Self-employed individuals in Belgium may exercise a main activity or a complimentary one.
If you are self-employed, you must join a social insurance fund and pay social security contributions.
To qualify as self-employed, you must be over 18 years old. Tradesmen; people exercising liberal professions (doctors, lawyers, architects, etc.); farmers and livestock breeders and company representatives are self-employed.
In order to become self-employed, you must:
You must join a social insurance fund either 6 months before starting your activity, or within 90 days of doing so. If you don't join any social insurance fund, you will be automatically affiliated to the National Fund (Caisse nationale auxiliaire/Nationale Hulpkas).
To join a social insurance fund, foreigners must submit their professional card (carte professionnelle/beroepskaart), or the necessary documents relating to their residency (for nationals from Central and Eastern Europe).