Section 1.59A-10 - Applicability date(a)General applicability date. Sections 1.59A-1 through 1.59A-9 , other than the provisions described in the first sentence of paragraph (b) of this section, apply to taxable years ending on or after December 17, 2018. However, taxpayers may apply these regulations in their entirety for taxable years beginning after December 31, 2017, and ending before December 17, 2018. In lieu of applying the regulations referred to in the first sentence of this paragraph, taxpayers may apply the provisions matching §§ 1.59A-1 through 1.59A-9 from the Internal Revenue Bulletin (IRB) 2019-02 (https://www.irs.gov/irb/2019-02_IRB) in their entirety for all taxable years beginning after December 31, 2017 and ending on or before December 6, 2019.(b)Exception. Sections 1.59A-2(c)(2)(ii) and (c)(4) through (6) , 1.59A-3(b)(3)(iii)(C) , 1.59A-3(c)(5) and (6) , and 1.59A-9(b)(4) apply to taxable years beginning on or after October 9, 2020, and §§ 1.59A-7(c)(5)(v) and 1.59A-9(b)(5) and (6) apply to taxable years ending on or after December 2, 2019. Taxpayers may apply those regulations in their entirety for taxable years beginning after December 31, 2017, and before their applicability date, provided that, once applied, taxpayers must continue to apply them in their entirety for all subsequent taxable years. Alternatively, taxpayers may apply only § 1.59A-3(c)(5) and (6) for taxable years beginning after December 31, 2017, and before their applicability date, provided that, once applied, taxpayers must continue to apply § 1.59A-3(c)(5) and (6) in their entirety for all subsequent taxable years.T.D. 9910, 85 FR 64368 , Oct. 9, 2020 T.D. 9885, 84 FR 67017 , 12/6/2019; 85 FR 64368 , 12/8/2020