41 CFR § 301-52.19
Will I receive a late payment fee if my agency fails to reimburse me within 30 calendar days after I submit a proper travel claim?
June 9, 2020
Yes, your agency must pay you a late payment fee, in addition to the amount due you, for any proper travel claim not reimbursed within 30 calendar days of your submission of it to the approving official.
[FTR Amdt. 90, 65 FR 3056, Jan. 19, 2000]