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 section 7405, shall bear interest at the annual rate referred to in the regulations under section 6621 from the date of the payment of the refund.

[T.D. 7384, 40 FR 49324, Oct. 22, 1975]