Find out what documents you will need to provide proof of sale and ownership if you are buying, selling, or gifting a vehicle. Pay vehicle sales tax, prove the sales tax was paid or prove that a vehicle registration is exempt from sales tax.I accidentally put a deposit on a vehicle and signed a contract. Can I back out of the deal? Watch this before you finance your next car (former dealer explains how to read a purchase contract) You must complete, sign and submit a Notice of Sale to our office within 30 days of selling a vehicle, vessel or mobile home. A vehicle purchase agreement or vehicle contract is very important. Here are the templates that you can download and print. 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.