Lower your Contra Costa County property taxes
The Contra Costa County Assessor sets your value each January 1. Owners can ask for a Prop 8 Request for Value Review or file a formal appeal, and both are due November 30. 30% of first-year savings, only if you save.
What a too-high value costs you
If your home is assessed at $950,000 but similar homes point to about $880,000, you're taxed on $70,000 too much. At a 1.15% rate that's about $807 a year. Our fee would be $242; you'd keep $565.
What gets missed in Contra Costa
- The free Prop 8 request. The Assessor's Request for Value Review is due November 30 and uses sales before March 31. Many owners skip it and go straight to a paid appeal.
- One application per parcel. The $40 appeal fee applies to each parcel and each tax year.
- Condition. The roll can't see an original kitchen, a worn roof or foundation work.
- Wrong comparisons. Sales from Lamorinda or the San Ramon Valley used for a home in a different market.
Insider tip: Send the Assessor's Prop 8 Request for Value Review with up to three comparable sales from before March 31. Keep paying your tax bills while it's reviewed.
Reviewed by the founder
Julien reviews every Contra Costa case personally and tells you the value we’ll ask for before anything is filed.
Get my free reviewContra Costa County calendar
| January 1 | Valuation date for the 2027–28 roll |
| March 31 | Last day for sales that can support a January 1 value (90 days) |
| July 2 – November 30, 2027 | Formal appeal window with the Assessment Appeals Board ($40 per parcel) |
| By November 30 (2026 form) | Prop 8 Request for Value Review due to the Assessor; confirm the 2027 date on the new form |
| Within 2 years of filing | Assessment Appeals Board must decide unless you agree to extend |
| December 10, 2027 / April 10, 2028 | First / second tax installment delinquent if unpaid |
Sources: Contra Costa Assessor — Request for Value Review (Prop 8) · Contra Costa County — Assessment Appeals · Contra Costa Clerk of the Board — Fee schedule · BOE LTA 2026/023 — filing periods. Dates are checked each year; confirm with the county for your property.
Exemptions to check
The homeowners' exemption takes $7,000 off the taxable value of your main home; file Form BOE-266 by February 15 for the full amount. Disabled veterans may qualify for a much larger exemption, and Prop 19 lets owners 55 and over move their tax base. We check your exemptions free at sign-up.
Contra Costa questions
Is there a fee to appeal in Contra Costa County?
Yes. $40 for each application, and you need a separate application for each parcel and each tax year. Mail it with a check to the Assessment Appeals Board in Martinez.
What's the difference between the Prop 8 request and an appeal?
The Prop 8 Request for Value Review goes to the Assessor. The formal appeal goes to the Assessment Appeals Board, which holds a hearing.
I missed November 30. Now what?
Sign up anyway. We'll prepare a review request for the January 1, 2027 value and file in the window that opens July 2, 2027.