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