(1) For the purposes of Case I or II of Schedule D the profits or gains of a trade or profession carried on by a company shall be computed in accordance with generally accepted accounting practice subject to any adjustment required or authorised by law in computing such profits or gains for those purposes.

(2) Schedule 17A shall apply to a company as respects any matter related to the computation of income of the company where as respects that matter -

(a) for an accounting period profits or gains of a trade or profession carried on by the company are computed in accordance with relevant accounting standards (within the meaning of that Schedule), and

(b) for preceding accounting periods profits or gains of a trade or profession carried on by the company are computed in accordance with standards other than relevant accounting standards (within the meaning of that Schedule).

(3)

(a) In this subsection -

(i) 'accounting policy', 'a change in accounting policy', 'accounting standard', 'retrospective' and 'opening reserves' shall be construed in accordance with generally accepted accounting practice;

(ii) 'relevant period' means the accounting period beginning on the first day of the period of account in which the change in accounting policy, referred to in paragraph (b), is adopted for the first time.