Sonoma County Property Tax Appeal — California

Rob Hartley·Updated February 26, 2026

Sonoma County is located in California's Wine Country region, with its county seat and largest city being Santa Rosa. As of the 2020 census, the county's population was approximately 488,863. The median home value in Sonoma County is $444,836, significantly higher than the California state median of $384,200. The county's effective property tax rate is 1.15%, higher than the national median of 1.02%, resulting in a median annual property tax bill of $5,028—more than double the national median of $2,400. Property tax appeals matter here because of the high property values and tax burden, offering homeowners potential savings through assessment challenges.

Notable cities: Santa Rosa, Petaluma, Rohnert Park, Cotati, Sebastopol, Sonoma, Healdsburg, Windsor, Cloverdale

Median Home

$444,836

Tax Rate

1.15%

Annual Tax

$5,028

Population

488,863

2026 Appeal Deadline: July 2 through November 30, 2026

For regular assessments appealing the January 1, 2026 value, applications must be filed between July 2 and November 30, 2026. For supplemental assessments (due to change in ownership or new construction), appeals must be filed within 60 days of the mailing date or postmark date on the Notice of Supplemental Assessment, whichever is later. For escape assessments, the deadline is 60 days from the notice date.

Property in Sonoma County, California — local tax assessment and appeal guide

How Sonoma County Assesses Property

100%of market value

Assessed by: Sonoma County Assessor's Office

Assessment cycle: annual

Notices typically mailed: July-August (values enrolled around July/August each year)

Under California's Proposition 13, properties are assessed at 100% of their market value at the time of purchase or new construction, establishing a base year value. This value can increase by a maximum of 2% annually unless there is new construction or a change in ownership. For example, if your home's market value is $444,836 (the county median), at California's 100% assessment ratio your assessed value would be $444,836, resulting in approximately $5,115 in annual taxes at the county's effective rate of 1.15%. However, if the current market value falls below the Proposition 13 adjusted base year value, you may appeal for a temporary Proposition 8 reduction.

The Appeal Process

Appeals are heard by the Assessment Appeals Board. At the hearing, both you and the Assessor's Office must present evidence to support your opinions of value. The Assessment Appeals Board will determine the property value based on the evidence presented by both sides. The board has two years from the application filing date to hear and render a decision.

Step 1: Before filing a formal appeal, consider submitting a BOE-305-A Informal Assessment Review form to the Assessor's Office by March 15, 2026, if you believe your property value declined as of January 1, 2026. The Assessor may agree to reduce your value without a formal hearing.

Step 2: If informal review does not resolve the issue, obtain and complete form BOE-305-AH (Assessment Appeal Application) from the Assessment Appeals Board. Include the property information, your opinion of value, and the reason for your appeal (decline in value, incorrect base year value, etc.).

Step 3: File your completed application with the Assessment Appeals Board between July 2 and November 30, 2026 for regular assessment appeals. Include any required filing fees if applicable. You must continue to pay your property taxes while the appeal is pending to avoid penalties.

Step 4: Your application will be scheduled for a hearing before the Assessment Appeals Board. Both you and the Assessor's Office will present evidence supporting your opinions of value. Prepare comparable sales data, photographs, repair estimates, and appraisals to support your case.

Step 5: The Assessment Appeals Board will determine the property value based on evidence presented by both sides. You will receive a written decision. If the board grants a reduction, you will receive a refund for any excess taxes paid.

Step 6: If you disagree with the Assessment Appeals Board decision, you may file a challenge in the Sonoma County Superior Court within six months of the board's decision.

Step 7: For appeals beyond county level, you may contact the California State Board of Equalization for guidance on state-level remedies, though most property tax appeals are resolved at the county level.

Required form: Assessment Appeal Application (BOE-305-AH)

Filing Methods

mail:Assessment Appeals Board, 575 Administration Dr., Room 100A, Santa Rosa, CA 95403

phone:Call (707) 565-2241 for forms and information

online:Download forms at https://sonomacounty.gov/Board-of-Supervisors/Services/Assessment-Appeals/

Evidence to Bring

Comparable sales data (recent sales of similar properties)Professional appraisal reportsPhotographs of property condition or defectsRepair estimates or contractor bidsIncome and expense statements for income-producing propertiesDocumentation of property damage or decline in market conditions

Sonoma County Assessor Contact

Sonoma County Clerk-Recorder-Assessor

Phone: (707) 565-1888

Address: 585 Fiscal Drive, Room 104F, Santa Rosa, CA 95403

Website: https://sonomacounty.gov/administrative-support-and-fiscal-services/clerk-recorder-assessor/assessor

Online Portal: https://sonomacounty.gov/Board-of-Supervisors/Services/Assessment-Appeals/

Hours: Monday-Friday, 8:00 AM - 5:00 PM (contact for current hours)

Tax Exemptions in Sonoma County

Homeowners' Exemption

$7,000 reduction in assessed value (approximately $70 in annual tax savings)

Reduces the assessed value of an owner-occupied primary residence

Eligibility: Must own and occupy the property as your principal place of residence on January 1 of each yearDeadline: One-time filing with the Assessor by February 15 to receive full exemption for that year; once filed, automatically renews annually

Disabled Veterans' Exemption - Basic

$175,298 exemption from assessed value for 2026 (adjusted annually for inflation)

Property tax exemption for the principal residence of qualifying disabled veterans or their unmarried surviving spouses

