this paragraph for any taxable year shall be made not later than the time for filing the return of tax for such year (including extensions), shall be made on such return, and shall be made in such manner as the Secretary shall prescribe. Such an election, once made, shall be irrevocable. . (d) Effective date The amendments made by this section shall apply to taxable years beginning after December 31, 2017. 13402. Rehabilitation credit limited to certified historic structures (a) In general Subsection (a) of section 47 is amended to read as follows: (a) General rule (1) In general For purposes of section 46, for any taxable year during the 5-year period beginning in the taxable year in which a qualified rehabilitated building is placed in service, the rehabilitation credit for such year is an amount equal to the ratable share for such year. (2) Ratable share For purposes of paragraph (1), the ratable share for any taxable year during the period described in such paragraph is the amount equal to 20 percent of the qualified rehabilitation expenditures with respect to the qualified rehabilitated building, as allocated ratably to each year during such period. . (b) Conforming amendments (1) Section 47(c) is amended— (A) in paragraph (1)— (i) in subparagraph (A), by amending clause (iii) to read as follows: (iii) such building is a certified historic structure, and , (ii) by striking subparagraph (B), and (iii) by redesignating subparagraphs (C) and (D) as subparagraphs (B) and (C), respectively, and (B) in paragraph (2)(B), by amending clause (iv) to read as follows: (iv) Certified historic structure Any expenditure attributable to the rehabilitation of a qualified rehabilitated building unless the rehabilitation is a certified rehabilitation (within the meaning of subparagraph (C)). . (2) Paragraph (4) of section 145(d) is amended— (A) by striking of section 47(c)(1)(C) each place it appears and inserting of section 47(c)(1)(B) , and (B) by striking section 47(c)(1)(C)(i) and inserting section 47(c)(1)(B)(i) . (c)