23(1)In section 336 of the Income Tax Act 1952 there shall (except as regards expenditure incurred before 6th November 1962) be added at the end as subsection (6):—
“(6)Subsections (2) to (5) of this section shall apply only for purposes of income tax, and the relevant chargeable period for purposes of corporation tax shall be that in which the expenditure is incurred or, if it is incurred before the setting up and commencement of the trade, the chargeable period beginning when the trade is set up and commenced.”
(2)If, in the case of expenditure incurred by a company before 6th November 1962, the five years of assessment referred to in section 336(1) of the Income Tax Act 1952, have not expired at or before the end of the year 1965-66, allowances under that section shall be made for successive accounting periods without restriction of number, but so that—
(a)the allowance for an accounting period of less than a year shall be proportionately reduced; and
(b)the aggregate of the allowances in respect of any expenditure (whether for years of assessment or for accounting periods) shall not exceed the amount of the expenditure.
(3)Accordingly in section 268(4) of the [1952 c. 10.] Income Tax Act 1952, after the words " section 336 of this Act" there shall be inserted the words " as at the end of the chargeable period or, if it is a year of assessment ".