such paragraph as— (i) the amount (not less than zero) equal to the average gross receipts of the taxpayer over the 3 preceding taxable years minus $5,000,000, bears to (ii) $5,000,000. (B) Inflation adjustment In the case of any taxable year after 2020, each of the dollar amounts under subparagraph (A) shall be increased by an amount equal to— (i) such dollar amount, multiplied by (ii) the cost-of-living adjustment determined under section 1(f)(3) for the calendar year in which the taxable year begins, determined by substituting calendar year 2019 for calendar year 2016 in subparagraph (A)(ii) thereof. (C) Rounding If any reduction determined under subparagraph (A) is not a multiple of $50, or any increase under subparagraph (B) is not a multiple of $50, such amount shall be rounded to the nearest multiple of $50. (c) Qualified disaster mitigation expenditure For purposes of this section, the term qualified disaster mitigation expenditure has the same meaning given such term under paragraph (1) of section 25E(c), except that place of business shall be substituted for qualified dwelling unit each place it appears in such paragraph. (d) Special rules Rules similar to the rules of subsections (d) through (g) of section 25E shall apply for purposes of this section. . (b) Conforming amendments (1) Section 38(b) of such Code is amended by striking plus at the end of paragraph (31), by striking the period at the end of paragraph (32) and inserting , plus , and by adding at the end the following new paragraph: (33) the disaster mitigation credit determined under section 45T(a). . (2) The table of sections for subpart D of part IV of subchapter A of chapter 1 of such Code is amended by inserting after the item relating to section 45S the following new item: Sec. 45T. Disaster mitigation credit. . (c) Effective date The amendments made by this section shall apply to taxable years beginning after December 31, 2019.