If you start a commercial business, you have to prove your basic management knowledge. For some professions, you must also have specific professional knowledge.
If you do not have sufficient proofs to demonstrate your own knowledge, you can mandate someone else to provide evidence of those knowledges.
In an enterprise as a physical person following individuals can do so :
In a company, the person responsible for the daily management must demonstrate that it has the knowledge(s). In most foreign companies it's mostly called the (Managing) Director, nominated by the Shareholders Meeting. In Belgian types of companies it's called "gérant" in a SPRL or SCS and "administrateur" or "administrateur délégué" in others like as the in SA.
If the person who proves the knowledge(s) leaves the enterprise, it has 6 months to nominate another one to do so. This must be again registered at the Crossroads Bank for Enterprises by the Counter of Enterprises.
Some activities are regulated in Belgium as well as in other countries. This means that one cannot install an office at will to exercise any profession. For some professions as doctors, lawyers, accountants, etc... you have to register at a professional institute an be agreed by it. For other ones you have to register at a government institute ex.: transportation matters. Below we give the list of the activities you only can exercise in Belgium by proving the professional knowledge at the counter of enterprises before beeing registered at the BCE/KBO.
You can find an exhaustive list of European regulated professions here
Sector of cycles and motor vehicles (explanation in French)
Construction sector (explanation in French)
People care sector (explanation in French)
Other sectors (explanation in French)