How to Challenge a Property Tax Assessment in California
If you think your California property is assessed too high, you can challenge it — but the target matters. You cannot appeal your tax rate or the fact that your bill went up. What you can challenge is the assessed value: if the assessor's value is higher than what your property was actually worth on the lien date, you have a case.
There are two paths, and the smart move is to try the easy one first. Here's how each works, the deadlines that matter, and the evidence that actually persuades a board.
First, know what you're actually challenging
You're challenging the assessed value, not the tax rate. In California, your assessment is generally the lower of your Proposition 13 factored base-year value or the property's market value on the January 1 lien date. If the market value on that date was lower than the value the assessor enrolled, you may be entitled to a reduction.
The two paths
- Informal decline-in-value (Prop 8) review — free, quick, no hearing. Try this first.
- Formal assessment appeal — a binding process before an appeals board, with a strict deadline. Use this if the informal review is denied or you disagree.
Step 1: Request an informal decline-in-value (Prop 8) review
If your home's market value has dropped below its factored base-year value, ask your county assessor for a Proposition 8 decline-in-value review. Most counties have a simple online form and a window (often in the spring and summer) to request one. If the assessor agrees, they temporarily lower your assessed value for that year — no hearing required. It can rise again in later years as the market recovers, up to your normal Prop 13 value.
Learn how these temporary reductions work on our Proposition 8 explainer. An informal review is easy, but it doesn't by itself preserve your formal appeal rights — so watch the appeal deadline below.
Step 2: File a formal assessment appeal
To formally contest the value, file an Application for Changed Assessment with your county's assessment appeals board (or board of equalization). There's usually little or no filing fee. Miss the deadline and you generally have to wait until next year, so this is the step where timing matters most.
| What you're appealing | Filing deadline |
|---|---|
| Regular assessment (county mails notices to all owners by Aug 1) | July 2 – September 15 |
| Regular assessment (county does not mail notices by Aug 1) | July 2 – November 30 (Dec 1 if a weekend/holiday) |
| Supplemental or escape assessment | Within 60 days of the notice |
Not sure which regular period applies? Check your county assessment appeals board's website — it states whether notices are mailed by August 1.
Step 3: Build evidence that actually wins
Appeals are won on comparable sales, not on how you feel about your bill. Assemble:
- Three to six comparable sales in your neighborhood that closed near the January 1 lien date.
- Adjustments for real differences (size, condition, lot, upgrades) between the comps and your home.
- Photos and estimates documenting condition problems, deferred maintenance, or damage.
- Any listing or appraisal showing a market value below your assessed value.
Anchor everything to the January 1 lien date. A sale six weeks before or after January 1 is far more persuasive than one from the prior spring.
Step 4: The hearing and burden of proof
If the assessor doesn't resolve your application beforehand, you present your case to the appeals board. Generally the applicant carries the burden of proving the value is wrong — but for an owner-occupied single-family home, California law shifts that burden to the assessor. Either way, come with clean, dated comparable-sales evidence. The board's decision is binding on the value, though you retain further legal options.
Keep paying while you appeal
Pay your tax bill by its due dates even with an appeal pending — otherwise you rack up penalties and interest. If you win, the county refunds the overpayment.
What you can't appeal
- The tax rate itself (it's set by law and voter-approved debt).
- That your taxes simply went up, or feel too high.
- Mello-Roos, parcel taxes, or special assessments (those have their own separate processes).
- Your neighbor's lower assessment — Proposition 13 ties value to each owner's acquisition, so lower neighboring bills are normal.
Frequently Asked Questions
How do I challenge my property tax assessment in California?
Start with a free informal decline-in-value (Proposition 8) review request to your county assessor. If that doesn't resolve it, file a formal Application for Changed Assessment with your county's assessment appeals board during the annual filing period and present evidence at a hearing.
What is the deadline to appeal a property tax assessment in California?
The regular filing period runs July 2 to September 15 in counties that mail assessment notices to all owners by August 1, and July 2 to November 30 (December 1 if the 30th is a weekend or holiday) in counties that don't. Supplemental and escape assessments must be appealed within 60 days of the notice.
What's the difference between a Prop 8 review and a formal appeal?
A Proposition 8 decline-in-value request asks the assessor directly to lower your value for a single year when market value has fallen below your factored base-year value — it's free, informal, and has no hearing. A formal assessment appeal is a binding legal process before an appeals board, with a strict filing deadline, and is the way to protect your rights if the informal review is denied.
Do I have to pay my property tax bill while I appeal?
Yes. Pay the bill by its due dates to avoid penalties and interest — you're effectively paying under protest. If your appeal succeeds, the county refunds the overpayment with interest.
Who has the burden of proof at the hearing?
Generally the applicant must show the assessed value is too high. For an owner-occupied single-family dwelling, California law shifts the burden of proof to the assessor — but you should still come prepared with strong comparable-sales evidence.
What value date does the assessor use?
The lien date, January 1. Your evidence should reflect your property's market value as of January 1 of the year you're challenging, so comparable sales close to that date carry the most weight.
Learn More
This article is general educational information about the California property-tax appeal process, not legal or tax advice. Deadlines, fees, and procedures vary by county and change over time — confirm the current rules with your county assessor and assessment appeals board, and with the California State Board of Equalization, before acting.