(1)This section applies if—
(a)expenses of the trustees are to be used to reduce the beneficiary's income for income tax purposes, and
(b)a proportion of the beneficiary's income is untaxed income (see section 502).
(2)A proportion of those expenses is not to be so used.
(3)That proportion is the same as the proportion of the beneficiary's income which is untaxed income.
(4)In subsection (3) the references to the beneficiary's income and untaxed income do not, in either case, include so much (if any) of that income as is equal to the amount of income tax, or of any foreign tax, for which the trustees are liable on that income.
(5)“Foreign tax” means any tax which—
(a)is of a similar character to income tax, and
(b)is imposed by the laws of a territory outside the United Kingdom.