The 183-day rule for tax residency

Last updated October 26, 2026

You often hear that spending 183 days in a country makes you tax resident there. That is a useful rule of thumb, but there is no single worldwide 183-day rule. Each country decides how to count days, which year to use, and what else matters. Here is how the two best-known tests work, the US substantial presence test and the UK statutory residence test, and how to keep track. Stamp90 can count both for you alongside your Schengen days.

This is general information to help you count days. It is not tax advice. Tax residency can depend on far more than days, so speak to a qualified adviser about your situation.

What the 183-day rule usually means

183 days is just over half a year. Many countries use it as one test of residence: if you spend 183 days or more there in a tax year, you are likely to be treated as tax resident. Two warnings apply everywhere:

• Fewer than 183 days does not make you non-resident. Many countries also look at your home, work, family and other ties, and you can be resident with far fewer days.
• The year is not always January to December. The UK tax year starts on April 6, Australia's on July 1, and New Zealand's and India's on April 1.

Tax treaties also mention 183 days, often for whether a short work assignment abroad is taxed there. That is a different question from residency, with its own counting rules.

United States: the substantial presence test

If you are not a US citizen or green card holder, the IRS uses the substantial presence test to decide whether you are a US resident for tax purposes. You meet it if you were physically present in the US on at least:

• 31 days during the current year, and
• 183 days during the 3-year period that includes the current year and the two years before, counting all the days in the current year, one-third of the days in the year before, and one-sixth of the days in the year before that.

Example. You spend 120 days in the US in each of 2024, 2025 and 2026. For 2026 the count is 120 + 40 (one-third of 120) + 20 (one-sixth of 120) = 180. That is below 183, so you do not meet the test for 2026. Four more days in 2026 would take you to 184.

The IRS treats you as present on any day you are physically in the US at any time during the day. Some days are not counted, including regular commuting days from Canada or Mexico, transit of less than 24 hours between two places outside the US, days as a crew member of a foreign vessel, days you cannot leave because of a medical condition that arose in the US, and days as an exempt individual such as certain students and teachers. A closer-connection exception may also apply.

US citizens are taxed by the US wherever they live, so this test is for non-citizens. In Stamp90, add the US substantial presence test in Settings: it shows your weighted total and how many more days you can spend this year before meeting the test. It does not model the exempt days or the closer-connection exception.

United Kingdom: the statutory residence test

The UK tax year runs from April 6 to April 5 the following year. Under HMRC's statutory residence test:

• You are automatically UK resident if you spend 183 or more days in the UK in the tax year.
• You are automatically non-resident if you spend fewer than 16 days in the UK, or fewer than 46 days if you were not UK resident in any of the 3 previous tax years. Other automatic tests look at full-time work.
• If neither applies, the sufficient ties test combines your day count with ties such as family, accommodation and work in the UK.

The day count works differently from the US. Under the Finance Act 2013, a day counts as a day spent in the UK if you are in the UK at the end of the day, that is, at midnight. There is an exception for passengers in transit who arrive one day and leave the next without doing anything substantially unrelated to their journey, and HMRC can disregard a limited number of days spent in the UK because of exceptional circumstances.

In Stamp90, add a 183-day rule for the United Kingdom in Settings and it uses the April 6 tax year automatically. Stamp90 counts your entry and exit days as full days, which is the cautious approach: your Stamp90 count can be a day or two higher than HMRC's midnight count, never lower.

Tracking your days well

• Log every trip with entry and exit dates, and keep boarding passes and booking emails as evidence.
• Use the right year for each country. A trip from March to May can fall into two UK tax years.
• Watch the countdown, not just the total. Knowing you have 20 days left before 183 is what lets you plan.
• If two countries could both treat you as resident, the tax treaty between them may have tie-breaker rules. That is a question for an adviser.

Spending time in Europe too? The Schengen 90/180 rule is a separate limit on your visits, and US and UK travellers have their own guides: US citizens and UK citizens.