///CALIFORNIA · COUNTY GUIDE
The 2026-2027 deadline to appeal a Alameda County property tax assessment is September 15, 2026. The filing window runs from July 2, 2026 to September 15, 2026.
Regular assessment appeals must be filed between July 2 and September 15. Supplemental or escape assessment appeals must be filed within 60 days of the notice date or postmark, whichever is later.
| 2026-2027 appeal deadline | September 15, 2026 |
|---|---|
| Filing window opens | July 2, 2026 |
| File with | Alameda County Clerk of the Board, Assessment Appeals Unit / Assessment Appeals Board |
| Governing jurisdiction | Alameda County Assessment Appeals Board / Clerk of the Board |
| After a successful appeal | A Proposition 8 decline-in-value reduction is reviewed every year and holds while the market supports it. |
| Can a board raise the value? | Yes — see below (Cal. Rev. & Tax. Code §1610.8) |
| Deadline source | Assessment Appeals - Clerk of the Board of Supervisors - Alameda County |
| Last verified | August 16, 2026 |
The 2026-2027 deadline is September 15, 2026. The window opens July 2, 2026. Regular assessment appeals must be filed between July 2 and September 15. Supplemental or escape assessment appeals must be filed within 60 days of the notice date or postmark, whichever is later.
Appeals are filed with the Alameda County Clerk of the Board, Assessment Appeals Unit / Assessment Appeals Board. The governing jurisdiction is the Alameda County Assessment Appeals Board / Clerk of the Board.
California assessments start from a Proposition 13 base-year value that rises about 2% a year. Proposition 8 requires the assessor to enroll the lower of that factored base value or the property's current market value, so when the market falls below the roll, a decline-in-value appeal applies. Several counties offer an informal review with the assessor first; formal appeals go to the county Assessment Appeals Board, and a Prop 8 reduction is reviewed every year, holding while the market supports it.
It's possible — a California Assessment Appeals Board equalizes the roll by reducing or increasing an assessment (Cal. Rev. & Tax. Code §1610.8), and the Proposition 13 ceiling protects decline-in-value appeals, not base-year disputes. That's why we check for that exposure before filing: we don't file when we see it, and if it surfaces after filing we withdraw.
Enter your address and we'll check Alameda County's own records at no cost. If there's no case, we'll tell you that too.
Serving greater Los Angeles.
California property tax appeals. Any estimate is based on county assessment data and public records and is not a guarantee of any outcome. Representation and fee terms are provided in writing before any filing. Deadline information reflects published county materials as of the date shown above — verify with the Alameda County Clerk of the Board, Assessment Appeals Unit / Assessment Appeals Board before relying on it.