If you want to contest a fine you have received, you must contact the Regional tax authority which issued the fine.
Those Regional tax authorities are Brussel Fiscaliteit/Bruxelles Fiscalité, the Vlaamse Belastingdienst or the Direction Générale opérationnelle de la fiscalité du Service Public de Wallonie. Their contact details can be found in articles 8 and 9 of the document you have received to notify you of the fine (proces-verbaal/procès-verbal).
We advise you to attach the Detailed Trip Statement to identify exactly what you are contesting. You can download it on the Road User Portal (RUP).
You automatically receive the Detailed Trip Statement, unless you have opted out of this option. If you would like to opt in again for this option, you can do so quite simply on the Road User Portal (RUP) by clicking on “My Account” and then “Manage Account” in the upper right-hand corner. Click on “EDIT” and tick the “Provide Detailed Trip Statement” box under “Billing information”. Please be aware that you cannot retro-actively activate or request a Detailed Trip Statement.