The amount of any penalty or assessment which has become final, or for which a judgment has been entered under §42.42 or §42.43 of this part, or any amount agreed upon in a compromise or settlement under §42.46 of this part, 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.