Almanac note · Home and property
Prop 13 starts with the assessed value, not the Zestimate
If you are trying to understand a California property-tax bill, do not start with what a house might sell for today. Start with the assessed value the county is using. Prop 13 is built around that assessed value and the base-year value, which usually starts when the property changes ownership or when new construction is finished.
Put simply: the county’s number is the number that matters for the bill. A real-estate website can help you understand the market, but it does not decide the tax roll. Your county assessor is the office to check first.
Official sources
Official source trail
Reviewed June 29, 2026
California Porch explains the path. The official source is still the place to confirm the current rule, fee, form, map, deadline, or office decision.
Use the official page before you spend money, file paperwork, rely on a deadline, or change a property.
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