The Court of Justice of the European Union (CJEU) on 11 December 2025 ruled that, when assessing whether an employee performs a “substantial part” of their activities in their member state of residence, all of that employee's activities must be taken into account -- including activities performed in third countries outside the EEA and Switzerland.
The case -- GKV-Spitzenverband (Case C-743/23) -- involved a German resident employed by a Swiss company who worked across multiple states over a five-year-period. More specifically, the employee worked partly:
The CJEU did not agree with that position and ruled that all working time must be considered when determining whether the 25% threshold is met, including time spent in third countries, provided the work is similar and performed under the same employment contract.
In the case at hand, only about 16% of the employee’s total working time was spent in Germany; therefore, the court concluded that the social security scheme of Switzerland -- the employer’s state -- was applicable.
The court based its decision on Article 13(1) of Regulation 883/2004 (multistate employment) and Article 14(8) of Regulation 987/2009, emphasising that the assessment requires an overall global calculation of total working time, not one limited to EU/EEA/Swiss activities.
Under EU Regulation 883/2004 on the coordination of social security systems in the EEA and Switzerland, together with Implementing EU Regulation 987/2009, an employee who works simultaneously in two or more member states will be subject to the social security legislation of their member state of residence if they perform “a substantial part” -- at least 25% -- of their working time there and/or receive remuneration from that member state. If that threshold is not met, the legislation of the state of employment (that is, the employer’s state) applies.
Prior to the CJEU ruling in this case, it was generally assumed that only working time/remuneration within the EEA/Switzerland should be taken into account when determining the 25% threshold. The court’s decision now clarifies that time spent working in third countries must also be included, provided the work there is similar and performed under the same employment contract.
The CJEU’s decision applies only to situations in which an employee works under one employment contract for one employer and performs similar activities in the various countries involved. The scope of the decision cannot be extended to situations whereby employees have multiple contracts and/or employers.
The CJEU’s ruling is relevant only for determining the applicable social security legislation among EEA member states and Switzerland. Consequently, no rights or obligations are created for work performed in third countries. The ruling also does not prevent those third countries from applying their own national legislation and/or bilateral agreements that may be in place.
The A1 declaration remains an essential document for employees working simultaneously in several member states. The percentage of employment spent in third countries should be disclosed in the A1 application when relevant. It is important to reassess the A1 declarations where necessary.
For payroll administration purposes, reassessing employees’ situations and social security positions may result in necessary adjustments of monthly payroll processing.
Employers with employees working simultaneously in multiple member states are strongly advised to review employees’ working time to ensure the correct social security application and continued compliance.
If you have any questions regarding your employees’ social security position, please contact your regular BDO contact or the author of this article.
Lien Maerevoet
BDO in Belgium
Summary of the Case
The case -- GKV-Spitzenverband (Case C-743/23) -- involved a German resident employed by a Swiss company who worked across multiple states over a five-year-period. More specifically, the employee worked partly:
- In Switzerland;
- Remotely from Germany; and
- In other countries outside the EU/EEA/Switzerland (third countries).
The CJEU did not agree with that position and ruled that all working time must be considered when determining whether the 25% threshold is met, including time spent in third countries, provided the work is similar and performed under the same employment contract.
In the case at hand, only about 16% of the employee’s total working time was spent in Germany; therefore, the court concluded that the social security scheme of Switzerland -- the employer’s state -- was applicable.
The court based its decision on Article 13(1) of Regulation 883/2004 (multistate employment) and Article 14(8) of Regulation 987/2009, emphasising that the assessment requires an overall global calculation of total working time, not one limited to EU/EEA/Swiss activities.
Legal Framework
Under EU Regulation 883/2004 on the coordination of social security systems in the EEA and Switzerland, together with Implementing EU Regulation 987/2009, an employee who works simultaneously in two or more member states will be subject to the social security legislation of their member state of residence if they perform “a substantial part” -- at least 25% -- of their working time there and/or receive remuneration from that member state. If that threshold is not met, the legislation of the state of employment (that is, the employer’s state) applies.Prior to the CJEU ruling in this case, it was generally assumed that only working time/remuneration within the EEA/Switzerland should be taken into account when determining the 25% threshold. The court’s decision now clarifies that time spent working in third countries must also be included, provided the work there is similar and performed under the same employment contract.
What Does the Ruling Mean in Practice?
The CJEU’s decision applies only to situations in which an employee works under one employment contract for one employer and performs similar activities in the various countries involved. The scope of the decision cannot be extended to situations whereby employees have multiple contracts and/or employers.The CJEU’s ruling is relevant only for determining the applicable social security legislation among EEA member states and Switzerland. Consequently, no rights or obligations are created for work performed in third countries. The ruling also does not prevent those third countries from applying their own national legislation and/or bilateral agreements that may be in place.
The A1 declaration remains an essential document for employees working simultaneously in several member states. The percentage of employment spent in third countries should be disclosed in the A1 application when relevant. It is important to reassess the A1 declarations where necessary.
For payroll administration purposes, reassessing employees’ situations and social security positions may result in necessary adjustments of monthly payroll processing.
Employers with employees working simultaneously in multiple member states are strongly advised to review employees’ working time to ensure the correct social security application and continued compliance.
If you have any questions regarding your employees’ social security position, please contact your regular BDO contact or the author of this article.
Lien Maerevoet
BDO in Belgium