Special periods of assessment

(1) Where the Commissioner is satisfied that any person other than an employed person usually makes up the accounts of his or its trade or business of on some day other than the last day of a basis year the Commissioner shall permit the gains or profits of that trade or business to be computed for the purposes of this Act upon the income of the year terminating on that day in the basis year on which the accounts of the said trade or business have been usually made up. (2) In no case where the Commissioner has permitted the gains and profits of any trade or business to be computed on any date mentioned in sub-section (1) of this section, shall any change be subsequently made without prior notice in writing to the Commissioner and subject to such adjustment of income tax as the Commissioner may determine.