When it comes to social security, the basic principle shall be in force, namely, that you may only be subject to social security in one country at a time. Thus, even if a business is run in several Member States at the same time, the insurance shall be provided by only one country and it is necessary to pay all social security contributions therein.
In terms of local jurisdiction, it should be:
- your country of residence - if you do a significant part of your work therein
- a country where the centre of interest (centre of interests) for your business is located - if you do not live in a country where you do a significant amount of work.
In order to determine whether a significant part of the business is performed in a given country, either, turnover, working time, number of services rendered, or income shall be taken into account. The document stating where contributions should be paid shall be te A1 form. The A1 template is identical throughout the European Union. Based thereon, contributions shall be paid in a given EU country and an exemption from the obligation to pay these contributions in another country is also obtained.
If you are insured in Poland (according to the principles applicable to Polish entrepreneurs), you shall deal with all matters related to insurance at the Social Insurance Institution (ZUS).