5
What is my liability if I do not use my agency's TMS or the E-Gov Travel Service, and an exception has not been approved?
June 9, 2020
If you do not have an approved exception under §301-50.4 or §301-73.104 of this chapter, you are responsible for any additional costs resulting from the failure to use the TMS or E-Gov Travel Service, including service fees, cancellation penalties, or other additional costs (e.g., higher airfares, rental car charges, or hotel rates). In addition, your agency may take appropriate disciplinary action.
[FTR Amdt. 2003-07, 68 FR 71029, Dec. 22, 2003, as amended by FTR Amdt. 2007-05, 72 FR 61538, Oct. 31, 2007]