California Property Tax Appeal
How to Appeal Your Property Taxes in Sonoma County (2026)
Sonoma County — Santa Rosa, Petaluma, and the wine country north of the Bay — has a housing market shaped by tourism, agriculture, and a string of hard years from wildfire recovery. Values here can move sharply block by block, and when a neighborhood softens, the assessed value on your tax bill doesn't follow it down on its own.
Sonoma keeps the cost of challenging an assessment low — a $30 filing fee — and doesn't publish a separate informal-review form, so the practical first step is a call to the Assessor about a Decline-in-Value (Proposition 8) reduction. Many corrections are settled informally, without a hearing, if recent comparable sales near you came in under your assessed value.
This page walks through the Sonoma County process end to end — the November 30 deadline, the form, the $30 fee, and the informal-first path — plus an honest read on whether your home is genuinely overassessed before you file.
Sonoma County appeal — at a glance
- Appeal deadline
- July 2 – November 30
- Filing fee
- $30
- Appeal form
- BOE-305-AH
- Assessor's office
- (707) 565-1888
Check your Sonoma County home in minutes
Enter your address and get an honest, comparable-sales analysis of whether you're overassessed — $9.99, with 3 years of monitoring included.
Analyze my assessmentFlat fee. You keep 100% of your tax savings.
Is your Sonoma County home overassessed?
California property tax bills run roughly 1.1%–1.25% of a home's assessed value. At that rate, an assessment that's $50,000 too high costs a homeowner on the order of $550–$625 every single year — and it compounds until someone corrects it.
The only way to know is to compare your assessed value against what similar nearby homes actually sold for. That's exactly what a Numa analysis does: real comparable sales, an honest overassessed / fairly-assessed verdict, and a conservative savings estimate — for $9.99, with 3 years of monitoring included.
How to appeal in Sonoma County, step by step
- 1
Confirm your home is overassessed
Your case rests on recent sales of comparable homes. Gather a few similar properties nearby that sold recently, adjust for differences in size, age, and condition, and check whether they came in below your assessed value. This is the most time-consuming part of an appeal, and the quality of those comparables is what decides it.
- 2
Request an informal review with the Assessor
In Sonoma County, start with an informal Decline-in-Value (Proposition 8) review — often the fastest path, resolved without a hearing. Contact (707) 565-1888 for the informal review process..
- 3
File a formal appeal if needed
If the informal review doesn't resolve it, file form BOE-305-AH with the Assessment Appeals Board — before the November 30 deadline. You can file by mail or in person.
- 4
Present your evidence
Your comparable-sales evidence is what wins the appeal. Numa's $24.99 packet assembles it into a ready-to-file case — and if the informal review fails, the formal Appeals Board packet is included at no extra charge.
Do it yourself, or let Numa do the hard part
You can absolutely appeal on your own — the deadline, form, and steps above are all you need to file. The catch is Step 1: building the comparable-sales evidence that actually wins. Here's the honest trade-off.
Do it yourself
- Free
- Typically 5–10 hours of work
- You find, adjust, and score the comps yourself
- Amateur evidence is the top reason appeals fail
- No easy way to know if you should file at all
With Numa
- $9.99 analysis, done in minutes
- Real comparable sales, scored the way the county does
- An honest verdict — including “don't file, you're fairly assessed”
- 3 years of monitoring included
- Optional $24.99 ready-to-file evidence packet if you're overassessed
Sonoma County key dates
- Appeal window: July 2 – November 30
- Contact assessor for informal review before filing formal appeal.
- Prop 8 (decline in value): Same as regular appeal deadline.
Sonoma County property tax appeal — FAQ
What is the property tax appeal deadline in Sonoma County?
The regular appeal window runs July 2 through November 30. Contact assessor for informal review before filing formal appeal.
How much does it cost to appeal property taxes in Sonoma County?
The filing fee is $30.
Do I have to go to a hearing to lower my assessment?
Often not. In Sonoma County you can request an informal review (a Decline-in-Value / Proposition 8 request) with the Assessor first — many reductions are resolved this way without a formal hearing. If the informal review doesn't succeed, you can file a formal appeal with the Assessment Appeals Board.
How do I know if my Sonoma County home is overassessed?
Your home is overassessed if comparable homes recently sold for less than your assessed value. Numa runs that comparison for you — the same comparable-sales method the county uses — and gives you an honest verdict for $9.99, with 3 years of monitoring included.
What form do I use to appeal in Sonoma County?
Formal appeals use form BOE-305-AH, filed with the Assessment Appeals Board. Numa's packet fills in the evidence and shows you exactly how to file it.
Check your Sonoma County home in minutes
Enter your address and get an honest, comparable-sales analysis of whether you're overassessed — $9.99, with 3 years of monitoring included.
Analyze my assessmentFlat fee. You keep 100% of your tax savings.