Any portion of an internal revenue tax (or any interest, assessable penalty, additional amount, or addition to tax) which has been erroneously refunded, and which is recoverable by a civil action pursuant to 26 U.S.C. 7405, shall bear interest at the underpayment rate referred to in § 70.93 of this part.

(26 U.S.C. 6602)

[T.D. ATF-301, 55 FR 47614, Nov. 14, 1990]