This section applies for calculating the amount of income charged under section 579 other than annual payments.

Expenses wholly and exclusively incurred for the purpose of generating the income are deductible.

If an expense is incurred for more than one purpose, a deduction may be made for any identifiable part or identifiable proportion of the expense which is incurred wholly and exclusively for the purpose of generating the income.

Expenses which would not have been allowable as a deduction in calculating the profits of a trade, if they had been incurred for its purposes, are not deductible under this section.

Expenses for which any kind of relief is given under any other provision of the Income Tax Acts are not deductible under this section.

The relief given under section 600 (relief for expenses: patent income) is additional to the relief under this section.

The frequency with which payments are made is ignored in determining whether they are annual payments for the purposes of subsection (1).