The US Substantial Presence Test
The United States does not use a simple 183-day rule. It uses the Substantial Presence Test (SPT), which weights your days across three years — so you can meet it even in a year when you spent well under 183 days in the US.
This page explains the formula step by step. To run it on your own trips, use the free Substantial Presence Test calculator linked below.
Run the weighted three-year US formula on your own trips — free, no login.
How is the Substantial Presence Test calculated?
You meet the test if two conditions are both true. First, you were present in the US at least 31 days in the current year. Second, your weighted three-year total reaches 183 days: count all your days this year, plus one-third of last year’s days, plus one-sixth of the days from the year before. If that total is 183 or more — and you meet the 31-day minimum — you are generally a US tax resident for the year.
Why can I meet it on fewer than 183 days in a year?
Because prior years are added in. Roughly 122 days a year, repeated, is enough to trip the test over time (122 + 122/3 + 122/6 ≈ 183). That is why the SPT catches people who assume the “half the year” rule of thumb protects them — days from the previous two years still count.
Are there exceptions to the test?
Yes. The closer-connection exception, days-in-transit and certain medical-condition exclusions, and “exempt individual” categories (some students, teachers and diplomats) can change the result, and a tax treaty may override it. This page and the calculator handle the day count; confirm the exceptions with the IRS or a US tax professional.
Countries that use this rule
Jurisdictions we track that use a weighted multi-year presence test.
Frequently asked questions
What is the US Substantial Presence Test?
It is the day-count test the US uses to decide tax residency. You meet it if you are present at least 31 days in the current year and your weighted three-year day total (current year + 1/3 of last year + 1/6 of the year before) is 183 or more.
How many days can I spend in the US without becoming a tax resident?
As a rough guide, staying under about 122 days every year keeps the weighted three-year total under 183. But exceptions (closer connection, exempt individuals, treaties) can change the outcome — run the full formula and confirm with the IRS.
Other rule guides
Track this rule against your own days
Yuravia counts your days in every country and warns you before you cross a threshold. Free, anonymous, no ads.
Create your free account