Why Overassessed exists.
California homeowners overpay roughly $1,000–$3,000 a year in property taxes, every year, because the right to challenge an overassessment exists but is hidden behind paperwork. Overassessed takes that paperwork off your hands.
Stuart Altman
Founder, Overassessed
I'm the founder of Overassessed. I am not a CPA, an attorney, or a licensed property tax consultant — and after months of working through how California's property tax appeal process actually works, I think that matters less than it sounds.
I built this site after starting my own appeal. Last year I started getting letters from companies offering to lower my property taxes in exchange for a percentage of the savings. Before signing up with one of them, I wanted to understand what they'd actually be doing for that money. So I started reading. The further I got, the clearer one thing became: every California county has a free informal review process. You submit comparable sales evidence to your county Assessor's office, a certified appraiser looks at it, and your assessed value either goes down or stays the same. It cannot go up. There is no downside to filing. Most homeowners don't know any of this. The mailers don't mention it.
I'm currently going through that process myself in Alameda County, which is where I live. Once you understand how it's supposed to work, watching companies charge homeowners — including homeowners who are already stretched and looking for places to save — a quarter of their savings for what is mostly paperwork feels like exactly the kind of friction the system shouldn't have.
What I have done: read the published guidance from the California State Board of Equalization (the state authority that oversees property tax assessment) on Proposition 8 and assessment appeals; mapped the deadlines, forms, fees, and submission paths for the six California counties Overassessed serves today; and worked through the informal review for my own home. Every county page on this site lists the date its facts were last verified, with a link to the source.
What this site is not: legal advice, tax advice, or a guarantee. Property tax appeals are public-process paperwork. We help homeowners do that paperwork well. The decision still belongs to your county.
If you find an error on any page, email me at stu@overassessed.co. I read every email.
How we build our county guides
Every county page on this site is built from one master record per county — the deadlines, fees, contacts, and process specifics for that county, kept in one place so the numbers you see can't drift across pages. Those values are sourced directly from the official County Assessor's office, the County Clerk of the Board, and the California State Board of Equalization — not from third-party aggregators.
Every public learn page displays the date its county facts were last verified against the source. When a county updates its process, fees, or deadlines, we update the config and the verification date — and the change propagates through the page, the structured data, and our handbook for AI engines (/llms.txt) automatically.
We do not give legal or tax advice. We do not represent homeowners at hearings. We do not file appeals on your behalf. What we do: turn the public process into a guide a homeowner can actually follow.
Spotted something wrong on a county page?
County websites change. We aim to verify our county facts at least quarterly, but if you see something out of date, send a note to stu@overassessed.co. We'll fix it and credit you on the page.
Want to see if you're overpaying?
Enter your address and we'll compare your assessed value to comparable sales. Free. About 60 seconds.