(1) of section 139 read: Provided that on an application made in the prescribed manner, the Income Tax officer may, in his discretion, extend the date for furnishing the return (i) in the case of any person whose total income includes any income from business or profession the previous year in respect of which expired on or before the 31st day of December of the year immediately preceding the assessment year, and in the case of any person referred to in clause (b), up to a period not extending beyond the 30th day of September of the assessment year without charging any interest; (ii) in the case of any person whose total income includes any income from business or profession the previous year in respect of which expired after the 31st day of December of the year immediately preceding the assessment year, upto the 31st day of December of the assessment year without charging any interest; and (iii) up to any period falling beyond the dates mentioned in clauses (i) and (ii), in which case, interest at nine per cent per annum shall be payable from the 1st day of October or the 1st day of January, as the case may be, of the assessment year to the date of the furnishing of the return (a) in the case of a registered firm or an unregistered firm which has been assessed under cl.