The General Operating License is mandatory in order to register a car and take it out on the road. The official document required for the General Operating License is the car registration document. In this document, among other things, information about engine cubic capacity, power, emissions classification, seats, key number or trailer loads are included, as well as modifications to the car with the official approval of an inspection body like TÜV or Dekra, (wide tyres, body panels, etc.). If substantial changes are made to a car which the owner does not have entered in the registration document, the General Operating License becomes invalid.