This publication discusses special tax rules for U.S. citizens and resident aliens who work abroad or who have income earned in foreign countries. If you are a U.S. citizen or resident alien, your worldwide income is generally subject to U.S. income tax, regardless of where you are living. Also, you are subject to the same income tax filing requirements that apply to U.S. citizens or resident aliens living in the United States. Expatriation tax provisions apply to U.S. citizens who have renounced their citizenship and long-term residents who have ended their residency. These provisions are discussed in chapter 4 of Pub. 519, U.S. Tax Guide for Aliens. Resident alien. A resident alien is an individual who is not a citizen or national of the United States and who meets either the green card test or the substantial presence test for the calendar year.