183-Day Rule

The most common threshold used to determine tax residency: spending 183 or more days in a jurisdiction during a tax year typically triggers resident tax status on worldwide income (in worldwide-taxation countries) or on locally sourced income. Implementation varies: some countries count any partial day of presence, others use a rolling 12-month window instead of the calendar year, and many overlay additional tests such as 'centre of vital interests', habitual abode, or the 90-day UK tie test. The Schengen 90/180 rule is distinct — it controls how long non-residents may visit, not when they become tax resident. Day-counting is increasingly enforced via electronic border records; nomads and frequent travellers should document entries and exits carefully.