1(1)The investment income of an individual arising under a trust shall be ascertained without regard to any part of it shown to the satisfaction of the Board to be attributable to payments duly made otherwise than out of the income of the trust.
(2)For the purposes of this paragraph the income of a trust shall be ascertained without regard to—
(a)income or deductions of any description which, under section 42 of this Act, are to be left out of account in ascertaining aggregate investment income, or
(b)income from another trust which is shown to the satisfaction of the Board to be attributable to payments duly made otherwise than out of the income of that trust,
and no deduction shall be made in respect of any payment made to a beneficiary under the trust or to any person claiming under such a beneficiary.