If so, Georgia law requires that the finance agreement be in writing in a retail installment contract. Completing this form: This form must be completed in its entirety, legibly printed or typed.Section A: Record the vehicle's information. 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. Vehicle Payment Plan Agreement. A vehicle payment plan agreement is a contract between a buyer and seller of a vehicle that agrees to installment payments. I'm gonna break down all the terms and conditions so you can understand what it means and we're gonna fill that out so you can have a real-life example of it. 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.