US Substantial Presence Test
If you are not a US citizen and not a green card holder, you may still be treated as a US tax resident if you spend enough time in the United States.
This is determined using the Substantial Presence Test (SPT).
You are considered a US tax resident for a given year if both conditions are met:
- You were in the US for at least 31 days during the current year
- Your weighted total days over a 3-year period is 183 days or more
How the 3-year calculation works
The US counts days using a weighted formula:
- All days present in the current year
- 1/3 of the days present in the previous year
- 1/6 of the days present in the year before that
If this total reaches 183 days or more, you meet the test.
Example
| Year | Days in US | Counted for SPT |
|---|---|---|
| 2025 (current) | 120 | 120 (full) |
| 2024 | 120 | 40 (1/3) |
| 2023 | 120 | 20 (1/6) |
| Total | — | 180 |
At 180 days, this person does not meet the test. At 183 or more, they would be considered US tax resident.
What counts as a "day" in the US?
Generally, any day you are physically present in the US counts, even partial days.
However, some days may be excluded, such as:
- Certain days in transit (less than 24 hours between foreign destinations)
- Days you are unable to leave due to a medical condition that arose while in the US
- Days you qualify as an "exempt individual" (for example, certain students, teachers, or diplomats)
What happens if you meet the Substantial Presence Test?
You are treated as a US tax resident for that year.
This usually means:
- You must report worldwide income to the IRS
- You may need to file additional forms about foreign bank accounts and assets (e.g., FBAR, FATCA reporting)
- You may owe US tax even on income earned outside the US
If you do NOT meet the test
You are generally treated as a non-resident alien for tax purposes.
In that case, you are usually taxed only on US-source income, such as:
- Income from US employment
- US rental income
- Certain US investment income
Tax treaties and exceptions
The US has tax treaties with many countries.
Even if you meet the Substantial Presence Test, you may be able to claim treaty benefits to be treated as a resident of another country under "tie-breaker" rules. This requires filing additional forms with the IRS.
Why this matters
It's easy to trigger US tax residency unintentionally by spending long periods in the country across multiple years.
Many people focus only on the current year and forget the rolling 3-year formula.
What Amanda does
Amanda helps you:
- Track your days in the US across multiple years
- Estimate when you are approaching the Substantial Presence Test threshold
- Understand when US tax residency exposure may arise
Amanda does not determine your legal tax status but helps you stay aware of potential exposure.
Official sources
For authoritative guidance, see:
- IRS Publication 519 — U.S. Tax Guide for Aliens
- Internal Revenue Code §7701(b)
These define how the Substantial Presence Test is applied by US tax authorities.