Which vehicles require a Camper Access Pass (€66)?

A Camper Access Pass is required for all vehicles that have a trailer (such as a box or box trailer) or a caravan attached - no matter how heavy they are.
Same applies for every motorhome or converted van (below 3.5 tons) that is entered in field 5 of the vehicle registration certificate.
All other vehicles weighing more than 3.5 tons must have a Camper Access Pass.