951 / What is the difference between a resident alien and a nonresident alien?
A foreign individual who is not a U.S. citizen is labeled as an “alien” for U.S. tax purposes. An alien is either a nonresident alien or a resident alien. A resident alien is a foreign individual who meets either the green card test or the substantial presence test, discussed below, and a nonresident alien is any other foreign individual unless that individual is otherwise eligible to elect to be treated as a resident alien.
A foreign individual meets the “green card test” if given permission to reside in the U.S. on a permanent basis by U.S. Citizenship and Immigration Services (or a predecessor) and such permission has not been revoked or judicially determined to have been abandoned by the individual.1
A foreign individual meets the “substantial presence test” if physically present in the U.S. for at least (1) 31 days in 2025 and (2) 183 days during the three-year period that includes 2025, 2024 and 2023, counting only a certain number of days that the individual is present in the U.S. per year, based on the following table:2
| Year | Days Counted Toward 183 Day Total |
| 2025 | All days present in the U.S. |
| 2024 | 1/3 of days present in the U.S. |
| 2023 | 1/6 of days present in the U.S. |