03 July 2013
For AY 2010-11 and AY 2011-12 returns are time barred and can not be filed. . For AY 2012-13 and AY 2013-14 returns can be filed . . Due date for an Individual is 31-08-2012 for AY 2012-13 and 31-07-2013 for AY 2013-14. . For late filing of taxable returns penalty may be levied by the AO. . However, if you have no tax liability for the AY 2012-13, you can file the return.
03 July 2013
last date for valid return is one year from the end of relevant assessment year as per income tax act. penalty after end of assessment year COULD BE 5000 depending on A.O.. but after one year not possible to file. eg for A.Y. 2011-12 last date without interest 31st july 2011 (if audit 3o sep.) last date with interest 31st march 12 last date with interest and penalty of Rs 5000 is 31st march 2013. after that not possible to file. so you can file only for the A.Y. 2012-13 and 13-14 now
though some people use illegal means to file back date return but that is illegal and punishable.