; and (B) by striking $5 and inserting $100 . (2) Adjustment for inflation Section 5811 of the Internal Revenue Code of 1986 is amended by adding at the end the following new subsection: (d) Adjustment for inflation In the case of any taxable year beginning in a calendar year after 2019, each dollar amount in subsection (a) shall be increased by an amount equal to— (1) such dollar amount, multiplied by (2) 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 2018 for calendar year 2016 in subparagraph (A)(ii) thereof. If any increase under paragraph (1) is not a multiple of $5, such increase shall be rounded to the next lowest multiple of $5. . (c) Certain semiautomatic pistols chambered for cartridges treated as firearms The first sentence of section 5845(a) of the Internal Revenue Code of 1986 is amended— (1) by striking and before (8) ; (2) by striking device. and inserting device, and ; and (3) by adding at the end the following: (9) a semiautomatic pistol chambered for cartridges commonly considered rifle rounds, configured with receivers commonly associated with rifles and capable of accepting detachable magazines. . (d) Effective dates (1) In general Except as provided by paragraph (2), the amendments made by this section shall take effect on January 1, 2019. (2) In general The amendments made by subsection (a) shall take effect on July 1, 2019. (3) All taxpayers treated as commencing in business on July 1, 2019 Any person engaged on July 1, 2019, in any trade or business which is subject to an occupational tax by reason of the amendment made by subsection (a) shall be treated for purposes of such tax as having first engaged in a trade or business on such date.