U.S. Citizens and Resident Aliens Abroad
If you are a U.S. citizen or resident alien, the rules for filing income, estate, and gift tax returns and paying estimated tax are generally the same whether you are in the United States or abroad. Your worldwide income is subject to U.S. income tax, regardless of where you reside.
When to File
If you are a U.S. citizen or resident alien residing overseas, or are in the military on duty outside the U.S., on the regular due date of your return, you are allowed an automatic 2-month extension to file your return and pay any amount due without requesting an extension. For a calendar year return, the automatic 2-month extension is to June 15.
If you are unable to file your return by the automatic 2-month extension date, you can request an additional extension to October 15 by filing Form 4868, Application for Automatic Extension of Time To File U.S. Individual Income Tax Return, before the automatic 2-month extension date. However, any tax due payments made after June 15 will be subject to both interest charges and failure to pay penalties.
http://www.irs.gov/Individuals/International-Taxpayers/U.S.-Citizens-and-Resident-Aliens-Abroad
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