The agency must pay subsistence expenses (either a per diem allowance or actual expense) unless:

1. (a) The travel is to a training event under the Government Employees Training Act (5 U.S.C. 4101-4121), and the employee agrees not to be paid subsistence expenses; or
2. (b) The travel is for a pre-employment interview, and the interviewing agency does not authorize subsistence expense payment.