Every U.S. citizen - regardless of whether they are living in the U.S. or abroad - must file a tax return with the federal government and report their world wide income . Even some states require that you file a tax return when living abroad. Who is an Expatriate ? American U.S. citizens and Green Card holders living outside the U.S. Due Dates : April 15 - Tax payment deadline. June 15 - Tax filing deadline. An extension can be filed to extend the filing deadline to October