A person who is not a U.S. citizen or green card holder is a U.S. resident for tax purposes for a calendar year if they meet the substantial presence test that year. The test has two parts, and both must be met.
- You were physically present in the United States on at least 31 days during the current year.
- You were present for at least 183 days during the 3-year period that includes the current year and the 2 years before it, counting all days in the current year, one-third of the days in the first year before, and one-sixth of the days in the second year before.
Worked example
A person was present in the United States for 120 days in each of 2023, 2024 and 2025. For 2025 the count is 120 days in 2025, plus 40 days (one-third of 120 for 2024), plus 20 days (one-sixth of 120 for 2023), which is 180. Because 180 is less than 183, the person does not meet the substantial presence test for 2025. Try your own numbers in the calculator.
What counts as presence
- Any day you are physically present in the United States counts, even part of a day, unless an exception applies.
- The United States includes the 50 states, the District of Columbia, U.S. territorial waters, and certain adjacent seabed and subsoil. It does not include U.S. territories or U.S. airspace.
- Some days are not counted. See the guide on days that do not count.
If you meet the test
Meeting the test does not always make you a resident alien. You may still be treated as a nonresident if you qualify for the closer connection exception, which is claimed on Form 8840.
Updated: November 4, 2026