US Substantial Presence Test explained

The two conditions

You meet the day-count test for a calendar year if both of these are true:

• You were present in the United States for at least 31 days during the current year.
• Your weighted total over three years is at least 183 days.

The weighted total is every day in the current year, plus one third of the days in the previous year, plus one sixth of the days in the year before that. The calendar year runs from 1 January to 31 December.

How days are counted

Any part of a day in the United States counts as a full day for this test, including arrival and departure days. Days spent outside the United States do not count. You add up the days for each of the three years separately and then apply the weights.

Worked examples for 2026

Both examples test the year 2026.

In Example A, 120 days in each of three years sounds like a lot, but 120 + 40 + 20 is 180, just under the threshold. In Example B the person spent fewer days than a full half-year in 2026 and still met the test, because the prior years add 70 weighted days. You can check your own figures in the US 183-day calculator, which shows each year’s days and the weighted total.

Days that may not count

Some days can be excluded from the count. Days as an exempt individual, days of travel that qualify as transit, days when you could not leave because of a medical condition that arose in the United States, and days under certain visa categories may not count. The calculator does not evaluate these exclusions, so a result may overstate your counted days if any of them apply.

Planning to stay under the threshold

The test can also be run forward. Suppose you spent 120 days in the United States in each of 2024 and 2025. Those years contribute 20 and 40 weighted days, or 60 in total, so the current year can contain at most 122 days before the total reaches 183: 122 + 40 + 20 is 182, and 123 days would make 183.

That arithmetic only covers the day-count step. Whether you want to stay under the number, and what follows if you reach it, depends on your tax position, so use the figure as a planning input and confirm it with an adviser or the IRS pages linked below.

What the day count does not decide

Meeting the test does not automatically make you a US tax resident. The closer-connection exception and tax treaty positions can change the outcome. The day count also says nothing about immigration status: how long you may stay under a visitor visa or entry permission is a separate question, answered by your admission record and not by the tax-day count.

The same logic applies to other countries’ tests. The UK day counter applies the Statutory Residence Test’s automatic indicators, and the Schengen 90/180 rule is an immigration limit, not a tax rule. They use different counting methods, so do not reuse one count for another.