41 CFR § 304-6.3
What happens if an employee accepts payment from a non-Federal source that is in violation of this part?
June 9, 2020
If an employee accepts payment from a non-Federal source in violation of this part—
(a) You may require the employee, in addition to any penalty provided by law and applicable regulations, to pay the general fund of the Treasury, an amount equal to the payment so accepted; and
(b) The employee shall not be entitled to any reimbursement from the Government for such expenses.