Road vehicles and watercraft

Grenzwächter kontrolliert die Papiere.

Vehicles on which duty has not been paid (cars, boats, motorbikes, etc.) must be declared to Swiss Customs. 

Travellers domiciled abroad may import vehicles into Switzerland for their own personal use without declaring them. 

There are different sets of rules depending on whether you are: 

Please note that declaring motor vehicles and trailers is only possible for goods for resale during customs office working hours. As a rule, normal office hours from Monday to Friday are applicable; some customs offices are also open on Saturday morning. Full details on the opening hours can be found in the border crossings and customs offices, opening hours section.

https://www.ezv.admin.ch/content/ezv/en/home/information-individuals/road-vehicles-and-watercraft.html