It is more than just a formality. To no longer be considered a CA resident for tax purposes you need to abandon your CA domicile and establish a new one. The CA

It is more than just a formality. To no longer be considered a CA resident for tax purposes you need to abandon your CA domicile and establish a new one. The CA franchise tax board is more aggressive at pursuing taxes owed than most states. If you spend more than half of your nights in CA, it is very likely you will be a resident for tax purposes. Presumably he will hire experts and listen to their advice, and he sold all property in CA. But lots of people get caught trying to dodge these taxes unsuccessfully.