Prop 8 Explained: How a Decline-in-Value Reassessment Lowers Your CA Property Tax
By Danielle Cui · February 18, 2026
Most California homeowners know Proposition 13. Far fewer know Proposition 8 — the rule that can actually lower your property tax bill in a down market. Both passed in 1978; they work together.
What Prop 8 does
Prop 13 sets your base-year value (typically your purchase price), rising at most 2% a year. But if your home's current market value drops below that Prop 13 value, Proposition 8 lets the Assessor enroll the lower market value temporarily — which means a lower tax bill.
The catch is the word temporary: once the market recovers, your assessed value can climb back up — faster than 2% a year — until it reaches your original Prop 13 base. So a Prop 8 reduction is a year-by-year benefit, not a permanent reset.
Why you usually have to ask
Assessors don't have the resources to proactively re-check every property each year, so a decline often won't be reflected automatically. You typically have to request it — either informally with the Assessor, or by filing a decline-in-value (Prop 8) appeal with your county Assessment Appeals Board. (Here's why assessments don't auto-adjust down.)
How to make the case
You prove market value with comparable sales near the January 1 lien date — recent, arms-length sales of similar homes (sales more than 90 days after the lien date don't count under §402.5). If those comps show a value below your assessed value, that gap is your reduction. (How to choose strong comps.)
Worth it?
Even a modest reduction is real money — roughly $1,200/year per $100,000 of assessed-value reduction — and you can re-file in future years if the market stays soft. Start with the step-by-step appeal guide.
Frequently asked questions
What is a Proposition 8 reduction?
A Prop 8 (decline-in-value) reduction temporarily lowers your assessed value to current market value when that market value has fallen below your Proposition 13 base-year value, reducing your property tax bill for that year.
Is a Prop 8 reduction permanent?
No. It's reviewed annually. As the market recovers, the assessed value can rise back toward your original Prop 13 base — and during recovery it can increase by more than 2% per year.
Does the assessor apply Prop 8 automatically?
Usually not. Assessors rarely re-check every property each year, so you typically have to request the reduction or file a decline-in-value appeal with comparable sales.