A self-employed person or a company that did not join a social security fund, pays no social contributions. The National Institute traces them and reminds them of their membership obligation.
This is mainly a preventive task (no membership = no payment of contributions = no coverage in case of illness, inability to work, bankruptcy, retirement, …).  

These investigative actions also have a financial objective. The NISSE is co-responsible for the financial balance of the social status, which largely consists of social contributions.

Moreover, the NISSE wants to inform citizens. Laws and legislations are often extremely complex. The NISSE has the expertise and know-how to offer advice and explanations.