There are various other types of vehicles, including trailers, caravans and boats that must be registered.

http://www.vicroads.vic.gov.au...

http://www.vicroads.vic.gov.au/Home/Registration/WhatHasToBeRegistered/OtherVehiclesBoatsAndRegistrationIssues/

Registering your vehicle makes sure it can be identified if it goes missing or is in an accident and that it meets necessary safety and environmental standards. Includes Registration fees; Buying and selling; How to register or transfer; Renewing registration; Defects and suspensions; Change of personal details; Change of vehicle details; Permits; and Number plates.

http://www.vicroads.vic.gov.au...

http://www.vicroads.vic.gov.au/Home/Registration/