139(5)

Section 139 sub 5  talks about  - If any person having furnished  a return under sub- section (1) or sub section (4) , discovers any omission or any wrong statement therein, he may furnish a revised retrun at any time before the expiry of one year form the end of the relevant assessment year or before the completion of the seeessment , whichever is earlier . so date will be for FY 2017-18 is 31/3/2019

So please confirm this before applying