12(1)All such assessments or adjustments of assessments shall be made as may be necessary to give effect to a claim or the withdrawal of a claim.
(2)An assessment under this paragraph shall not be out of time if it is made—
(a)in the case of a claim, within one year from the date on which an assessment of the claimant company to corporation tax for the period for which the claim is made becomes final and conclusive, and
(b)in the case of the withdrawal of a claim, within one year from the date on which the claim is withdrawn.