year an amount equal to the sum of the credits determined under subsection (b) with respect to such dates. (b) Amount of credit (1) In general The amount of the credit determined under this subsection with respect to any interest payment date for a clean energy bond is the applicable percentage (as determined under paragraph (2)) of the amount of interest payable by the issuer with respect to such date. (2) Applicable percentage (A) In general (i) Maximum percentage Except as provided in clause (ii), the applicable percentage is 70 percent. (ii) Reduction of credit based on greenhouse gas emission rate The applicable percentage shall be reduced (but not below zero) by an amount which bears the same ratio to the percentage in effect under clause (i) as— (I) in the case of a qualified facility described in subsection (e)(3) of section 45S, the greenhouse gas emissions rate for the facility bears to 325 grams of CO 2 e per KWh (as such terms are defined in subsections (b)(1) and (e)(1) of such section), or (II) in the case of a qualified facility described in subsection (e)(4) of section 45T, the average emissions rate for all transportation fuel produced by such facility bears to 75 kilograms of CO 2 e per mmBTU (as such terms are defined in subsections (b) and (e) of such section). (B) Rounding If any applicable percentage determined under subparagraph (A) is not a whole percentage point, such percentage shall be rounded to the nearest whole percentage point. (C) Safe harbor rules Rules similar to the rules of sections 45S(b)(3) and 45T(b) shall apply for purposes of this section. (c) Limitation based on amount of tax (1) In general The credit allowed under subsection (a) for any taxable year shall not exceed the excess of— (A) the sum of the regular tax liability (as defined in section 26(b)) plus the tax imposed by section 55, over (B) the sum of the credits allowable under this part (other than subpart C and this subpart). (2) Carryover of unused credit If the credit allowable under subsection (a) exceeds the