Your income tax return is due April 17 (you get two extra days this year). If you can't finish it by then, don't panic. You can get an automatic extension to file your return by Oct. 15, 2012.
However, obtaining an extension of time to file your return does not extend the time you have to pay any taxes due the Internal Revenue Service. Your tax payments (if any) are still due on April 17. So, if you do owe the IRS money, you'll need to estimate out how much and pay the amount before April 17. If you pay late, you'll be charged interest and possibly penalties as well.