The value that determines vehicle taxes can vary from state to state, according to DMV.org. Some states may base tax values on the weight of the vehicle, however most states use the full price of the car before rebates or discounts, according to Edmunds.com.
Tax breaks are often given to individuals who are trading in a vehicle for a new one in many states, notes Edmunds.com. In this case, the tax value is based on the difference in value between the new vehicle and the trade-in. Depending on the dealership, sales tax may also apply to the document fees.