Every taxpayers should be filed income tax returns in within due dates.it is not mean if you missed the due dates in any reason you will not able to file your tax returns.
But it can be filed within one year from the end of the assessment of year for which you want to file return.other wise Rs. Five Thousand can be charged by the income tax department as penalty from you.
If you file your return late i.e. after due date you can not revised your return if you found that some of the income declaration you missed.
other than above you you will receive your refund late and you will also loss of interest thereon
If you filed your loss return after due date you will not able to claim the same in next year
So beware and keep your priority in mind and file within due date