Find out what documents you will need to provide proof of sale and ownership if you are buying, selling, or gifting a vehicle. We encourage you to Visit the Fulton County DMV for immediate assistance and to keep it Local!Documents Filed at the Department of Motor Vehicles: When you buy a car at the dealership, you'll need to sign the car purchase or sale agreement along with other documents. Find out what you'll sign and why. Write out your own full name, and that of the buyer. Seller of motor vehicle or vessel must complete, sign and give this form to the purchaser.