13(1)Where during or at the end of a period of account a company carrying on a trade ceases to do so, or ceases to be within the charge to corporation tax under Case I of Schedule D in respect of the trade, then, subject to paragraph 20 below—
(a)it shall not be entitled to relief in respect of that period; and
(b)a charge by way of recovery of relief shall be made on the company on an amount equal to the unrecovered past relief allowed to it for that trade.
(2)Sub-paragraph (1) above shall apply also where the scale of the activities of the trade for any period of account is negligible in comparison with their scale for any previous period of account beginning not more than six years before the first-mentioned period.
(3)Where during or at the end of a period of account a company carrying on a trade ceases (by virtue of ceasing to be resident in the United Kingdom) to be within the charge to corporation tax under Case I of Schedule D in respect of a part of the trade, it shall be treated for the purposes of this Schedule as if that part were a separate trade carried on by it in that period; and all necessary apportionments between the two parts of the trade (including the apportionment of unrecovered past relief allowed for that trade) shall be made by reference to the respective values of the trading stock of each part immediately after that event