14 CFR §1264.143

The amount of any penalty or assessment which has become final, or for which a judgment has been entered under § 1264.141 or § 1264.142, or any amount agreed upon in a compromise or settlement under § 1264.145, may be collected by administrative offset under 31 U.S.C. 3716, except that an administrative offset may not be made under this subsection against a refund of an overpayment of Federal taxes, then or later owing by the United States to the defendant.