1. Short title This Act may be cited as the Revitalizing Economies, Housing, And Businesses Act of 2020 or as the REHAB Act of 2020 . 2. Modification of rehabilitation credit (a) Reinstatement of credit for qualified rehabilitated buildings (1) In general Subsection (a) of section 47 of the Internal Revenue Code of 1986 is amended to read as follows: (a) Determination of credit (1) In general For purposes of section 46, the rehabilitation credit for any taxable year is the sum of— (A) in the case of any qualified rehabilitated building other than a certified historic structure which is placed in service during such taxable year, 10 percent of the qualified rehabilitation expenditures with respect to such building, and (B) in the case of any qualified rehabilitated building which is a certified historic structure which is placed in service during such taxable year or any of the 4 immediately preceding taxable years, the ratable share for such taxable year. (2) Ratable share For purposes of paragraph (1)(B), the ratable share for any taxable year is an amount equal to 20 percent of the qualified rehabilitation expenditures with respect to the certified historic structure, as allocated ratably to each of the 5 years to which paragraph (1)(B) applies. . (2) Conforming amendments (A) Section 47(c) of such Code is amended— (i) in paragraph (1)— (I) in subparagraph (A), by amending clause (iii) to read as follows: (iii) in the case of any building other than a certified historic structure, in the rehabilitation process— (I) 50 percent or more of the existing external walls of such building are retained in place as external walls, (II) 75 percent or more of the existing external walls of such building are retained in place as internal or external walls, and (III) 75 percent or more of the existing internal structural framework of such building is retained in place, and , and (II) by redesignating subparagraphs (B) and (C) as subparagraphs (C) and (D), respectively, and by inserting after subparagraph (A) the following