Where an election is made under section 6163(a) to postpone payment of the tax imposed by section 2001, or 2101, such part of any estate, inheritance, legacy, or succession taxes allowable as a credit under section 2014, as is attributable to a reversionary or remainder interest may be allowed as a credit against the tax attributable to such interest, subject to the limitations on the amount of the credit contained in such sections, if such part is paid, and credit therefor claimed, at any time before the expiration of the time for payment of the tax imposed by section 2001 or 2101 as postponed and extended under section 6163.