158.4. The amount to which section 158.3 refers for a taxation year in respect of a taxpayer’s matchable expenditure is the amount that is the least of(a) the aggregate of the amount by which the amount determined under this subparagraph for the preceding taxation year in respect of the matchable expenditure exceeds the amount of the matchable expenditure deductible in computing the taxpayer’s income for that preceding year and the lesser ofi. 1/5 of the matchable expenditure, and
ii. the amount determined by the formula
(A / B) × C;
(b) the aggregate of all amounts each of which is included in computing the taxpayer’s income for the year, other than any portion of such amount that is the subject of a reserve claimed by the taxpayer for the year under this Act, in respect of the right to receive production to which the matchable expenditure relates and the amount by which the amount determined under this subparagraph for the preceding taxation year in respect of the matchable expenditure exceeds the amount of the matchable expenditure deductible in computing the taxpayer’s income for that preceding year; and
(c) the amount by which the aggregate of all amounts each of which is the amount of the matchable expenditure that would, but for this division, have been deductible in computing the taxpayer’s income for the year or a preceding taxation year exceeds the aggregate of all amounts each of which is the amount of the matchable expenditure deductible under section 158.3 in computing the taxpayer’s income for a preceding taxation year.
In the formula provided for in subparagraph a of the first paragraph,(a) A is the number of months that are in the taxation year and after the day on which the right to receive production to which the matchable expenditure relates is acquired;
(b) B is the lesser of 240 and the number of months that are in the period that begins on the day on which the right to receive production to which the matchable expenditure relates is acquired and that ends on the day the right is to terminate; and
(c) C is the amount of the matchable expenditure.