(1) Section 958 of the Principal Act is amended -

(a) in subsection (1) -

(i) in paragraph (a) -

(I) by inserting the following definition after "corres ponding corporation tax for the preceding chargeable period":

"'corresponding income tax for the preceding chargeable period', in relation to a chargeable period which is an accounting period of a company, means an amount determined by the formula -

where -

I is the income tax payable under section 239 or 241 by the chargeable person for the preceding chargeable period,

C is the number of days in the chargeable period, and

P is the number of days in the preceding chargeable period;",

(II) by substituting the following for the definition of "tax payable for the initial period":

"'tax payable for the initial period', in relation to a chargeable period which is -