Judgment

DUTT, J. :- The appellants, who are all registered firms within the meaning of S. 2(39), Income-tax Act, 1961, hereinafter referred to as the Act, have preferred these appeals against the judgments of the Gauhati High Court overruling the challenge of the appellants as to the legality of the interest charged by the Income-tax Officer for the delayed filing of returns and also as to the constitutional validity of sub-s. (4) of S. 139 of the Act, as it stood before April 1, 1971.

2. The relevant provisions of S. 139, as it stood prior to April 1, 1971, are as follows : -

"S. 139(1). Every person, if his total income ......... during the previous year exceeded the maximum amount which is not chargeable to income-tax, shall furnish a return of his income ...................

(a) in the case of every person .............. before the expiry of six months from the end of the previous year................, or before the 30th day of June of the assessment year, whichever is later;

(b) in the case of every other person, before the 30th day of June of the assessment year :

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 cl. (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, up to 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. (b) of S. 183, on the amount of tax which would have been payable if the firm had been assessed as an unregistered firm, and

(b) in any other case, on the amount of tax payable on the total income,

reduced by the advance tax, if any, paid or by any tax deducted at source, as the case may be.

(2). In the case of any person, who in the Income-tax Officers opinion, is assessable under this Act, whether on his own total income or on the total income of any other person during the previous year, the Income-tax Officer may, before the end of the relevant assessment year, serve a notice upon him requiring him to furnish, within thirty days from the date of service of the notice, a return of his income or the income of such other person during the previous year, in the prescribed form and verified in the prescribed manner setting forth with such other particulars as may be prescribed :

Provided that on an application in the prescribed manner the Income-tax Officer may, in his discretion, extend the date for the furnishing of the return, and when the date for furnishing the return, whether fixed originally or on extension, falls beyond the 30th day of September or, as the case may be, the 31st day of December of the assessment year, the provisions of sub-cl. (iii) of the proviso to sub-s. (1) shall apply.

(4). Any person who has not furnished a return within the time allowed to him under sub-s. (1) or sub-s. (2) may before the assessment is made furnish the return for any previous year at any time before the end of four assessment years from the end of the assessment year to which the return relates, and the provisions of sub-cl. (iii) of