EU Social Security Coordination is the framework established by Regulation (EC) No 883/2004 and its implementing Regulation (EC) No 987/2009. It does not harmonise national social-security systems but instead sets rules to determine which single member state's legislation applies to an individual at any given time. This single-state principle protects workers from double contributions while preserving each country's right to design its own benefit system.
The coordinating rules cover sickness, maternity, old-age pensions, work accidents, unemployment, family benefits, and pre-retirement benefits. Overarching principles include equal treatment, aggregation of periods completed in different member states, and exportability of certain benefits. The primary rule is that workers pay contributions in the country where they work; exceptions apply to postings (Article 12), multi-state workers (Article 13), and civil servants.
The framework applies across the 27 EU member states plus Iceland, Liechtenstein, Norway, and Switzerland under separate agreements. Since Brexit, a specific UK-EU agreement replicates comparable coordination for workers moving between the UK and EU member states, though its scope is narrower than the pre-exit arrangements.