Overview of U.S. Tax Residence Rules
The taxation of aliens by the United States is significantly affected by the residency status of such aliens.
Although the immigration laws of the United States refer to aliens as immigrants, non-immigrants, and undocumented (illegal) aliens, the tax laws of the United States refer only to ‘resident’ and ‘nonresident aliens’.
In general, the controlling principle is that ‘resident aliens’ are taxed in the same manner as U.S. citizens on their worldwide income, and ‘nonresident aliens’ are taxed according to special rules contained in certain parts of the Internal Revenue Code.