The only other thing I can think you mean is if you buy a new car in WA, take delivery, pay tax, and then move to CA. Usually if the vehicle is registered in WA (or another state) and THEN you move the other state won't tax it. However, if you try to puchase in WA while you are legally a resident of another state and take the car to that state before you register the car, the new state will collect tax (you also wouldn't qualify for the WA sales tax exemption based on residence)