In the event that subparagraph (A) would apply, but for the fact that there is no living transferor, then each beneficiary of such trust, other than a contingent beneficiary, shall be treated as having income for the taxable year equal to— (i) the aggregate increases in the tax imposed under this title for each such prior taxable year (beginning after the date of the enactment of this chapter) which would have occurred if paragraph (1) had applied to such trust, but only to the extent of such increases in tax which would have occurred with respect to such portion of trust assets as are distributable to the beneficiary, or such portion of trust income as is distributable to the beneficiary (whether or not such assets or income are so distributed), plus (ii) interest on such increase determined with respect to each such taxable year determined at the underpayment rate. (C) Contingent beneficiaries In the event that no tax is imposed on a beneficiary under subparagraph (B) because such beneficiary is contingent, then in the first taxable year in which such beneficiary is no longer contingent, such beneficiary shall be treated as having income for the taxable year equal to the amount that would have been imposed under subparagraph (B), plus interest on such increase determined with respect to each such taxable year determined at the underpayment rate, but in no case will such tax and interest be imposed with respect to any portion of trust assets or income previously subject to tax under this section. (D) Contingent For purposes of this paragraph, a beneficiary’s interest in a trust shall be treated as contingent if (and only if) such interest depends on the outcome of uncertain future events (other than the discretion of the trustee to determine the timing of the distribution of income). (h) Election To pay liability in installments (1) In general A taxpayer may elect to pay the tax imposed under subsection (a) or (g) for any taxable year in 5 equal annual installments (in the case of the taxpayer’s first taxable