Glossary
183-day tax residency rule
Common shorthand for the tax-residency tests that make an individual liable for income tax in a country once they spend more than 183 days there within a defined window. Implementation varies sharply: the US uses a three-year weighted Substantial Presence Test, the UK layers ties around the day count under its Statutory Residence Test, and most EU countries apply 183 days inside a calendar or rolling year.
The 183-day rule is the tax-residency test that makes someone liable for income tax after spending 183 days in a country.
For global payroll and mobility teams, the real question isn't whether the 183-day line exists. It's which version of the line the host country actually applies, how it counts the days, and Whichapp switch flips the moment the threshold lands.
The clean version of the rule lives in the OECD Model Tax Convention at Article 15(2). It says short-term assignees stay taxable at home if they spend fewer than 183 days in the host country, the employer is not host-resident, and the cost isn't borne by a host-country permanent establishment.
Domestic law is messier. The US runs a three-year weighted formula in its Substantial Presence Test, and the UK layers 16, 46, 91, and 183-day thresholds under the Statutory Residence Test.
Germany triggers full residence at six months of physical presence under §9 of the Abgabenordnung. France can claim residence on centre-of-economic-interest grounds long before the day count gets to 183.
Why the 183-day rule rarely means what people think
The phrase reads like a single global threshold. It isn't. The "183 days" line shows up in three legally distinct places, and conflating them is the most common mobility-tax mistake.
OECD treaty rule vs domestic law
The OECD's 183-day rule in Article 15(2) is a tiebreaker. It tells two countries which one taxes a short-term assignee when both could otherwise claim him. It does not, on its own, create tax residence in either country.
Domestic law is what creates residence. The UK, US, Germany, France, and Spain each have their own definition, and treaty relief only kicks in after the domestic test has already pulled the assignee into the local tax net.
The "more than" versus "183 or more" trap
Some countries count the threshold as "more than 183 days" (the UK and the OECD model). Others use "183 days or more" (Germany, France). One day either side moves the assignee from non-resident to resident.
Payroll providers default to the domestic definition; some buyers default to the treaty version. Where the contract is silent, the host country wins.
Rolling year, tax year, or calendar year?
The window matters as much as the count. Germany measures continuous presence over a rolling 12 months, while France uses the calendar year.
The UK runs the SRT against the 6 April to 5 April tax year. The OECD permits either a 12-month rolling window or a fiscal/calendar year, and the host country decides which.
Country-by-country: how each one actually counts the days
The 183-day line means different things in different jurisdictions. The table below sets out what to count, when to count it, and what the threshold actually triggers.
| Country | Test name | Day-count rule | Window | Statutory basis |
|---|---|---|---|---|
| United States | Substantial Presence Test | Weighted: full Y1 + 1/3 Y2 + 1/6 Y3, AND ≥31 days in Y1 | Three-year rolling | IRC §7701(b); IRS Pub 519 |
| United Kingdom | Statutory Residence Test | 183-day auto-resident; ties ladder from 16 days | UK tax year (6 Apr to 5 Apr) | Finance Act 2013 Sch 45; HMRC RDR3 |
| Germany | Gewöhnlicher Aufenthalt | More than 6 months continuous physical presence | Rolling 12 months | §9 Abgabenordnung |
| France | Foyer / 183-day / centre of interests | Three alternative tests; any one triggers residence | Calendar year | CGI Article 4 B; BOI-IR-CHAMP-10 |
| Spain | 183-day or economic-interest | 183 days inside calendar year; sporadic absences counted | Calendar year | LIRPF Article 9 |
| Switzerland | 30/90-day employment test | 30 days with gainful activity OR 90 days without | Continuous | DBG Art. 3 |
US: the Substantial Presence Test weighted formula
The IRS rule is the one most often miscounted. An assignee meets the SPT if they are physically present at least 31 days in the current year, and the sum of current-year days plus one third of the prior year plus one sixth of the year before that totals 183 or more. IRS Publication 519 sets out the mechanic in full.
Worked example: 130 days in 2026, 130 in 2025, 130 in 2024 gives 130 + 43 + 22 = 195. Resident under SPT despite never crossing 183 days in any single year.
Cut Year 1 to 120 and 2025 to 120 and the total drops to 120 + 40 + 20 = 180. Not resident.
UK: the Statutory Residence Test ladder
HMRC's RDR3 sets out the SRT. It runs three sequential tests: automatic overseas (under 16 days for leavers, under 46 for arrivers), automatic UK (183 or more days, or a UK home with no overseas home), and the sufficient-ties test in between.
The ties test counts family, accommodation, work, 90-day-prior, and country ties against the day count. An arriver with three ties becomes UK-resident at 46 days, not 183. Most short-term assignees underestimate this.
Germany, France, and the EU patchwork
Germany's §9 Abgabenordnung triggers full income-tax liability after roughly six months of continuous physical presence, with short interruptions disregarded. The German tax office takes a strict physical-day view; weekends spent in-country count. See the Germany country guide for the operational view.
