Find out what documents you will need to provide proof of sale and ownership if you are buying, selling, or gifting a vehicle. You'll need to sign the car purchase agreement (or dealer bill of sale), the title, an odometer statement, and sometimes a damage disclosure statement.This form certifies the purchase price and determines the sales tax you must pay when registering the vehicle. Use this car purchase agreement template to customize the financing information for your car along with other required details. 1 If you're financing your purchase ; 3 The actual vehicle purchase agreement ; 4 Buyer's trade in certification ; 5 Warranty disclaimer and documentary fee notice. Watch this before you finance your next car (former dealer explains how to read a purchase contract) 1. Enter the buyer's name and contact information. Information you can expect to fill out includes the car's VIN, make, and model, the name and permanent address of each party involved, and the sales amount.