CJEU clarifies social security rules: Work in third countries counts in “substantial part” assessment

On December 11, 2025, in case C-743/23 Moguntia Food Group / GKV-Spitzenverband, the European Court of Justice (“CJEU”) ruled on a previously unresolved issue concerning which social security legislation applies to global work. The question was whether work performed in third countries should be included when determining if a worker performs a "substantial part" of their employment in their Member State of residence, as outlined in Article 13(1) of Regulation (EC) No 883/2004 of the European Parliament and of the Council on the coordination of social security systems, in conjunction with Article 14(8) of Regulation (EC) No 987/2008 of the European Parliament and of the Council, which establishes the procedures for implementing Regulation No 883/2004.

The case concerned a worker resident in Germany, employed by a Swiss company. The work was performed partly in Switzerland, partly as homework in Germany, as well as in third countries. In 2015, the employee informed the German authorities that he performed less than 25% of his work in Germany and that he was enrolled in the mandatory Swiss health insurance. 

However, the German Federal Association of Statutory Health Insurance Funds (GKV-Spitzenverband) determined that the worker performed a significant portion of his employment in his state of residence because the authorities only considered work performed in the member states, including Germany and Switzerland. Given this, German social security legislation was deemed applicable. The employee appealed the decision, but the appeal was rejected. The employee brought the case before the Sozialgericht (social court in Germany) for review. On August 4, 2022, the Sozialgericht overturned the previous decision, ruling that the employee had not performed a substantial part of his work in the Member State of residence. Only 10.5 working days per quarter, equivalent to around 16% of his total work hours, were completed in Germany. The GKV-Spitzenverband appealed the judgment, and the question of interpreting the concept of "substantial part of employment" and including work performed in third countries was referred to the CJEU. 

The decision of the CJEU 

The CJEU ruled that Articles 13(1) and 14(8), when read together, must be interpreted to mean that when determining whether a person employed in several Member States pursues a substantial part of their activity in their Member State of residence, account must be taken not only of work performed in the Member States, but also of work performed in third countries. Thus, the assessment must be based on the worker's overall professional activity. 

Since the worker in question performed only approximately 16% of his total work hours in his residence country, the Court held that he did not carry out a "substantial part" of his employment there. Therefore, he was not covered by the Member State of residence’s social security legislation.

Littler notes

The judgment states that the assessment of whether a worker performs a "substantial part" of their work in the Member State of residence must consider the worker's total professional activity, including work performed in third countries. This implies that work performed globally can have a decisive impact on applicable social security legislation and may render the legislation of the Member State of residence inapplicable.