(In the application of (a) of this subdivision, if the accumulated income of a trust is ultimately payable to the estate of the current income beneficiary or is ultimately payable to his appointees or takers in default of appointment, under a power of the type described in (a) of this subdivision, it need not be payable to the beneficiary from whom it was withheld under any circumstances. Furthermore, if a trust otherwise qualifies for the exception in (a) of this subdivision the trust income will not be considered to be taxable to the grantor under section 677 by reason of the existence of the power of appointment referred to in (a) of this subdivision.) In general, the exception in section 674(b)(6) is not applicable if the power is in substance one to shift ordinary income from one beneficiary to another. Thus, a power will not qualify for this exception if ordinary income may be distributed to beneficiary A, or may be added to corpus which is ultimately payable to beneficiary B, a remainderman who is not a current income beneficiary. However, section 674(b)(6)(B), and (c) of this subdivision, permit a limited power to shift ordinary income among current income beneficiaries, as illustrated in example 1 of this subparagraph.
26 C.F.R. §1.674(b)-1