30 January 2013
yes, if you want to revise a return then original return must be filed within time limit u/s 139(1) a return can be revised within one year from the end of relevant a/y
e.g. return for f/y 2010-11 was filed within time limit i.e. before july or september as the case may be.. then it can be revise upto 31st march 2013.