The Substantial Presence Test: How the IRS Determines U.S. Tax Residency
Why U.S. tax residency matters so much
The difference between being a U.S. tax resident and a nonresident alien is enormous. U.S. tax residents — whether citizens, green card holders, or individuals who meet the substantial presence test — are taxed on their worldwide income. Nonresident aliens are generally taxed only on U.S.-source income and income effectively connected with a U.S. trade or business. For a foreign national who spends significant time in the United States for work, family, or business reasons, the substantial presence test can unexpectedly trigger full U.S. tax liability on global income.
The substantial presence test formula
An individual meets the substantial presence test for a calendar year if they are present in the United States for at least 31 days during the current year, and the sum of the following weighted day count equals 183 or more: all days present in the current year, plus one-third of the days present in the first preceding year, plus one-sixth of the days present in the second preceding year.
For example, if an individual is present in the United States for 120 days in the current year, 120 days in the prior year, and 120 days in the year before that, the calculation is: 120 + (120 / 3) + (120 / 6) = 120 + 40 + 20 = 180 days. That falls just short of 183, and the test is not met. But if any of those year counts were slightly higher, the test would be triggered. The three-year lookback makes the test sensitive to patterns of presence that span multiple years, not just the current year.
Days that do not count
Not all days physically present in the United States count toward the substantial presence test. Exempt days include: days present as an exempt individual (foreign government employees under A or G visas, teachers and trainees under J or Q visas during the exempt period, students under F, J, M, or Q visas during the exempt period, and professional athletes temporarily in the U.S. for charitable events), days the individual was unable to leave the U.S. due to a medical condition that arose while present, and days in transit between two foreign locations if the individual was present in the U.S. for fewer than 24 hours.
Careful tracking of exempt days is essential for individuals who regularly travel to or through the United States. The burden of proving that days qualify as exempt falls on the taxpayer.
The closer connection exception
Even if the substantial presence test is technically met, an individual may avoid U.S. tax residency by claiming the closer connection exception — provided they were present in the U.S. for fewer than 183 days in the current year, maintained a tax home in a foreign country, and had a closer connection to that foreign country than to the United States. Factors considered in the closer connection analysis include the location of the individual's permanent home, family, personal belongings, business activities, and social ties. The exception is claimed by filing Form 8840 with the IRS.
Tax treaty tiebreaker provisions
If an individual is treated as a tax resident of both the United States (under the substantial presence test) and a foreign country (under that country's domestic law), an applicable income tax treaty may contain a tiebreaker provision that assigns residency to one country based on a hierarchy of factors: permanent home, center of vital interests, habitual abode, and nationality. Invoking a treaty tiebreaker requires filing Form 8833 with the U.S. tax return. Importantly, a treaty tiebreaker does not eliminate U.S. filing obligations — a U.S. citizen or green card holder cannot use a treaty tiebreaker to escape U.S. worldwide taxation.
If you spend significant time in the United States and are uncertain whether you meet the substantial presence test, our cross-border tax attorneys can analyze your day count, evaluate available exceptions, and help you structure your presence to achieve the most favorable tax result. Contact us to get started.
