We have had two clients in the last two weeks come in to register trailers that they bought out of state from private parties. In both cases the trailers were boat trailers and were thrown in with the purchase of watercraft. Also in both cases our clients had bill of sales from the prior owners but nothing that proved the persons who sold the trailers actually owned them. What constitutes proof of ownership? The usual proof is an old registration or a title. Unfortunately, in many cases people are not required to title a trailer depending on its load capacity or state where the trailer is kept. In that case you want to make sure you get a prior registration. If the vehicle was never registered then you will need something else like perhaps a purchase contract from a dealer. We sent both transactions to the RMV just to see if we got lucky while the buyers tried to get the proof of ownership from the sellers. In both cases the transactions were turned away. Remember, when buying a trailer from a private party make sure you get proof of ownership.