respect to any trade or business referred to in section 382(d)(4)(B)(i) for any start-up period taxable year, the amount which bears the same ratio to the unused general business credit which arose in such start-up period taxable year as— (A) the amount of the general business credit which would have been determined for such start-up period taxable year if only credits properly allocable to such trade or business were taken into account, bears to (B) the amount of the general business credit determined for such start-up period taxable year. (4) Application of certain rules Rules similar to the rules of subparagraphs (C)(ii), (D), (E), and (F) of section 382(d)(4) shall apply for purposes of this subsection. (5) Transition rule This subsection shall not apply with respect to any trade or business if the date on which such trade or business begins as an active trade or business (as determined under section 195(d)(2) without regard to subparagraph (B) thereof) is on or before September 10, 2018. . (c) Effective date The amendments made by this subsection shall apply to taxable years ending after September 10, 2018.