* The car is registered in a state that does not have a sales tax. In this case, you will need to pay sales tax on the car when you register it in the state where you live.
* You purchased the car from a private seller. In this case, you may need to pay sales tax on the car when you register it in the state where you live.
* You are registering the car in a state that has a higher sales tax rate than the state where you purchased the car. In this case, you will need to pay the difference in sales tax when you register the car.
If you are not sure whether or not you will need to pay sales tax on your car again, you should contact the DMV in the state where you are registering the car.