A posting is not possible if one posted employee is replaced by another posted employee.
In the case of cross-border employment of workers, it must always be clarified which social security system applies. Within the EU, employees can only be subject to the law of a single Member State. This is usually the law of the country in which the employment is carried out.
However, in case of a posting the usual place of work does not change despite the activity abroad. The posted employees continue to be subject to the social security obligation of their home country. The maximum duration of a posting is 24 months. Furthermore, several employees may not replace each other - this is referred to as a "prohibition of replacement ".
Until now, it was the general view that the prohibition of replacement only applied to employees of the same employer. Thus, an enterprise could not use successively different employees abroad for the completion of the same activities.
The European Court of Justice (ECJ) has now ruled that it is not the specific employer that is important in the context of the prohibition of replacement. Decisive is alone whether several posted employees "replace" each other in their domestic position, i.e. carry out the same activities one after the other. The respective employers of the posted employees may even come from different member states.
In such cases, all employees concerned are subject to the regulations of the social security system at their place of work. If this is not observed, there is a risk that the foreign employer will commit social security fraud, which will be punished with considerable penalties.
Source: ECJ, decision of 06.09.2018, Ref. C-527/16