663. A beneficiary of a trust shall include, in computing his income for a particular taxation year,(a) in the case of a trust, other than a trust referred to in subparagraph a of the third paragraph of section 647, such part of the amount that, but for paragraphs a and b of section 657, would be the trust’s income for the trust’s taxation year that ended in the particular year as became payable in the trust’s taxation year to the beneficiary; and
(b) in the case of a trust governed by an employee benefit plan to which the beneficiary has contributed as an employer, such part of the amount that, but for paragraphs a and b of section 657, would be the trust’s income for its taxation year that ended in the particular year as was paid to the beneficiary in that taxation year of the trust;
(c) (paragraph repealed).