You need a California Trailer Bill of Sale form to register your trailer with the DMV after purchasing it from a private party. New Trailer and Off-Highway Vehicle (OHV) Report of Sale.Utilize our Trailer Bill of Sale to document the sale of a trailer, ensuring protection for both the buyer and the seller. For a motor vehicle bill of sale, the buyer must keep an original copy to register with the DMV. How to Register a Vehicle in California. If you are completing a bill of sale to satisfy a vehicle registration requirement, the law requires that you provide a copy to the DMV. This customizable template ensures a smooth transfer of ownership, protecting both buyers and sellers with clear documentation in the state of California. Enter the identification number and vehicle description. 2. Fill in the seller's and buyer's details with names and addresses. 3. Learn how to sell a travel trailer in Texas with our comprehensive RV Bill of Sale guide.