(a) Tax attributable to amounts treated as received in preceding taxable years. If a taxpayer elects to compute the tax, on amounts deemed distributed under section 666, by the exact throwback method provided in section 669(a)(1)(A), the tax liability of the beneficiary for the taxable year in which the accumulation distribution is paid, credited, or required to be distributed is computed as provided in paragraph (b) of this section. The beneficiary may not elect to use the exact throwback method of computing his tax on an accumulation distribution as provided in section 669(a)(1)(A) if he were not alive on the last day of each preceding taxable year of the foreign trust created by a U.S. person with respect to which a distribution is deemed made under section 666(a). Thus, if a portion of an amount received as an accumulation distribution was accumulated by the trust during years before the beneficiary was born, the beneficiary is not permitted to elect the exact throwback method provided in section 669(a)(1)(A). See § 1.669(a)-4 for the computation of the tax on an accumulation distribution by the short-cut throwback method provided in section 669(a)(1)(B) under these circumstances.

(b) Computation of tax. The tax referred to in paragraph (a) of this section is computed as follows:

(1) First, compute the tax attributable to the section 666 amounts for each of the preceding taxable years. To determine the section 666 amounts attributable to each of the preceding taxable years, see § 1.666(a)-1. The tax attributable to such amounts in each such preceding taxable year is the difference between the tax for such preceding taxable year computed with the inclusion of the section 666 amounts in gross income, and the tax for such year computed without including them in gross income. Tax computations for each preceding year shall reflect the taxpayer's marital and dependency status for that year.

(2) Second, add

(i) The sum of the taxes for the preceding taxable years attributable to the section 666 amounts (computed in accordance with subparagraph (1) of this paragraph), and

(ii) The tax for the taxable year of the beneficiary in which the accumulation distribution is paid, credited, or required to be distributed to him, computed without including the section 666 amounts in gross income.

(c) Effect of prior election. In computing the tax attributable to an accumulation distribution for the taxable year in which such accumulation distribution is paid, credited, or required to be distributed to him, the beneficiary in computing the tax attributable to section 666 amounts for each of the preceding taxable years, must include in his gross income for each such year the section 666 amounts deemed distributed to him in such year resulting from prior accumulation distributions made to him in taxable years prior to the current taxable year. These section 666 amounts resulting from such prior accumulation distributions must be included in the gross income for such preceding taxable year even though the tax on the accumulation distribution of such prior taxable year was computed by the short-cut throwback method provided in section 669(a)(1)(B) and § 1.669(a)-4.