The A1 certificate proves that a posted worker or self-employed person stays covered by their home country's social security while working in Portugal.
What it is?
The A1 certificate is a form used across the European Union and the European Economic Area (EEA, the EU plus Iceland, Liechtenstein and Norway). It confirms which country's social security system covers a worker or a self-employed person while they work temporarily in another EEA country, such as Portugal, instead of both countries claiming coverage at once.
What it is for?
Without the A1, a person working temporarily in Portugal could end up owing social security contributions in two countries at once, or facing confusion about which country actually covers them if an accident happens. The certificate settles this in advance and avoids double payment, giving both the worker and the client clarity from the start.
Who needs it?
Anyone posted to work in Portugal by an employer based in another EU or EEA country needs the A1 certificate. A self-employed person from another EU or EEA country, temporarily working in Portugal, also needs it to keep paying contributions at home instead of in Portugal.
Where to get it and how long is it valid?
The certificate is issued by the social security authority of the person's home country, before the work in Portugal starts. It is valid for the period stated on the certificate, which usually matches the expected length of the posting or the self-employed activity, and can sometimes be extended if the work continues.
What to watch out for
Sometimes no A1 certificate is available. In that case, two other outcomes are possible. Some countries outside the EU or EEA have a bilateral treaty with Portugal, and a Certificate of Coverage under that treaty can serve the same purpose. If neither an A1 nor such a treaty applies, Portuguese social security contributions become due from the very first day of work in Portugal.
No A1 does not automatically mean Portuguese social security applies - check first whether a bilateral treaty and its own Certificate of Coverage cover the situation instead.