What if i miss the 31st july 2013 dead line

As per the section 234 in the Income Tax Act, there are various penalties and implications attached to delay in filing or non-filing of your returns.

Interest under section 234 A for delay in filing of return after July 31
If you need to pay tax and have filed return after July 31 then you have to pay interest of 1 per cent for every month for the tax due for delay in filing of returns. For example, suppose you need to pay Rs. 50,000 as tax for the financial year 2012-13. Your company has deducted TDS of Rs. 30,000 and you didn't pay the remaining Rs. 20,000 within the due date. You have decided to file your return in the month of October 2013. Then you have to pay interest of Rs. 600 for the delay of return filing under section 234 A.