There are three different situations:
1. The home and host country both belong to the EU (and Switzerland, Liechtenstein and Norway). In these countries, the EU a treaty on social security is applicable. This treaty determines which system of social security in which case is appropriate and consequently where contributions will have to be paid. Normally, the home country system can be maintained in case the assignment does not last longer than 24 months (which can be extended to 60 months); the employee is not replacing a former seconded employee, and the employee was part of the system of social security in the home country for at least one month. In such cases, the employer can file an application to the social security authorities for the so-called A1 statement. Please, note that under this agreement, it is not possible to maintain the home country system of social security for accompanying family members! It neither applies to the costs for medical expenses! Contributions and premiums will have to be paid in the home country.
2. The home and host country have agreed on a bi-lateral agreement on social security. It works the same as the EU method. However, every bi-lateral treaty has its own articles on applicable legislation, accompanying family members, duration and application procedures. The approval that the home system remains applicable is laid down in a Certificate of Coverage. Contributions and premiums will have to be paid in the home country.
3. The home and host country do not belong to the EU (and Switzerland, Liechtenstein and Norway) and do not have a bi-lateral agreement. In such cases, it might be possible to enter home country voluntary social security insurances. It usually offers a comparable home country level of social security. Premiums for these insurances will have to be paid in the home country, but it does not touch the obligation also to pay contributions to social security in the home country. It leads to double premiums and higher costs.
