Do I have to move into my parents' house to keep the low property tax?

Occupancy is proved with ordinary documents, and it is worth assembling them as you go rather than after a letter arrives. The formal step is claiming the homeowners' exemption on the inherited house, which is also what starts the clock the state cares about, since that claim has to be made within one year of the transfer. If an assessor looks harder, the file gets built from the same evidence any agency uses to locate a person: voter registration, your driver's license, the address on your federal and California income tax returns, utility accounts in your own name showing real usage rather than a vacant house, bank and insurance statements, vehicle registration, where your children are enrolled in school. That one-year outside limit means the move has to happen in months, not years, because you have to be living there when you claim the exemption. Do not wait for the trust administration to finish, for the remodel, or for a sibling to make up their mind. And if a genuine move is not realistic, say so early and plan around a reassessment or a sale, because a paper occupancy is the kind of thing a county unwinds later, with interest.