In Victoria
If the car doesn’t have a compliance plate attached to it, then you need a certificate of compliance from an approved ENGINNER OR MECHANIC
This paperwork has to be given along with a RWC with the car when it is registered . it is also required that the owner pass the papers over to the new owner when the car is sold.
The certificate costs $550 along with any other costs involved ( if the car needs to be complianced like, seatbelts changed, intrusion bars installed etc)
Cheers