28 August 2010
As per Sec 139(5) If any person, having furnished a return under sub-section (1), or in pursuance of a notice issued under sub-section (1) of section 142, discovers any omission or any wrong statement therein, he may furnish a revised return at any time before the expiry of one year from the end of the relevant assessment year or before the completion of the assessment, whichever is earlier:
So, you can file Revised Return till 31st March 2011 or date of assessment made by department under section 143(3), 144, 147, whichever is earlier.
So if no assessment is made by the department before 31st MAch2011. ITR can be revised til 31st Mar 2011