You can buy both new and used cars from car dealers throughout Belgium. You can also buy second-hand cars privately. Belgium has favourable car prices in the EU market
The seller will give you: a bill of sale or invoice, a registration request (demande d'immatriculation -- formulaire rose) and a conformity certificate (certificat de conformité). If you wish to export the car you will need these documents as well as transit plates if the car is being driven.
The registration request will have two stamps on it, called 705 and 904. The 705 stamp is proof the vehicle has been through customs and the 904 is proof the car is legally registered and VAT has been paid. The conformity certificate is proof the car is up to European safety and emissions standards.
To export a Belgian car you will need to register the car on a temporary basis. Take all documents to the nearest Vehicle Registration Office (Direction Immatriculation, DIV) along with your identity documents, such as passport and proof of your permanent address.
Check how much tax you will have to pay in the country you wish to export the car to. This can vary greatly, even within the EU. You can arrange to drive yourself if you are within Europe, or organise transport via land, or sea, to your desired destination.