38(1)For the purposes of paragraph 37, where there is a straddling period—U.K.
(a)so much of the straddling period as falls before the day on which this Act is passed, and so much of it as falls on or after that date, are to be treated as separate accounting periods or taxable periods (as the case may be), and
(b)if it is necessary to apportion an amount for the straddling period to the two separate periods, it is to be apportioned—
(i)on a time basis, according to the respective length of the separate periods, or
(ii)if that would produce a result that is unjust or unreasonable, on a just and reasonable basis.
(2)A “straddling period” is an accounting period or payment period (as the case may be) beginning before the day on which this Act is passed and ending on or after that date.