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California homeowner guide · Reviewed September 6, 2026California Proposition 8. When a lower market value can lower an assessment.
California's Proposition 8 is the rule homeowners usually mean when they say, "My assessment is higher than my home is worth." It can provide a temporary reduction when the property's market value on January 1 is below its factored base-year value.
The key comparison is not your purchase price from years ago and not a headline about the local market. It is the property's current market value as of the January 1 lien date against the value shown on the roll. When market value is lower, the assessor is required to enroll the lower value.
Who may have a Proposition 8 case?
A case is worth a closer look when recent, comparable sales point to a market value below your property's factored base-year value. A sharp neighborhood decline, a property-specific condition issue, or a change that affects the home's utility can matter. A home that is below last year's value does not automatically qualify. It must be below the applicable factored base-year value on the relevant January 1 date.
What a reduction does, and does not do
A Proposition 8 reduction is temporary. The county reviews a property in decline-in-value status each year. As the market recovers, the assessment can rise by more than 2 percent in a year until it reaches the factored base-year value. It cannot exceed that value unless another event, such as a change in ownership or new construction, establishes a new base-year value.
Start with the right county. California has 58 county assessors and boards. Use the California county guide to find the local assessor, clerk, filing notes, and official links for the property.
A practical first pass
- Find the assessed value and factored base-year value on your assessment notice or county property record.
- Collect sales that are genuinely similar to the property and relevant to the January 1 valuation date.
- Ask the assessor whether the county offers an informal decline-in-value review and what it requires.
- Check the county's formal appeal deadline even if you begin informally. An informal request does not automatically protect a formal appeal deadline.
Vulorean's free address check can help you see the assessed-versus-market gap. It is not legal or tax advice, and county procedures control.
Check the numbers first
See how your assessed value compares with recent comparable sales, then use your county's official process to decide whether to file.
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