Answered on December 29,2017
Original return can be revised under section 139(5) within a period of one year from the end of the relevant assessment year or before completion of the assessment whichever is earlier if person furnished original return on or before the due (till assessment year 2016-17). In assessment year 2017-18, any original return (which is furnished on or before or after due date) 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.
From the assessment year 2018-19 return of income can be revised (original return is filed on or before due date of after due date) at any time during the assessment year or before the assessment made whichever is earlier.
If original return has filed in paper format or manually, then technically it cannot be revised by online mode or electronically.
If a person is furnished original return and finds any mistake, omission or any wrong statement, then return should revised within prescribed time limit