41 CFR § 301-71.206
What must we do if we disallow a travel claim?
June 9, 2020
You must:
(a) Pay the employee the amount of the travel claim which is not in dispute;
(b) Notify the employee that the claim was disallowed with a detailed explanation of why; and
(c) Tell the employee how to appeal the disallowance if he/she desires an appeal, and your process and schedule for deciding the appeal.