183-Day Tax Residency Calculator (incl. US Substantial Presence Test)

How it works

simple: days present in the tax year ≥ 183 → resident · US SPT: days this year + ⅓ × last year + ⅙ × year before ≥ 183, with ≥ 31 days this year

Most tax systems make physical presence the first test of residency, and the half-year mark — 183 days — is the most common line, though how days are counted differs: arrival and departure days, transit, and midnights all get different treatment from one country to the next. The United States smooths the test over three years so that someone spending four months every year cannot avoid residency forever: this year's days count in full, last year's at a third and the year before at a sixth. Because residency brings worldwide taxation, frequent travellers track the count against the specific tax year, which in the UK, Australia and India does not start in January, and plan the remaining days accordingly.

Worked example

Stays of 10 January–5 March (55 days), 20 April–31 July (103 days) and 1–14 September (14 days) in a January-to-December tax year total 172 days — 11 short of 183, so ten more days would still be safe. Under the US Substantial Presence Test with 120 days last year and 90 the year before, the weighted total is 172 + 40 + 15 = 227, which meets the test.

Frequently asked questions