41 C.F.R. § 301-71.204

When disallowing a travel claim, the agency must:

(a) Pay the undisputed portion of the travel claim;

(b) Provide the employee with a detailed explanation for the claim's disallowance; and

(c) Inform the employee:

(1) How to appeal the disallowance;

(2) About the agency's appeal process; and

(3) Of the schedule for deciding the appeal.