If your California home is worth less on January 1 than its assessed value, you can ask the county assessor for a free review and, if that fails, file a formal appeal with your county’s Clerk of the Board — in most counties the 2026 deadline is November 30. You don’t need a lawyer, and you can start with an informal request that costs nothing. Here’s how it works.
1. Understand how your home is valued
California values homes in two ways, and your taxes are based on the lower one.
- Prop 13 base year value. When you buy a home or finish new construction, the assessor sets a “base year value,” usually your purchase price. After that, the taxable value can go up by no more than 2% a year, even if the market rises faster.
- Prop 8 decline in value. If the market value of your home on January 1 (the lien date) falls below that factored base year value, the assessor must enroll the lower market value instead.
So the question for most homeowners is simple: could your home have sold on January 1 for less than the assessed value on your bill? If yes, you may have a case. If you bought recently and think the base year value was set too high, see step 7.
2. Check your notice and your exemption
Look at your assessment notice or tax bill and check:
- Assessed value — compare it with what similar homes were selling for around January 1.
- Property facts — square footage, bedrooms, bathrooms, lot size. Errors happen.
- Homeowners’ exemption — if the home is your main residence on January 1, you can claim a $7,000 reduction in taxable value. File form BOE-266 once with the county assessor. File by February 15 to get the full exemption for that year.
3. Ask the assessor for an informal review (free)
Most county assessors will review a property for a decline in value if you ask. Some just need a phone call; others use a request form. Either way, there is no fee, and the assessor can correct errors or lower your value without a formal appeal.
Informal review windows are usually earlier than the formal appeal deadline. Two examples:
- Riverside County takes Prop 8 “Request for Review” filings through its Assessor-County Clerk-Recorder website. It asked owners to file by May 15, 2026 to be considered before the roll closed, and the county lists a final deadline of November 1.
- San Francisco accepts informal review requests for homes from January 2 to March 31.
Important: an informal review does not extend your formal appeal deadline. If the review is still pending as the appeal deadline approaches, file the appeal anyway.
4. File the formal appeal on time
The formal appeal is the Assessment Appeal Application, form BOE-305-AH. You file it with the Clerk of the Board (the clerk of the assessment appeals board) in the county where the property sits. Use your county’s version of the form. Many counties take it online.
For regular annual assessments, the filing period opens July 2. It closes on:
- September 15, if the county assessor mails value notices to all secured-roll owners by August 1, or
- November 30, if the assessor doesn’t.
For 2026, the State Board of Equalization lists 11 counties that close September 15 and 47 that close November 30. Some of the largest:
| County | 2026 regular filing period |
|---|---|
| Los Angeles | July 2 – November 30 |
| Orange | July 2 – November 30 |
| San Diego | July 2 – November 30 |
| Riverside | July 2 – November 30 |
| San Bernardino | July 2 – November 30 |
| Sacramento | July 2 – November 30 |
| Santa Clara | July 2 – September 15 |
| Alameda | July 2 – September 15 |
| San Francisco | July 2 – September 15 |
An application is on time if it’s hand-delivered by close of business on the deadline, postmarked by the US Postal Service by that date, or filed electronically where the clerk accepts e-filing.
Fees: some counties charge a fee to file. San Francisco, for example, charges a $120 non-refundable processing fee per application, with waivers for low-income filers and small disputes. Check your county’s Clerk of the Board page before you file.
5. Build your evidence
Your main evidence is sales of similar homes near January 1. Sales before January 1 are fine, but they must close no later than 90 days after the January 1 valuation date (so by about March 31). The state Board of Equalization calls using later sales the most common appeal mistake.
Good evidence includes:
- Three to five sales of homes close by and similar in size, age and condition
- Notes on how each sale differs from your home (bigger lot, remodeled kitchen, and so on)
- Photos and repair estimates for problems a buyer would pay less for
- An appraisal as of January 1, if you have one
You can also ask for an exchange of information with the assessor. Your request must be made at least 30 days before the hearing.
6. Go to your hearing
Appeals are heard by the county’s Assessment Appeals Board (in some counties the Board of Supervisors) or, for simpler cases in some counties, a hearing officer. If a hearing officer handles your case, either side can reject the recommendation, and you can ask for a full board hearing.
For an owner-occupied single-family home, the assessor carries the burden of proof. Still, come prepared:
- A one-page summary with the value you’re asking for
- Your comparable sales, with a map
- Photos and repair estimates
The board is expected to decide within two years of your filing. If it doesn’t, your opinion of value on the application can be enrolled until the board rules, with some exceptions.
7. If you bought recently: base year value appeals
If you think your purchase or new construction was valued too high, you can appeal the base year value:
- Within 60 days of the supplemental assessment notice, or
- During the regular filing period in the year the value first goes on the regular roll, or in any of the three following years.
File early. A late base year appeal can lower your value going forward, but refunds for older years may be limited.
Or let someone do it for you
You can do all of this yourself for free (aside from any county filing fee). If you’d rather not, a property tax consultant can file and argue the appeal for you. Recoup Capital handles California appeals for 30% of first-year savings, and you pay nothing if your taxes don’t go down. Get started here, or see where we work.
Sources: BOE — 2026 assessment appeals filing periods (LTA 2026/023), BOE — filing period memo (LTA 2026/016), BOE — Assessment Appeals, BOE Publication 30, Residential Property Assessment Appeals (Spanish edition), BOE — Decline in Value: How It Works, BOE — Homeowners’ Exemption, Riverside County — Prop 8 review reminder, Riverside ACR — Assessment Appeals FAQ, San Francisco Assessor — Understanding Home Values and Assessment Appeals, San Francisco — Assessment Appeals Board fees.