(a) In general. Sections 1.245A-6 through 1.245A-11 apply to taxable years of a foreign corporation beginning on or after December 1, 2020 and to taxable years of section 245A shareholders in which or with which such taxable years end.

(b) Exception. Notwithstanding paragraph (a) of this section, a taxpayer may choose to apply §§ 1.245A-6 through 1.245A-11 for a taxable year of a foreign corporation beginning before December 1, 2020 and to a taxable year of a section 245A shareholder in which or with which such taxable year ends, provided that the taxpayer and all persons bearing a relationship to the taxpayer described in section 267(b) or 707(b) apply §§ 1.245A-6 through 1.245A-11, in their entirety, and § 1.6038-2(f)(18) for all such taxable years and any subsequent taxable years beginning before December 1, 2020.