California Property Tax Deadlines: Every Date That Matters, by County
Lien date, tax-bill due dates, informal review windows, and formal appeal deadlines — for the six counties Overassessed serves.
If you're trying to figure out when to file something — an informal Prop 8 review, a formal assessment appeal, or a supplemental appeal — the deadline depends on which county your property is in and which type of dispute you have. This page lays out every relevant date for the six California counties Overassessed serves: Alameda, Los Angeles, Orange, San Diego, San Mateo, and Santa Clara.
What you need to know in 30 seconds
- January 1 is the lien date everywhere in California. Your home's market value on that date is what an appeal is fighting over.
- July 2 to September 15 is the formal appeal window in counties where the assessor mails Notices of Assessed Value to all owners (Alameda, Santa Clara).
- July 2 to November 30 is the formal appeal window in counties that elect the longer Rule 305 deadline (Los Angeles, Orange, San Diego, San Mateo).
- 60 days is the deadline for a supplemental or escape assessment appeal — measured from the date the notice was mailed.
- Each county runs its own informal Prop 8 review window — see the table below.
Why January 1 — the lien date — is the date everything else points to
In California, the lien date is January 1 every year. R&T § 51(a) ties every annual assessment to that date — your home is taxed on the lower of (a) its factored base year value or (b) its market value as of January 1. Every other date — when bills go out, when appeals can be filed, what comparable sales count — is anchored to the lien date.
The fiscal year for property taxes is July 1 through June 30. So your January 1, 2026 lien date determines your tax bill for the 2026-27 fiscal year, paid in two installments in late 2026 and early 2027.
The annual property tax bill cycle
The cycle is the same in every California county:
- January 1Lien date. Property values are fixed for the upcoming fiscal year.
- June or JulyAssessors finalize the roll and turn it over to the auditor.
- Late June – early JulyCounties that mail Notices of Assessed Value to all owners do so now.
- July 1Start of the new fiscal year.
- Around OctoberAnnual secured tax bills mailed.
- November 1First installment of secured property tax becomes due.
- December 10Last day to pay first installment without penalty.
- February 1Second installment due.
- April 10Last day to pay second installment without penalty.
If December 10 or April 10 falls on a Saturday, Sunday, or holiday, the postmark date for the next business day is treated as on time.
Assessment notice mailing windows by county
Whether your county mails a Notice of Assessed Value to every owner is what determines whether your formal appeal deadline is September 15 or November 30. Property Tax Rule 305(d)(1)(A)–(B) is the rule: counties that mail § 619 notices by August 1 to all real property owners on the secured roll get the September 15 deadline; counties that don't get the November 30 deadline.
| County | Mails NAV to all owners? | Notice mailed | Formal deadline |
|---|---|---|---|
| Alameda County | Yes — proactive program | Late July | September 15 |
| Los Angeles County | No — only when assessment changes | On change only | November 30 |
| Orange County | Yes since 2015 | July | November 30 |
| San Diego County | No — values posted online June 30 | Online posting only | November 30 |
| San Mateo County | Yes — Notice of Valuation | July | November 30 |
| Santa Clara County | Yes — late June | Late June / early July | September 15 |
A note on Orange County: OC mails Notices of Assessed Value to all owners (which would normally lock in the Sep 15 deadline), but the county adopted the extended Nov 30 filing deadline option that R&T § 1603 authorizes counties to use. Property Tax Rule 305 sets a floor, not a ceiling — a county that mails notices may still elect the longer window.
Informal review request deadlines, by county
The informal Prop 8 / decline-in-value review is a separate process from the formal appeal. The assessor's office handles it, there's no hearing, and most counties don't charge a fee. Each county sets its own window.
| County | Informal review window for the current roll year |
|---|---|
| Alameda County | Accepted year-round |
| Los Angeles County | July 2 – November 30 |
| Orange County | By April 30 |
| San Diego County | December 1 – April 30 |
| San Mateo County | By October 31 |
| Santa Clara County | By August 1 |
If the assessor's informal review hasn't come back by the formal appeal deadline, every one of these counties recommends filing the formal BOE-305-AH application as a backstop so you don't lose appeal rights.
Formal appeal filing windows: Sep 15 or Nov 30, depending on your county
This is the deadline that's hard to miss without consequences. Property Tax Rule 305(d)(1) ties the deadline to whether the county assessor mailed § 619 Notices of Assessed Value to all real property owners by August 1:
- Counties that mail NAVs to all owners → July 2 – September 15
- Counties that do not → July 2 – November 30
The formal appeal goes to the Clerk of the Board of Supervisors in the county where your property is located, on form BOE-305-AH (Assessment Appeal Application, current revision: Rev. 12, May 2024).
Supplemental and escape assessment appeals: 60-day clock
If you bought a home, completed new construction, or received a notice of an “escape assessment” (a back-assessment for a prior year), you don't wait for the regular appeal window. You have 60 days from the date printed on the supplemental or escape notice (or from the postmark, whichever is later) to file BOE-305-AH.
