///CALIFORNIA · COUNTY GUIDE
The 2026 deadline to appeal a Santa Clara County property tax assessment is September 15, 2026. The filing window runs from July 2, 2026 to September 15, 2026.
For regular lien-date / decline-in-value assessment appeals, applications are filed with the county clerk of the board during the annual filing period. Santa Clara County’s official Assessor page states that appeal applications must be filed between July 2 and September 15. The California State Board of Equalization confirms that lien-date / decline-in-value filing periods are July 2 to either September 15 or November 30 depending on the county, and directs taxpayers to check the county deadline.
| 2026 appeal deadline | September 15, 2026 |
|---|---|
| Filing window opens | July 2, 2026 |
| File with | County of Santa Clara Clerk of the Board of Supervisors, Assessment Appeals Division |
| Governing jurisdiction | Santa Clara County Assessment Appeals Board / Clerk of the Board of Supervisors |
| 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 | Contesting Your Assessed Value | Office of the Assessor | County of Santa Clara |
| Last verified | August 16, 2026 |
The 2026 deadline is September 15, 2026. The window opens July 2, 2026. For regular lien-date / decline-in-value assessment appeals, applications are filed with the county clerk of the board during the annual filing period. Santa Clara County’s official Assessor page states that appeal applications must be filed between July 2 and September 15. The California State Board of Equalization confirms that lien-date / decline-in-value filing periods are July 2 to either September 15 or November 30 depending on the county, and directs taxpayers to check the county deadline.
Appeals are filed with the County of Santa Clara Clerk of the Board of Supervisors, Assessment Appeals Division. The governing jurisdiction is the Santa Clara County Assessment Appeals Board / Clerk of the Board of Supervisors.
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.
Last verified August 16, 2026.
Enter your address and we'll check Santa Clara 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 County of Santa Clara Clerk of the Board of Supervisors, Assessment Appeals Division before relying on it.