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.
When you file for an extension, you should enter any payment you enclose with Form 4868 on Form 1040. If you cannot pay the full amount of the tax you owe, you can still get the extension, but you may owe interest on the unpaid amount, and possibly a penalty for paying late.
If you are outside of the U.S. you are allowed an automatic two-month extension to file and pay federal income tax due if:
• You are a US citizen or resident, and on the regular due date of the tax return, you are living outside the US and Puerto Rico, and your main place of business or post of duty is outside the US and Puerto Rico.
• You are a US citizen or resident, and you are in military or naval service, on active duty outside the US and Puerto Rico.