period, (B) 25 percent for the 3d and 4th calendar quarters of the phaseout period, and (C) 0 percent for each calendar quarter thereafter. (4) Controlled groups Rules similar to the rules of section 30B(f)(4) shall apply for purposes of this subsection. (f) Application of certain rules Rules similar to the rules of section 30D(f) shall apply for purposes of this section. . (b) Credit made part of general business credit 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 portion of the new qualified natural gas motor vehicle credit to which section 30E(c)(1) applies. . (c) Conforming amendments (1) Section 1016(a) of such Code is amended by striking and at the end of paragraph (37), by striking the period at the end of paragraph (38) and inserting , and , and by adding at the end the following new paragraph: (39) to the extent provided in section 30E(f). . (2) Section 6501(m) of such Code is amended by inserting 30E(f), after 30D(e)(4), . (3) The table of sections for subpart B of part IV of subchapter A of chapter 1 of such Code is amended by adding at the end the following new item: Sec. 30E. New qualified natural gas motor vehicles. . (d) Effective date The amendments made by this section shall apply to taxable years beginning after December 31, 2017. 5. Extension and increase of alternative fuel vehicle refueling property credit (a) Extension of credit Section 30C(g) of the Internal Revenue Code of 1986 is amended by striking December 31, 2017 and inserting December 31, 2022 . (b) Modification of dollar limitation Section 30C(b)(1) of such Code is amended by striking $30,000 and inserting $100,000 . (c) Effective dates (1) Extension of credit The amendment made by subsection (a) shall apply to property placed in service after December 31, 2017. (2) Modification of dollar limitation The amendment made by subsection (b) shall apply to taxable