Can a return be filed after the due date?
Return of income which has not been furnished on or before the due date specified under section 139(1) is called belated return. Belated return of income is furnished under section 139(4).
Any person who has not furnished a return of income within the time period allowed under section 139(1) or within the time period allowed under a notice issued under section 142(1), may furnish return for any previous year 
- at any time 3 months before the end of the relevant assessment year or before completion of the assessment, whichever is earlier.                      
However, a belated return attracts late filing fees under section 234F. 
As per section 234F, late filing fees of Rs.5,000 shall be payable if return furnished after due date specified under section 139(1). However amount of late filing fees to be paid shall be Rs.1,000, if the total income of the person does not exceed Rs.5 lakhs.