Working in several EU countries: which social security applies
Short answer: Only one country's social security applies. For employees it is usually the country of residence if a substantial part of work is there; the A1 certificate proves it.
If you work or run a business in more than one EU or EFTA country at the same time, only one country's social security system applies to you. That decides where contributions are paid and which country covers your health care. This guide follows the Powroty page "Economic activity in several countries and social insurance", published on 10 June 2026 and stating the law as of 8 June 2026. We read it on 19 October 2026. It is a summary of EU coordination rules, not an individual ruling.
Employees working in several countries
According to the page, the EU coordination rules work like this for an employee:
- If you work for one employer, the law of your country of residence applies, as long as you do a substantial part of the work there.
- If that condition is not met and you have one employer, the employer's seat decides.
- With two or more employers whose seats are in one country, that country's law applies.
- With employers in two countries, one of which is your country of residence, the law of the other country applies, not that of your residence.
- With at least two employers in two different countries other than your country of residence, your country of residence decides.
If these rules lead to Polish law, the page says a foreign employer must pay contributions into the Polish system. The foreign employer may also authorise the employee to pay them on its behalf.
* Photos: the border bridge in Słubice (cover and body), CC0, via Wikimedia Commons, used as illustrations only.
Self-employed people in several countries
For self-employed people the page gives two rules. You are subject to the law of your country of residence if you carry out a substantial part of your activity there. If you do not live in the country where you do most of the activity, the law of the country where your centre of interest lies applies. The rules apply whether the business is registered in one country but works in several, or registered in different EU/EFTA countries.
The main activity is judged by where it is usually carried out, its usual character or duration, the number of services provided and the intention shown by all the circumstances.
The A1 certificate
The page stresses that you should have an A1 certificate. It states which country's social security law you are subject to, and holding it means you do not have to pay contributions in another member state. It also ties into health care. Treatment in the country where you work is billed to the state that issued the A1, on the basis of the EKUZ card, which in Poland is issued by the NFZ on the basis of the A1. The EKUZ card expires on the same date as the A1.
Other countries
For work in Poland and a non-EU country that has a bilateral social security agreement with Poland, the agreement applies. For work in the United Kingdom after 31 December 2020, the rules are similar, but ZUS confirms the A1 on the basis of the EU-UK Trade and Cooperation Agreement protocol on social security coordination. For work in Poland and a country with no agreement, Polish insurance applies under the general rules, according to the page.
What the sources do not say
The page does not define "substantial part" in percent. It does not say how to apply for an A1 at ZUS, how long it takes, or what forms to use. It does not cover tax, only social insurance. Contact ZUS or the social security institution of the other country before you start, and keep your A1 with you when you work abroad.
Frequently asked questions
Which country's rules apply if I live in Poland and work for one foreign employer?
According to the page, Polish law applies if you do a substantial part of the work in Poland. Otherwise the employer's seat decides.
What does an A1 certificate do?
It states which country's social security law applies to you, and means you pay contributions only there.
Does the same rule apply to non-EU countries?
Only for countries with a bilateral agreement with Poland, where the agreement applies. For the UK after 2020, the EU-UK protocol is the basis.
