A Certificate of Conduct is a document by which an issuing authority (e.g. the Dutch Minister of Legal Protection) declares that an applicant has not been convicted of any crime that is relevant to their role.
For example, if someone has been found guilty of drunken driving and their job involves driving (e.g. a taxi driver), it is unlikely they would receive a Certificate. On the other hand, an accountant who has committed drunken driving may still be eligible to obtain a Certificate.
When an individual applies for a Certificate, the issuing authority typically checks the Criminal Records System. This system holds data on criminal offenses and their outcomes, ranging from custodial sentences to payment in lieu of prosecution or the dropping of charges.
The issuing authority may also consult police files and reach out to the Public Prosecution Service and the probation service to gather additional information. All of this data is then studied and evaluated as a whole.