In Los Angeles County and a few other counties that have adopted a R&T § 1605 resolution, the 60-day clock can run from the tax bill rather than the notice — same form, same window, different trigger document.
If a calamity (fire, earthquake, declared disaster) caused a reassessment, you have six months from the mailing of the assessor's notice of proposed reassessment to appeal.
County-by-county deadline table
Every cell is sourced from each county's page on Overassessed (the authoritative source). Verify against your county's Clerk of the Board before relying on it.
| County | Lien date | Informal review | Formal appeal window | Filing fee | Where to file |
|---|---|---|---|---|---|
| Alameda County | Jan 1 | Accepted year-round | July 2 – September 15 | $50 | Assessment Appeals Board |
| Los Angeles County | Jan 1 | July 2 – November 30 | July 2 – November 30 | $46 | Assessment Appeals Board |
| Orange County | Jan 1 | By April 30 | July 2 – November 30 | $0 | Assessment Appeals Board |
| San Diego County | Jan 1 | December 1 – April 30 | July 2 – November 30 | $0 | Assessment Appeals Board |
| San Mateo County | Jan 1 | By October 31 | July 2 – November 30 | $30 | County of San Mateo Assessment Appeals Board |
| Santa Clara County | Jan 1 | By August 1 | July 2 – September 15 | $290 | Santa Clara County Assessment Appeals Board |
Supplemental and escape appeals: 60 days from the notice in every county above (LA County and certain other R&T § 1605 counties measure from the tax bill instead).
What if a deadline falls on a weekend or holiday?
If September 15, November 30, December 10, or April 10 falls on a Saturday, Sunday, or legal holiday, a postmark or filing on the next business day is treated as timely. This is why November 30, 2025 (a Sunday) rolled to Monday December 1, 2025 in San Diego, San Mateo, Orange County, and every other Nov 30 deadline county.
For the 2026-27 roll year, November 30, 2026 is a Monday, so it does not roll. September 15, 2026 is a Tuesday — also doesn't roll. Always check the calendar.
What you should do today, depending on the calendar
- November–DecemberIf you're in San Diego, the December 1 informal review window opens. Start gathering January 1 comps. If you're in any Nov-30 county, you've just missed the formal deadline if you didn't file — wait for next July.
- January–FebruaryLien date just passed. Now is when comparable sales need to be tracked. San Diego informal window is open (Dec 1 – Apr 30).
- March–AprilSales that close after about March 31 generally cannot be considered by an appeals board for the current year (R&T § 402.5 90-day rule). Lock in your comps.
- May–JuneCounties that mail NAVs to all owners are running their proactive Prop 8 reviews. If your county already cut your value, you may not need to file anything.
- July 2The formal appeal window opens everywhere. If you got a Notice of Valuation you disagree with, file BOE-305-AH now rather than waiting.
- Mid-July to mid-AugustMost counties' notices have arrived. If you have an informal-review-deadline-county (Santa Clara Aug 1, San Mateo Oct 31, OC by Apr 30 of the following year), file the informal request as soon as you can.
- September 15Hard deadline in Alameda and Santa Clara. Miss it and you're done for this year unless you have a supplemental.
- November 30Hard deadline in LA, OC, San Diego, and San Mateo (subject to weekend rollover).
Frequently asked questions
Property Tax Rule 305 distinguishes between counties that mail § 619 Notices of Assessed Value to all real property owners (deadline is September 15) and those that do not (deadline is November 30). The point of the rule is that homeowners need an opportunity to react after seeing the assessor's number — counties that don't notify everyone get a longer window so people can respond when they see the tax bill.
File the formal BOE-305-AH appeal anyway — every California county recommends it as a backstop. The two processes are independent; if your informal review later succeeds, you can withdraw the formal appeal. If you don't file by the deadline and the informal review comes back unfavorable after the deadline, you've lost the right to appeal that year.
Generally no. Property Tax Rule 305(d) is a hard deadline, and as the San Mateo Clerk of the Board puts it, “there are no deadline extensions or exceptions regardless of your circumstances.” The only common exception is when the assessor failed to send a notice of assessment more than 15 days before the close of the regular filing period, in which case Rule 305(d)(4) gives you 60 days from notice or bill.
No. The two systems are separate. R&T § 5097 lets you designate your appeal application as a claim for refund, which streamlines getting your money back if you win, but you still must pay your tax bill on time to avoid penalties. If you pay both installments and later win a reduction, the county refunds the difference with statutory interest.
Yes — assessment is by county, and each parcel is assessed by the county where it sits. Each parcel gets its own application, and most counties charge their per-parcel fee.
A Prop 8 reduction made under R&T § 4831(b) creates its own appeal window: 60 days from notification of the revised assessment. The 60-day clock is shorter than the regular window, so don't sleep on it.
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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. Users file their own appeals. Deadlines and fees can change — verify with your county Clerk of the Board before filing.