Dear Mr. banerji,
You have to file the belated return/revised return for FY 2015-16 and show the capital gain tax amount in the return. The last date of filing of this return is 31 March 2017.
To calculate capital gain tax we need date and cost of acquisition and also details of improvement in the property.
Please feel free to call/revert in case of any doubts
Thanks and Regards
Abhishek Dugar
CA CS B.Com