An assessee who is required to file a return of income is entitled to revise the return of income originally filed by him to make such amendments additions or changes as may be found necessary by him. Such a revised return may be filed by the assessee at any time before the assessment is made. There is no limit under the income tax Act in respect of the number of time for which the return of income may be revised by the assessee. However, if a person deliberately files a false return he will be liable to be imprisoned under section 277 and the offence will not be condoned by filing a revised return.
As per section 139(5), the revised return can be filed before the expiry of one year from the end of the relevant assessment year or before the completion of assessment, whichever is earlier. Thus return of A.Y 2011-12 can be revised till 31st March 2013 or before the completion of the assessment whichever is earlier.