In most states, the new owner pays sales tax on a vehicle when he registers it rather than at the time of purchase. Because of this, the sales tax due in the home jurisdiction is collected regardless of the sales tax in the jurisdiction where the vehicle was purchased.
Sales tax rates differ between states and, often, between counties within a state. Because vehicles are registered to a specific physical address, state officials can easily determine what sales tax is due when a vehicle is registered. Most states assess vehicle sales tax at this time to prevent the loss of any money that is due.