Yes, provided the original return has been filed before the due date and your assessment
has not been completed. It is expected that the mistake in the original return is
of a genuine and bonafide nature and not rectification of any deliberate mistake.
However, a belated return (a return filed after the due date) cannot be revised.
Return can be revised within a period of one year from the end of the relevant assessment
year or before completion of the assessment whichever is earlier. e.g., In case
of income earned during FY 2014-15, the due date of filing the return of income
(considering no extension) is 31st July, 2015. If the return of income is filed on or
before 31st July, 2015 then the return can be revised upto 31st March, 2017 (assuming
assessment is not completed by that date). However, if return is filed after 31st
July, 2015, then it will be a belated return and a belated return cannot be revised.