Last updated: 16 September 2026
The country a person habitually works in normally governs the employment relationship. Travelling to sell in other countries does not move it by itself. A salesperson who lives and works from one EU country, and visits customers in four others, is usually employed under the law of the country they work from.
Three questions get blurred here, and they have three separate answers. Which country's employment law governs the contract. Where income tax is due. Which social security system the person stays in. Each one is decided by a different rule, evidenced by a different document and settled by a different authority. The first of them, employment law, comes from the Rome I Regulation, Regulation (EC) No 593/2008.
This page takes the three in turn and keeps them apart. It does not cover payroll registration or withholding in each country visited. That sits on a separate page, linked below.
Which country's employment law applies?
The law of the country where the employee habitually works applies. Habitually means the place they normally work in or work out of, week in and week out. That is the test in the Rome I Regulation, which the EU uses to decide which country's law governs a contract. For employment it looks at the country in or from which the person carries out their work, and not at where the customers sit.
Rome I also says the habitual place of work does not change when someone is sent to another country for a short period. A week of meetings in Warsaw does not put the contract under Polish law. You can name a governing law in the contract. That choice cannot take away the protection the employee would have had in their base country. So the base country still sets the floor on notice, holiday and dismissal rights. The rule is set out in Article 8 of Rome I.
So the sales territory is not what decides the contract. Where the person lives and works from is. The harder cases are people with no clear base at all, or a base that moves during the year. Those are worth talking through one at a time.
Where is income tax due?
Income tax is normally due in the country where the work is physically done. On top of that, the country the person lives in will usually tax them on all of their income, then give relief for tax already paid elsewhere. There are no EU-wide income tax rules for people who live or work outside their home country, as Your Europe sets out. National law and the tax treaty between the two countries decide it.
That matters for someone selling across a region. Days worked in another country can in principle be taxable there. Most treaties then hand the taxing right back to the home country if a set of conditions is met. Those conditions cover the days spent in the other country, who pays the salary, and whether the employer has a base there. The limit sits in the treaty itself, so read the treaty for the two countries in front of you.
Registration, withholding and the mechanics of payroll in more than one country are a subject of their own. Our guide to EU remote employee tax compliance covers that ground.
Which social security system applies?
One system at a time. The EU coordination rules, Regulation (EC) No 883/2004, exist so that a person pays into a single member state's system even when their work crosses several borders. You do not split contributions between the countries visited, and the person does not lose cover by getting on a plane.
Where someone regularly works in more than one country, the starting point is the country they live in, and it is that country's social security institution that decides. Your Europe says a person working in various countries at the same time should first contact the institution in their country of residence. The answer depends on how much of the work happens there and on where the employer sits. It is decided case by case, and no employer can settle it alone.
The document that records the answer is the A1. It states which country's legislation applies to the person, and it is what an inspector or a client abroad will ask to see. Our A1 certificate guide explains how it is applied for and how long it runs.
Which document proves each answer?
Each of the three questions has its own decider, its own paperwork and its own issuer. Mixing them up is how employers end up with a contract written for one country, tax advice written for another, and no social security cover recorded anywhere.
Employment law is evidenced by the contract itself, which you and the employee sign. Tax is evidenced by payroll records and, where a treaty is in play, by a certificate of tax residence from the tax office. Social security is evidenced by the A1. The table is a summary of the three, not a decision on any of them.
| Question | What decides it | What evidences it | Who issues that |
|---|---|---|---|
| Employment law | The country the person habitually works in or from, under Rome I | The employment contract | The employer and the employee |
| Income tax | Where the work is done, then the tax treaty between the countries | Payroll records and a certificate of tax residence | The tax office in the relevant country |
| Social security | The EU coordination rules, starting from the country of residence | The A1 | The social security institution in the country of residence |
What should you put in writing before the first trip?
Write down where the person is based, what the territory is, and roughly how much of their time is expected to be spent outside the base country. The base country drives the contract, the payroll and the A1 application, so it needs to be stated rather than assumed. If the base is the Netherlands, our Netherlands hiring guide covers what a Dutch contract has to contain.
Then agree what the role can and cannot do while abroad. Where a person regularly agrees terms and closes deals for the employer in another country, that country may treat the employer as having a taxable presence there, known as a permanent establishment. It turns on what the person actually does, not on their job title, so the limits are worth writing down early.
Keep a simple record of travel from the first month. Expenses, posted worker notifications and the A1 all rest on the same facts. They are far easier to produce as you go than to rebuild a year later. The right answer depends on your employee's situation, so work through yours with someone before the contract is signed.