California Prop 8 decline in value: how it works and the November 30 deadline
When a California property is worth less than its Prop 13 value, Prop 8 lets you be taxed on the lower number. Here is how it works, which deadline applies in your county, and what to file.
- January 1: the lien date. Value is measured as of this day.
- July 2 to September 15: appeal filing period in counties that mail value notices to all property owners by August 1.
- July 2 to November 30: appeal filing period in all other counties, including Los Angeles, Orange, Riverside, San Bernardino, San Diego and Sacramento.
- November 30, 2026 falls on a Monday, so this year’s late deadline is not pushed back.
Prop 13 and Prop 8 in one minute
Under Proposition 13, a California property is assessed at its purchase price or the value of new construction, its base year value, plus no more than 2% a year. That figure is the factored base year value.
Proposition 8, passed in 1978 alongside it, covers the opposite case. If the property’s market value on January 1 is lower than its factored base year value, the assessor must enroll the lower market value. That reduced value is temporary. Each year it is reviewed again, and it can rise back toward the Prop 13 value, by more than 2% a year if the market recovers, but never above it.
Two ways to get a Prop 8 reduction
1. Ask the assessor for an informal review
Most county assessors accept a request for a decline-in-value review early in the year, before the roll closes. It is free and uses a short form or online request. Deadlines vary by county, often in the spring, so check your assessor’s site.
2. File a formal assessment appeal
If the informal review is denied, too late or not enough, you can file an assessment appeal with the county assessment appeals board. The filing period is July 2 to September 15 in counties that mail value notices to every property owner by August 1, and July 2 to November 30 in the rest. There are no extensions, and filing the appeal does not change when your taxes are due. You still pay the bill on time and receive a refund if you win.
Which counties use September 15
For the 2025 roll, the September 15 deadline applied in Alameda, Alpine, Inyo, Kings, Mono, Placer, San Francisco, San Luis Obispo, Santa Clara, Sierra and Ventura counties. Every other county used the later deadline. The list can change from year to year, so confirm on your county’s assessment appeals board site.
What makes a strong Prop 8 case
- Sales of comparable properties near January 1 at lower values.
- For income property, actual rents, vacancy and expenses showing lower net income, valued at a market cap rate.
- Evidence specific to the property: a lost anchor tenant, deferred maintenance, a lease rolling to a lower rate.
- A value conclusion as of January 1, not today. Changes after the lien date count next year.
Office, retail and some hospitality properties have been the strongest Prop 8 candidates in recent years, as values have reset below purchase prices from the 2010s and early 2020s.
How Reserve handles it
Reserve compares every California parcel’s enrolled value with market evidence as of January 1 and flags the ones worth a Prop 8 review. Levy prepares the evidence, and Reserve Tax Group files the appeal as your agent. See our California page or every deadline on the property tax calendar.
Sources
- California State Board of Equalization, letter on decline-in-value filing periods (Rule 305)
- Morgan Lewis, 2025 deadlines to dispute California property tax valuation
This article is general information, not tax or legal advice. Rules and deadlines change and vary by county. Check with the appraisal district or assessor, or ask us, before you file.
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