California has sales tax reciprocity with most other states. This means that when you register the vehicle in California, present proof of the sales tax paid to the other state. This will be subtracted from the California sales tax you owe upon registration, so you will only owe the difference (usually, California is higher, but in theory, this could reduce your California sales tax to zero). However, the registration fees that arenu2019t due to sales tax are due to each state separately, so youu2019re stuck with that, though your tags will last 9 months longer than if you had originally registered the vehicle in California in the first place.