New ECJ Ruling Redefines Social Security Coverage for Multi-State Workers 

The European Court of Justice (ECJ) has issued a landmark ruling that affects how social security obligations are assessed for employees working across multiple countries.

In its recent judgement in the GKV-Spitzenverband case (Case C-743/23), the ECJ clarified that all employment activities must be taken into account, including work performed in third countries outside European Economic Area (EEA) and Switzerland, when determining applicable social security legislation.

This blog outlines the main takeaways from the decision and how the ECJ ruling raises important questions for social security compliance in the European Union (EU).

What was Case C-743/23 About?

Case C-421/23 originated from a dispute concerning the social security liability of an employee who

• • • resided in Germany,
    • worked full-time for a Swiss company, and
    • performed work across multiple jurisdictions between 2015 and 2020.

The employee carried out his activities:

• • • partly in Switzerland,
    • partly from home in Germany, and
    • partly in non-EU countries.

The German Health Insurance Fund (GKV-Spitzenverband) determined that the Swiss employer had to pay German social security contributions on the employee’s remuneration. This decision was based on the employment activities performed in Germany and Switzerland, taking into account that the employee spent 50 percent of his working time in Germany, exceeding the so-called 25 percent threshold for “substantial activities” under the EU social security regulations.

The employee disagreed, arguing that all work, including work in non-EU countries, should be counted. When those activities were included, his work in Germany dropped to 16 percent, which would make Swiss social security applicable instead.

Overview of the ECJ Ruling in Case C-74323 

• • • All work must be counted to reflect the real situation of the employee. The concept of “activity” is not limited to work performed within EU Member States. It encompasses all employment activities, including those carried out in third countries, when assessing whether a “substantial part” of the activity is pursued in the Member State of residence.
    • Consistency with the principle of a single applicable social security legislation. Where no substantial part of the activity is pursued in the Member State of residence, the social security scheme of the Member State where the employer is established applies. This approach thereby preserves legal certainty and avoids gaps or overlaps in liability.

What the New ECJ Decision Means for Multi-State Workers?

The ECJ ruling represents a significant shift in the assessment of multi-state workers and may lead to changes in the social security liability of many cross-border employees.

The decision also raises several practical and compliance considerations. Employers may need to

• • • reassess existing mobility arrangements and working patterns, and
    • review documentation to ensure that the correct national social security scheme is applied.

How Does This Affect Current Coordination Agreements?

Uncertainty remains as to the impact of this ruling on existing coordination agreements. In particular, the Framework Agreement on cross-border teleworking, which does not take account of work performed in third countries, and it is unclear how the ruling will interact with that agreement.

The decision may also have implications for the EU-UK Trade and Cooperation Agreement, although its effect on multi-state workers between EU and the UK remains unclear.

Practical Impact on A1 Certificates and Compliance Strategy

From a practical perspective, it remains to be seen how Member States will implement this ruling. Open questions include:

• • • how authorities will adapt their application questionnaires,
    • how time spent outside the EEA and Switzerland will be monitored, and
    • how existing A1 certificates or renewal applications will be treated.

Finally, it remains unclear whether this interpretation will apply retroactively, and whether employers and authorities will be required to review previously determined applicable legislation.

Until further clarification is provided, employers with a mobile workforce should closely monitor developments and consider reviewing their current arrangements.

How Can Fragomen Help?

Fragomen Consulting Europe (FCE) can assist clients in managing their A1 certificate compliance program in line with the new case laws.

With a proactive compliance approach, the team helps ensure that social security, immigration, and posted worker obligations are considered early in the planning process.

Need To Know More?

For questions regarding A1 compliance, please contact the Fragomen Social Security team at [email protected]

This blog was published on 22 December 2025, and due to the circumstances, there are frequent changes. To keep up to date with all the latest updates on global immigration, please subscribe to our alerts and follow us on LinkedIn, Twitter, Facebook and Instagram.