Paragraph 48
This paragraph applies if—
a period of account of a trade, profession or vocation begins before 6th April 2005 and ends on or after that date,
the period of account, or part of the period of account, falls in the basis period for the tax year 2005-06,
part of the period of account also falls in the basis period (or periods) for an earlier tax year (or years), and
in order to arrive at the profits or losses of the basis period for any earlier tax year it is necessary to apportion the profits or losses of the period of account to any part of the period of account falling in that basis period.
The profits or losses of the period of account—
are calculated in accordance with Part 2 of this Act (and therefore, to that extent, that Part has effect for tax years before the tax year 2005-06), and
may be apportioned in accordance with section 203 to any part of the period of account falling in a basis period for a tax year before the tax year 2005-06.