If you believe that you will not be able to file your tax return by the due date (generally April 15) you can apply for an automatic six-month extension of time to file, by filing Form 4868, Application for Automatic Extension of Time to File U.S. Individual Income Tax Return. With the 6-month extension, you must file your tax return by October 15.
It is very important to note that when you file for an extension, you are only requesting an extension of time to file, and NOT an extension of time to pay. Therefore, you have an obligation to make an accurate estimate of your tax liability for the year, and pay the amount due by regular due date (April 15). If you do not pay the taxes due, you could be hit with a penalty. Read more