Two general tests — a “Green Card” test and a “Substantial Presence test — can often determine if a non-citizen resident must file a U.S. tax return. The next question is whether the individual must file an IRS Form 1040 and pay taxes on all income including foreign income, or file a Form 1040-NR and pay taxes on only U.S. income. Filing a 1040-NR depends on whether the individual’s home country has a tax treaty with the U.S. and other factors that will establish that person’s tax “home.”See the JD Supra article