27 C.F.R. § 70.121
(b) An amount paid as tax shall not be considered not to constitute an overpayment solely by reason of the fact that there was no tax liability in respect of which such amount was paid.
(26 U.S.C. 6401)
[T.D. ATF-251, 52 FR 19314, May 22, 1987. Redesignated by T.D. ATF-301, 55 FR 47606, Nov. 14, 1990]