26 U.S.C. § 34

1. (a)There shall be allowed as a credit against the tax imposed by this subtitle for the taxable year an amount equal to the sum of the amounts payable to the taxpayer—
   1. (1)under section 6420 (determined without regard to section 6420(g)),
   2. (2)under section 6421 (determined without regard to section 6421(i)), and
   3. (3)under section 6427 (determined without regard to section 6427(k)).
2. (b)Credit shall not be allowed under subsection (a) for any amount payable under section 6421 or 6427, if a claim for such amount is timely filed and, under section 6421(i) or 6427(k), is payable under such section.