(1) For the purposes of group relief, any accounting period of the claimant company which falls wholly or partly within an accounting period of the surrendering company shall correspond to that accounting period.
(2) Where an accounting period of the surrendering company and a corresponding accounting period of the claimant company do not coincide -
(a)the amount which may -
(i) be set off against the total profits under section 420,
(ii) under subsection (3) of section 420A, be set off against income specified in subparagraph (i), (ii) or (iii) of paragraph (a) of that subsection, or
(iii) reduce the relevant corporation tax under subsection (3) of section 420B,
of the claimant company for the corresponding accounting period, shall be reduced by applying the fraction -
(if that fraction is less than unity), and
(b) the amount of -
(i) the total profits against which the amount mentioned in paragraph (a)(i) (as reduced where so required) may be set off,
(ii) the income against which t
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