41 CFR § 301-71.213
Is the additional fee, which is the equivalent to any late payment charge that the card contractor would have been able to charge had the employee not paid the bill, considered income?
June 9, 2020
Yes, you must report this late payment fee as additional wages on Form W-2.
[FTR Amdt. 90, 65 FR 3058, Jan. 19, 2000]