How countries count
“183 days” sounds simple, but countries differ on two things: which period they look at, and what counts as a day.
| Country | Period | A day counts if |
|---|---|---|
| United States | 3-year weighted formula (substantial presence test) | You were there at any time that day |
| United Kingdom | Tax year, 6 April to 5 April (UK counter) | You were there at midnight |
| Spain | Calendar year, more than 183 days | You were in Spain. Short absences still count unless you prove tax residence elsewhere |
| Portugal | Any 12 months starting or ending in the year, more than 183 days | Any full or part day that includes an overnight stay |
| New York State | 184 days or more in the tax year, with a permanent place of abode there | You were there for any part of the day |
For Portugal, pick “At midnight” as the closest match. Days are only one part of residency. Home, work, family and tax treaties matter too, so check with a tax adviser before you rely on a number.
Questions
What is the 183-day rule?
Many countries treat spending more than 183 days there in a year as one sign of tax residency. The details differ: which 12 months count, and whether part of a day or only a night there counts. Days are rarely the only test.
Does a travel day count as a day?
It depends on the country. In the US, any part of a day counts. In the UK, a day counts if you are there at midnight. In Portugal, a day counts if it includes an overnight stay.
Calendar year or any 12 months?
Spain uses the calendar year. The UK uses its tax year, 6 April to 5 April. Portugal looks at any 12-month period starting or ending in the year. Pick the window that matches your country.
Does this tell me if I am tax resident?
No. It counts days only. Residency also depends on your home, work, family and tax treaties. Talk to a tax adviser.
Sources
- IRS: Substantial presence test (any part of a day)
- legislation.gov.uk: Finance Act 2013, Schedule 45, paragraph 22 (midnight rule)
- GOV.UK: Tax on foreign income, residence (UK tax year)
- BOE: Ley 35/2006, artículo 9 (Spain, more than 183 days in the calendar year)
- Portal das Finanças: CIRS, artigo 16 (Portugal, any 12 months; overnight days)
- New York State: nonresident FAQs (184 days, any part of a day)
Not legal or tax advice.