France runs three alternative tests under Article 4 B of the Code Général des Impôts: habitual residence (foyer), 183 days in France, or centre of economic interests. Any one of the three creates residence, which means assignees with French-source income or a French family home can be resident before they ever hit day 183. The France country guide covers the URSSAF and impatriate-regime angle.
The payroll trigger: when host-country PAYE kicks in
The 183-day moment isn't only a tax-return event. It's a payroll switch. The host country's payroll system flips from non-resident withholding (or no withholding) to full resident PAYE, and the employer's social-charge obligation usually starts the same day.
| Payroll trigger | When it fires | Action required | Who owns it |
|---|---|---|---|
| Host PAYE registration | At assignment start if posting >183 days planned | Open local payroll or appoint EOR | Mobility / payroll |
| Day-count tracking | From day 1 of host activity | Calendar of presence; airport stamps as fallback | Assignee + HR |
| Treaty article 15(2) test | If assignment crosses 183 days | Confirm employer status and PE position | Tax adviser |
| Host social-security routing | At assignment start | Apply for A1 or certificate of coverage | Home payroll |
| Shadow payroll | When tax equalisation policy applies | Open home shadow record alongside host payroll | Mobility-tax provider |
Build the day-count log into the assignment workflow on day one. Retrofitting one in month four, after a tax-office query, is significantly harder than collecting boarding passes weekly.
The downstream cost lines compound. Once host residence triggers, tax equalisation usually applies, and the employer also needs a certificate of coverage to suppress double social security.
Where the 183-day rule meets permanent establishment risk
An assignee's day count is a personal-tax test. It can also trigger a corporate-tax problem if the activity creates a permanent establishment for the employer in the host country.
The OECD Article 5 link
OECD Model Tax Convention Article 5 defines permanent establishment by fixed place of business, agency, or services. The 183-day individual-residence line isn't the same as the PE test, but the two interact: an assignee who concludes contracts in-country or runs a sales function from a home office can create a dependent-agent PE long before they breach 183 days personally.
Once a PE exists, the OECD Article 15(2) relief that would otherwise keep the assignee out of host tax also falls away. The country can tax the employee under domestic law because the cost is borne by a host-country PE.
What buyers should map at assignment design
- Likely day count over the assignment window, including business-travel overflow.
- Whether the assignee will sign customer contracts in the host country.
- Whether the host EOR or branch will bear assignment cost via recharge.
- Whether the home payroll or host payroll runs the tax withholding.
- Whether global mobility policy treats short-term assignments as taxable.
Whichapp view
Most EOR providers price assignments off the headline base salary and assume the buyer has confirmed the residence position. They have not. Run the host-country day-count and ties test before signing the assignment letter, and budget for the moment local PAYE switches on rather than the moment day 184 arrives.
For scenario modelling across countries, the employer cost burden calculator covers the per-country loading once host residence triggers. See our Deel review for how the assignment workflow tracks the 183-day moment in the host payroll, and the best global payroll providers shortlist for providers that integrate day-count tracking into the mobility service.
See our ranked shortlist of providers, scored across pricing transparency, country coverage, and contract flexibility. Updated for 2026.
View the shortlist →183-day rule FAQs
Is the 183-day rule the same in every country?
No. The OECD treaty version is a tiebreaker that uses any rolling 12-month or fiscal year and a strict "more than 183 days" count. Domestic law diverges.
The US runs a three-year weighted formula, the UK uses a ties-based ladder starting at 16 days, Germany applies a six-month physical-presence test, and France can claim residence on centre-of-economic-interest grounds before the day count is reached. Treating it as one global rule is the most common mobility-tax mistake.
Do weekends and travel days count toward the 183 days?
Usually yes. Most countries count any day on which the individual is physically present at midnight, including weekends, holidays, and partial travel days.
The UK SRT counts a day if the person is in the UK at the end of it. Germany counts each day of physical presence with short absences ignored. The US SPT counts any day of presence other than days in transit between two non-US points.
Does staying under 183 days mean no host-country tax?
Not on its own. Treaty relief under OECD Article 15(2) requires three conditions: under 183 days, employer not resident in the host country, and remuneration not borne by a host-country permanent establishment.
If any one fails, the host country can tax the assignee even at day 100. Countries like France can also claim residence on family or economic ties before the day count matters.
How does the 183-day rule affect payroll?
Once the threshold is met, the host country's payroll engine switches on. The employer registers for local PAYE or appoints an EOR, withholds host-country income tax, and remits employer-side social charges if no certificate of coverage applies.
For tax-equalised assignments, a shadow home payroll usually runs alongside the host record. The trigger date is often locked in the assignment letter, not the actual day-count moment.
Can a certificate of coverage block the 183-day tax trigger?
No. A certificate of coverage blocks host-country social security, not host-country income tax. The two run on separate rules.
An assignee with a valid A1 still becomes liable for host-country income tax once the residence threshold is met, even though their social-security contributions continue at home. Mobility policies that conflate the two routinely undercost long-term assignments by 15 to 25 per cent.