Tax residency explained for international employers

Tax residency determines where an individual pays income tax and, in some cases, where your company has tax obligations. For international employers hiring across borders, understanding how tax residency works is not optional. Get it wrong and you face double taxation, penalties, or an unexpected permanent establishment that triggers corporate tax obligations in a country where you never intended to have a presence.

This guide covers what you need to know as an employer. It is not a substitute for tax advice on your specific situation, but it gives you the framework to ask the right questions and avoid the most common mistakes.

Tax residency is the basis on which a country claims the right to tax an individual’s income. Most countries tax their residents on their worldwide income and tax non-residents only on income sourced within their borders.

The rules for determining tax residency vary by country, but they generally fall into a few categories.

Physical presence tests. Many countries use a day-count rule. If an individual is physically present in the country for more than a set number of days in a tax year (often 183 days), they become tax resident. The US, UK, and most EU countries use some version of this, though the details differ.

Domicile and centre of vital interests. Some countries look beyond physical presence. Where is the person’s permanent home? Where is their family? Where are their economic and social ties strongest? The UK’s domicile rules and France’s “centre of vital interests” test are examples.

Citizenship-based taxation. The US and Eritrea are the only countries that tax based on citizenship regardless of where the person lives. US citizens and green card holders owe US tax on worldwide income even if they have not set foot in the country for years.

Registration-based rules. In Scandinavian countries like Denmark and Sweden, registering with the national population register can trigger tax residency even before you meet a day-count threshold.

For employers, the critical point is this. Where your employee is tax resident affects where you need to withhold tax, what social security obligations apply, and potentially whether your company itself has a taxable presence in that country.

Tax residency is primarily an individual obligation. But it has direct consequences for employers in three areas.

No two countries apply exactly the same rules. Here is a practical overview of how some major markets approach tax residency.

United Kingdom. Uses the Statutory Residence Test (SRT), introduced in 2013. It is based on a combination of day counts, ties to the UK (family, accommodation, work, and social ties), and whether the individual was UK resident in previous years. Someone can be non-resident despite spending up to 182 days in the UK if they have few ties. Conversely, someone with strong ties can become resident with fewer than 90 days of presence.

Germany. Tax residency is triggered by having a domicile (Wohnsitz) or habitual abode (gewöhnlicher Aufenthalt) in Germany. A habitual abode is generally established after six consecutive months of physical presence. Germany also looks at whether you maintain a dwelling that is available to you, even if you do not live in it full-time.

France. Uses a four-part test based on habitual abode, principal place of residence, centre of economic interests, and professional activity. Meeting any one of these can make you French tax resident. France is particularly aggressive about taxing individuals with economic interests in the country, even if their physical presence is limited.

Denmark. Tax residency applies from the date you acquire a permanent home (bolig) in Denmark. There is also a six-month rule for those without a permanent home but with extended physical presence. For international employers hiring in Denmark, understanding the interaction between tax residency and the 183-day rule under double tax treaties is important. See our guide to hiring in Denmark through an EOR for more on the Danish employment framework.

United States. Taxes based on both residency and citizenship. Non-US citizens become tax resident if they hold a green card or meet the “substantial presence test” (183 days using a weighted three-year formula). US citizens owe tax regardless of residency.

United Arab Emirates. Introduced a personal income tax residency framework in 2023, though there is currently no personal income tax. The residency rules are relevant for determining treaty access and could become important if the tax regime evolves.

Employees move. They relocate for personal reasons, they follow a partner, they spend extended time working from a country that was supposed to be temporary. When this happens, the employer needs to respond.

Mid-year relocations. Most countries allow split-year treatment, where the employee is resident in the old country for part of the year and the new country for the rest. But the rules for when the split applies, and how income is allocated, differ. Some countries tax the full year’s income if the employee is resident at any point during the year.

Remote work from another country. If your employee has been working from Portugal for six months because they “prefer the weather,” their tax residency may have shifted. This is increasingly common and increasingly problematic. Many countries now actively enforce residency rules against remote workers who have not registered locally.

Assignment vs permanent relocation. Short-term assignments (typically under 183 days in a 12-month period) are usually covered by the employment article of the relevant double tax treaty, keeping the employee taxable only in their home country. But if the assignment extends, or if the employer has a PE in the host country, this exemption can fall away.

The employer’s obligations change with the employee’s residency. This is why tracking where your people actually work, not just where they are supposed to work, is essential.

Know where your employees are. This sounds basic, but it is the most common failure point. Implement a system for tracking employee locations, especially for remote and hybrid teams. “Work from anywhere” policies need boundaries.

Understand the trigger points. For each country where you have employees or where employees spend time, know the residency thresholds and PE risks. Build these into your mobility policies.

Use double tax treaties. Before an employee relocates or takes an extended assignment, check whether a treaty exists between the home and host countries. Understand the tie-breaker rules and the exemptions available for short-term assignments.

Get certificates of coverage. For social security, many countries have bilateral or multilateral agreements (like the EU’s A1 certificate system) that prevent double contributions. Your employee may need a certificate of coverage from their home country to remain in the home social security system during a temporary assignment.

Plan payroll splits. If an employee is tax resident or has tax obligations in two countries, you may need to run split payroll or at least coordinate withholding across jurisdictions. This is complex but manageable with the right support.

Consider an Employer of Record. An Employer of Record takes on the legal employment, payroll, and tax compliance obligations in countries where you do not have an entity. This is one of the most practical ways to manage tax residency compliance when you have employees scattered across borders. The EOR ensures that withholding, contributions, and filings are handled correctly in each country according to local rules.