Clearly print or type all information, except signatures. The proof of sale for a vehicle from a dealer is the Retail Certificate of Sale (MV-50) ("Dealer's Bill of Sale").An RV Bill of Sale is a legal document that serves as proof of the sale and transfer of ownership of a recreational vehicle (RV) from a seller to a buyer. Planning to sell your trailer? Download one of our trailer bill of sale forms and get the job done ✔️ 38 templates available. This is typically one of the first items you'll put on the bill of sale.