14 March 2017
Last date for filing belated or revised return is one year from the end of relevant assessment year For FY 2014-15, assessment year is 2015-16 and one year from end of that i.e one year from 31st march 2016. accordingly, Income tax return for FY 2014-15 can be filed only till 31st March 2017 and not after that.
Income tax return for FY 15-16 can be filed till 31st March 2018, so you can file that even after 31st March 2017.