These documents are used to establish a complete chain of ownership. The proof of sale for a vehicle from a dealer is the Retail Certificate of Sale (MV-50) ("Dealer's Bill of Sale").Motor Vehicle, Mobile Home, Off- Highway or Vessel Description. Year. It's a good idea to get a bill of sale if you intend to buy or sell an RV. This formal document serves as proof of ownership change from seller to buyer. Use this form when sales tax was not collected at the time of purchase or when the vehicle was received as a gift. How do I fill this out? Follow these easy steps to transfer the florida title and avoid delays.