Someone sent from Dublin to Munich for a three month project will usually remain in the Irish social insurance system throughout. That is the correct answer under European coordination rules, and it is not obvious to a German labour inspector standing on a site asking why no German contributions are being paid.
The A1 certificate exists to answer that question in one document. It states which member state's social security legislation applies to a named individual for a named period, and it is binding on the authorities of every other member state.
What it covers and what it does not
- It covers social security only. Pension, health, unemployment, accident insurance and family benefits. It says nothing about income tax, which is governed separately by the relevant double taxation treaty.
- It is not a work permit. Immigration status, posting declarations and sector specific registrations are separate obligations.
- It applies within the EU, EEA and Switzerland. Outside that area, bilateral social security agreements perform the same function, usually with a different form and a slower process.
- It is issued by the home country. The institution in the country whose legislation applies issues it, on application by the employer or the self-employed person.
When you need one
The requirement is broader than most people assume. It is not limited to long postings.
The one day business trip case surprises people, and enforcement varies considerably. Austria, France and Belgium have been the most active at checking, particularly in construction, transport and events. Penalties fall on the employer but the practical disruption falls on the traveller.
The two bases for issuing one
An A1 is issued under one of two rules and it matters which.
- Posting. An employee sent to work in another state for a limited period remains insured at home, provided the posting does not exceed twenty four months and the person is not replacing someone whose posting has just ended. This is the standard project case.
- Multi-state activity. Someone habitually working in two or more states is insured in their country of residence if they perform a substantial part of their activity there, generally taken as at least a quarter of working time or pay. If not, they are insured where the employer has its registered office. This is the rule that catches hybrid and remote arrangements.
The second basis is now the more common one, and it produces results that are frequently the opposite of what the employer assumed. Someone living in Spain and working for a German company two days a week from Spain and three days in Germany will usually be insured in Spain, not Germany, because the Spanish share exceeds the substantial activity threshold.
Why it is worth having even when nobody asks
Without an A1, the host country is entitled to treat the work as subject to its own social security system and to assess contributions accordingly. The home country will not necessarily refund what was paid there, and recovering the position afterwards is slow.
For the individual, the consequences are less dramatic but still real. Contribution records feed pension entitlement, and periods recorded in the wrong country create gaps that only surface at retirement. Healthcare entitlement while abroad also depends on the correct state being identified.
How to get one
The employer applies to the home country institution: HMRC in the United Kingdom under the bilateral arrangement, the Deutsche Rentenversicherung in Germany, the URSSAF in France, the Sociale Verzekeringsbank in the Netherlands. Most now operate online portals and issue within days for straightforward postings.
If you are travelling for work regularly and have never seen one, ask. It is an employer obligation, it costs nothing, and the answer will tell you whether anyone has considered the question at all.
Related: no state tax states