Tax residency rules by country, explained

Spend 183 days or more in most countries during their tax year and you are generally resident there. The number is broadly shared; almost everything around it is not.

The 183 days is the same — the window isn't

• United Kingdom: 6 April to 5 April.
• Australia: 1 July to 30 June.
• Ireland, most of Europe, and the US: the calendar year.

The same trip can fall on either side of a fiscal boundary depending on where you are. A run of days that looks harmless against a calendar year can tip you over against an April-to-April one. What is the 183-day rule covers the baseline; the OECD's tax-residency portal links each jurisdiction's own definition.

Some countries look past the day count

A flat day count is the easy case. Several countries treat you as resident regardless of days if your life is centred there:

• Centre of vital interests: France, Germany, Spain and others weigh where your home, family and main economic ties sit.
• The UK narrows the 183 threshold through the Statutory Residence Test and its ties.
• The US taxes citizens worldwide and applies the weighted substantial presence test rather than a simple 183 — the free calculator shows that arithmetic worked through.

So "by country" really means three moving parts at once: the threshold, the tax year, and whatever ties test sits on top.

You can be resident in two countries

Because every country runs its own rules, the same set of days can make you resident in more than one place at the same time. Double-tax treaties exist to break those ties, but they only help once you know you have triggered residency somewhere you did not intend to. The first job is seeing the lines as you approach them.

How Flags Tax helps

Flags Tax rebuilds your country days from photo metadata and manual confirmation and watches each country's threshold and tax year separately, so a line building in a country you were not watching is flagged for review. For the mechanics of the record itself, see how to track tax residency days.

Flags is an early-warning tool, not tax advice. It does not model tax treaties or every jurisdiction-specific ties test — confirm your position with a qualified adviser.