665. A taxpayer who has included in computing his income for a taxation year, under section 663 or 684, an amount in respect of his income interest in the trust may deduct, for the same year, except to the extent that an amount in respect thereof has been deducted in computing his taxable income pursuant to section 738 or 845, the lesser of such amount and the excess of the cost of his interest over the aggregate of the amounts deductible as such under this section in computing his income for previous taxation years.
1972, c. 23, s. 503; 1984, c. 15, s. 144; 1988, c. 18, s. 57; 1989, c. 5, s. 77.