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 without requesting an extension. For a calendar year return, the automatic 2-month extension is to June 15. Note that you must pay any tax due by April 15 or interest will be charged starting from April 15.
Where to File
If you are a U.S. citizen or resident alien (including a green card holder) and you live in a foreign country, mail your U.S. tax return to:
Department of the Treasury
Internal Revenue Service Center
Austin, TX 73301-0215
Electronic Filing (e-file)
Taxpayers with an AGI (Adjusted Gross Income) within a specified threshold can electronically file their tax return for free using Free File. Taxpayers with an AGI greater than the specified threshold can either use the Free File Fillable Forms or e-file by purchasing commercial software. A limited number of companies provide software that can accommodate foreign addresses.
Source: IRS: www.irs.gov