Alameda County property tax deadlines for 2026
The two appeal windows, the bill due dates, and what to do if you're late — all specific to Alameda County.
Alameda County has two property tax appeal deadlines, because it has two separate processes. The free informal review with the Alameda County Assessor's Office: Accepted year-round. The formal appeal with the Assessment Appeals Board: July 2 – September 15, with a $50 filing fee. Both measure your home's value as of the same date: January 1, the lien date.
Everything on this page is specific to Alameda County. For how the deadlines work statewide — and why some counties' formal deadline is September 15 while others run to November 30 — see the California-wide deadlines guide. For the full step-by-step appeal process here, see the Alameda County appeal guide.
The two appeal deadlines in Alameda County
Free · No hearing
Informal decline-in-value review
- Window
- Accepted year-round
- Form
- Decline-in-Value Review Application
- Submitted to
- Alameda County Assessor's Office
- Fee
- Free
- Typical response
- a few weeks
A county appraiser reviews your comparable sales evidence. Your value goes down or stays the same — it cannot be raised through this process.
Binding · Preserves appeal rights
Formal assessment appeal
- Window
- July 2 – September 15
- Form
- BOE-305-AH
- Heard by
- Assessment Appeals Board
- Fee
- $50
Alameda County recommends filing the formal appeal even while an informal review is pending, so a slow informal answer can't cost you the year.
The Alameda County property tax year at a glance
| Date | What happens | Why it matters |
|---|---|---|
| Jan 1, 2026 | Lien date | Your home's value for this year's bill is fixed as of this date. All appeal evidence points back here. |
| July 2 – September 15 | Formal appeal window | File BOE-305-AH with the Clerk of the Board. |
| Nov 1 / Dec 10 | First installment | First property tax installment due Nov 1, delinquent after Dec 10. Pay it even if your appeal is pending — you get a refund with interest if you win. |
| Feb 1 / Apr 10 | Second installment | Second installment due Feb 1, delinquent after Apr 10. |
The informal review window (Accepted year-round) runs on the Alameda County Assessor's Office's schedule — see the cards above. Supplemental and escape assessments have their own clock: generally 60 days from the date printed on the notice.
Not sure the deadline matters for you yet? Start with whether you're overassessed at all — free, about 60 seconds.
Check my propertyWhat if I missed a deadline?
Missed the informal window? If the formal window (July 2 – September 15) is still open, file the formal appeal — same evidence, and your appeal rights are preserved with a binding decision at the end.
Missed both? For a regular decline-in-value case, you wait for the next January 1 lien date and file in next year's windows. The deadlines aren't extendable, but nothing stops you from preparing early — the evidence rules reward sales close to the lien date, so the strongest comps for next year's appeal close between this fall and next March.
Got a supplemental or escape assessment notice? Those carry their own appeal window — generally 60 days from the date on the notice — independent of the windows above.
Who to contact in Alameda County
Alameda County Assessor's Office
Informal decline-in-value reviews
- Phone: 510-272-3787
- Website: www.acassessor.org
Clerk of the Board — Assessment Appeals Board
Formal assessment appeals
- Phone: 510-272-6352
- Mail: Assessment Appeals Board, 1221 Oak Street, Suite 536, Oakland, CA 94612
Common questions
When is the deadline to appeal property taxes in Alameda County?
There are two separate deadlines. The free informal review with the Alameda County Assessor's Office: Accepted year-round. The formal appeal with the Assessment Appeals Board: July 2 – September 15. They are independent processes — if the informal review hasn't come back before the formal window closes, file the formal application as a backstop so you don't lose your appeal rights for the year.
Does it cost anything to appeal in Alameda County?
The informal decline-in-value review is free. The formal appeal to the Assessment Appeals Board has a $50 filing fee. In both cases the evidence is the same: recent comparable sales showing your home's market value on January 1 was below your assessed value.
What form do I need for a Alameda County property tax appeal?
For the informal review, Alameda County uses the Decline-in-Value Review Application form, submitted to the Alameda County Assessor's Office. For the formal appeal, you file BOE-305-AH with the Clerk of the Board during the July 2 – September 15 window.
What if I miss the Alameda County appeal deadline?
If you miss the informal window but the formal window (July 2 – September 15) is still open, file the formal appeal. If both have closed, you generally have to wait for the next January 1 lien date and file in next year's windows — current-year deadlines aren't extendable for a regular decline-in-value case. Exceptions exist for supplemental and escape assessments, which carry their own clock: generally 60 days from the date on the notice.
Deadlines only matter if you're overassessed.
Enter your Alameda County address and we'll compare your assessed value to recent comparable sales — free, in about 60 seconds.
Deadlines and fees above are sourced from the county's published materials and reviewed when the county publishes updates — but counties can change dates and fees mid-season. Confirm on the county website before relying on a specific date. Overassessed provides estimates based on publicly available data and AI-generated analysis. This is not a formal appraisal, legal advice, or tax advice. Results are not guaranteed, and appeal outcomes depend on county review.