OD FLASH | Social security affiliation in the case of multiple activities: consideration of activities carried out in non-EU countries

EUR-Lex – 62023CJ0743 – FR – EUR-Lex

In a judgment dated December 11, 2025, the CJEU clarified the interpretation of Article 13(1) of Regulation (EC) No. 883/2004, in conjunction with Article 14( §8, of Regulation (EC) No. 987/2009, relating to the determination of the social security legislation applicable to an employee working in several States, including Member States and third countries.

European regulations enshrine the principle of the uniqueness of the applicable legislation, according to which an employee may only be subject to one compulsory social security scheme at a time (Article 11 of Regulation (EC) No. 883/2004). Thus, when an employee works in several Member States, he or she may only be subject to a single social security scheme.

In accordance with Article 13 of Regulation (EC) No. 883/2004, an employee engaged in multiple activities is subject to the social security legislation of their State of residence if they carry out a substantial part of their activity there, and, failing that, to that of the State in which their employer is established, which makes the assessment of the substantial nature of the activity carried out in the State of residence decisive in determining the applicable legislation.

In this case, an employee domiciled in Germany and employed full-time by a company established in Switzerland carried out part of his professional activity remotely from Germany, as well as in person in Switzerland and, to a lesser extent, in several third countries.

The employee, who was affiliated to the Swiss social security system, contacted the German social security administration to determine the legislation applicable to his situation, with the latter opting for the application of German legislation. The German court then asked the CJEU whether the concept of “substantial part of the activity” in the State of residence should be assessed solely on the basis of activities carried out in the European Union or on the basis of all activities, including those outside the EU.

The Court ruled that the assessment must cover all of the worker’s salaried activities, including those carried out in third countries. In this case, the activity carried out in Germany represented only 16% of the overall activity: the employee could not therefore be considered to be carrying out a substantial part of his activity in his State of residence. The applicable social security legislation was therefore that of Switzerland, the employer’s country of establishment.

This ruling confirms a factual and comprehensive approach to international multiple activities and provides important clarification for determining the applicable legislation, particularly for situations involving activities outside the European Union.