If any person, having furnished a return u/s 139(1), or in pursuance of a notice issued under section 142(1), 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. A return filed late u/s 139(4) cannot be revised.
A second revised return can be filed u/s 139(5) correcting omissions or wrong statements made in the first revised return; as the first revised return filed under section 139(5) would, in law, be a return u/s 139(1) also. The period of imitation prescribed under section 153(1) will run from the date of filing of second revised return, if the assessee has filed two revised returns. [Niranjan Lal Ram Chandra Vs. CIT. (1982) 134 ITR 352(AIL)] [Golden Insulation and Engg. Ltd. Vs. CIT  165 Taxman 105 (Delhi).