29 CFR § 97.52 - Collection of amounts due.
(a) Any funds paid to a grantee in excess of the amount to which the grantee is finally determined to be entitled under the terms of the award constitute a debt to the Federal Government. If not paid within a reasonable period after demand, the Federal agency may reduce the debt by:
(1) Making an adminstrative offset against other requests for reimbursements,
(2) Withholding advance payments otherwise due to the grantee, or
(3) Other action permitted by law.
(b) Except where otherwise provided by statutes or regulations, the Federal agency will charge interest on an overdue debt in accordance with the Federal Claims Collection Standards (4 CFR Ch. II). The date from which interest is computed is not extended by litigation or the filing of any form of appeal.