Q: If you buy a vehicle and haul it home on your trailer, do you need shipping papers still?
A: Some factors for the answer are if the vehicle purchased is being transported on the trailer from one point to its destination for a non-commercial purpose and not for resale, then there are no additional documents required, just proof of ownership.

If the vehicle was to be driven from the place of purchase to the destination, then it would need the proper registration for that state and then registered permanently in the home state.

Back to the original scenario, before that transported vehicle is put into service on a public street, it will have to be registered in the home state.