If a person after furnishing the return finds any mistake, omission or any wrong statement, then return should be revised within prescribed time limit.
A return can be revised at any time 3 months before the end of the Assessment Year or before the completion of the assessment; whichever is earlier.
If original return has filed in paper format or manually, then technically it cannot be revised by online mode or electronically.
Revised return can be filed online under section 139(5).
Source: Income Tax India’s Official Website
