In the case of a taxable year to which section
26
(a)(2) applies, if the credit allowable under subsection (a) for any taxable year exceeds the limitation imposed by section
26
(a)(2) for such taxable year reduced by the sum of the credits allowable under this subpart (other than this section and sections
25D and
1400C), such excess shall be carried to the succeeding taxable year and added to the credit allowable under subsection (a) for such taxable year.