(1) 1-year carryback and 20-year carryforward If the sum of the business credit carryforwards to the taxable year plus the amount of the current year business credit for the taxable year exceeds the amount of the limitation imposed by subsection (c) of section 38 for such taxable year (hereinafter in this section referred to as the unused credit year), such excess (to the extent attributable to the amount of the current year business credit) shall be
(A) a business credit carryback to the taxable year preceding the unused credit year, and
(B) a business credit carryforward to each of the 20 taxable years following the unused credit year,
and, subject to the limitations imposed by subsections (b) and (c), shall be taken into account under the provisions of section 38 (a) in the manner provided in section 38 (a).
(2) Amount carried to each year
(A) Entire amount carried to first year
The entire amount of the unused credit for an unused credit year shall be carried to the earliest of the 21 taxable years to which (by reason of paragraph (1)) such credit may be carried.
(B) Amount carried to other 20 years The amount of the unused credit for the unused credit year shall be carried to each of the other 20 taxable years to the extent that such unused credit may not be taken into account under section
38 (a) for a prior taxable year because of the limitations of subsections (b) and (c).
(3) 5-year carryback for marginal oil and gas well production credit Notwithstanding subsection (d), in the case of the marginal oil and gas well production credit
(A) this section shall be applied separately from the business credit (other than the marginal oil and gas well production credit),
(B) paragraph (1) shall be applied by substituting each of the 5 taxable years for the taxable year in subparagraph (A) thereof, and
(C) paragraph (2) shall be applied
(i) by substituting 25 taxable years for 21 taxable years in subparagraph (A) thereof, and
(ii) by substituting 24 taxable years for 20 taxable years in subparagraph (B) thereof.