Compare the right values
A Prop. 8 issue exists when market value as of January 1 is below the property's factored base-year value—not simply because a nearby home sold for less.
California Proposition 8: a practical homeowner guide
Proposition 8 permits a temporary assessed-value reduction when a California property's market value on January 1 falls below its factored base-year value. It is separate from Proposition 13's base-year framework and separate from a formal assessment appeal. In Riverside, Los Angeles, and San Diego, Valuvia offers the Prop 8 Informal Request Package (filled informal form plus qualifying comps) on Step 2 of checkout, alongside the full appeal package. Application deadlines differ by county and by product (for example, Riverside informal requests must be received by November 1, 2026, while Riverside and Los Angeles formal appeals run through November 30, 2026). San Diego formal filing uses that county’s current Clerk of the Board instructions. For county-specific filing information, see our supported counties guide.
Gather January 1 evidence
Use verified comparable sales and property-specific facts that help explain market value on the lien date. County instructions determine acceptable dates and materials.
Choose the correct path
An assessor's informal review and a formal assessment appeal are different procedures. Preserve any formal filing deadline even while an informal review is pending.
Review future assessments
A decline-in-value reduction is temporary. The assessor may restore value in later years as the market recovers, up to the factored base-year value.
Informal review versus formal appeal
| Informal Prop. 8 request | Formal assessment appeal |
|---|---|
| Reviewed by the county assessor | Heard through the county assessment appeals process |
| County-specific form or review process | Formal application, filing period, and procedural rules |
| Usually does not preserve a formal appeal deadline | Must be timely filed under the applicable county rules |
Official resources
- California BOE — Decline in Value / Proposition 8
- California BOE — Assessment Appeals overview
- Los Angeles County Assessor — Decline in Value
- Los Angeles County — Formal assessment appeals
- Riverside County — Assessment Appeals Division
County rules, forms, and dates can change. The government source and the notice you received control. Valuvia is not a county agency, law firm, tax adviser, or appraisal service.