Eligibility: Veterans rated 100% disabled due to service-connected injury or disease, or compensated at 100% due to unemployability; unmarried surviving spouses also qualifyDeadline: File anytime; retroactive filing available up to 8 years; one-time filing for basic exemption

Disabled Veterans' Exemption - Low Income

$262,950 exemption from assessed value for 2026 if household income does not exceed $78,718 (2025 income, adjusted annually)

Enhanced property tax exemption for qualifying disabled veterans with limited household income

Eligibility: Same disability requirements as basic exemption, plus household income limitation; requires annual re-filingDeadline: Must file annually by February 15 for low-income exemption

Veterans' Exemption

$4,000 exemption

Basic exemption for qualifying veterans with limited property holdings

Eligibility: Veterans with honorable discharge who own property worth no more than $5,000 if single or $10,000 if married; must have served during qualifying war or campaignDeadline: File with County Assessor's Office

Official Resources

Sonoma County Assessor's Office →

Official website for property assessments, exemptions, forms, and assessment information for Sonoma County.

Sonoma County Assessment Appeals Board →

Information on filing property tax appeals, downloadable forms, hearing schedules, and appeal procedures for Sonoma County.

California State Board of Equalization - Assessment Appeals →

Statewide resources on property tax assessment appeals, including Publication 30 (Residential Property Assessment Appeals guide) and filing deadlines.

Sonoma County Property Search →

Online tool to search property information, assessed values, and parcel data for properties in Sonoma County.

Check Your Sonoma County Assessment

Enter your address to see if your Sonoma County property is overassessed.

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Frequently Asked Questions

What is the deadline to file a property tax appeal in Sonoma County for 2026?

For regular assessment appeals challenging the value as of January 1, 2026, you must file your Assessment Appeal Application (form BOE-305-AH) between July 2 and November 30, 2026. This deadline applies to annual roll values. However, if you received a supplemental assessment due to a property purchase or new construction, you have 60 days from the mailing date or postmark on your supplemental assessment notice to file an appeal. Missing these deadlines means you cannot appeal that assessment year, so it's critical to check your assessed value when it becomes available in July or August and act promptly if you disagree with the valuation.

How do I file a property tax appeal in Sonoma County online?

Sonoma County allows you to download the Assessment Appeal Application (form BOE-305-AH) from the county website at https://sonomacounty.gov/Board-of-Supervisors/Services/Assessment-Appeals/. After completing the form with your property information, assessed value, your opinion of value, and reasons for the appeal, you must submit it to the Assessment Appeals Board at 575 Administration Dr., Room 100A, Santa Rosa, CA 95403. You can also call (707) 565-2241 to request forms and information. While you can download forms online, the actual submission typically requires mailing or delivering the completed application to the Appeals Board. Make sure to keep copies of everything you submit for your records.

What is the homestead exemption worth in Sonoma County?

In Sonoma County, the Homeowners' Exemption reduces your property's assessed value by $7,000, which translates to approximately $70 in annual property tax savings. To qualify, you must own and occupy the property as your principal place of residence on January 1st of each year. This is a one-time filing—once you submit form BOE-266 to the Assessor's Office, the exemption automatically renews each year as long as you continue to meet the eligibility requirements. First-time filers should submit their application by February 15 to receive the full exemption for that year, though you can file anytime after becoming eligible. This exemption is available to all qualifying homeowners regardless of income, age, or veteran status.

What happens at an Assessment Appeals Board hearing in Sonoma County?

At an Assessment Appeals Board hearing in Sonoma County, both you (the property owner or your representative) and the Assessor's Office will present evidence to support your respective opinions of your property's value. You should bring comparable sales data, photographs, appraisal reports, repair estimates, or other documentation that supports your claim that the assessed value is too high. The hearing is quasi-judicial, meaning the board members will act as impartial judges weighing the evidence from both sides. After reviewing all evidence and hearing testimony, the Assessment Appeals Board will determine the property's fair market value based on what was presented. The board has the authority to increase, decrease, or maintain the current assessed value. You will receive a written decision, and if the board reduces your assessment, you'll receive a refund for any excess taxes you paid while the appeal was pending.

How much can I save by appealing my property taxes in Sonoma County?

Your potential savings from a successful property tax appeal in Sonoma County depends on how much the Assessment Appeals Board reduces your assessed value and the county's effective tax rate of 1.15%. For example, if your home is assessed at $500,000 but you successfully prove its market value is only $450,000, that's a $50,000 reduction in assessed value. At the 1.15% tax rate, this would save you approximately $575 annually. With the median home value in Sonoma County at $444,836, even a 5% reduction ($22,242) would save approximately $256 per year, and a 10% reduction would save about $511 annually. These savings continue each year until your property value increases again. Given that Sonoma County's median annual tax bill is $5,028—well above the national median—homeowners have significant potential savings if they can demonstrate their property is overvalued.

What evidence do I need to win a property tax appeal in Sonoma County?

To win a property tax appeal in Sonoma County, you need compelling evidence that your property's market value as of January 1 is less than the assessed value on your tax roll. The most persuasive evidence includes recent comparable sales of similar properties in your neighborhood that sold for less than your assessed value, ideally within the past six months. A professional appraisal conducted as of January 1 by a licensed appraiser carries significant weight. You should also bring photographs documenting any property defects, damage, or deferred maintenance that affects value, along with contractor estimates for needed repairs. For income-producing properties, provide actual income and expense statements showing the property generates less revenue than the assessed value suggests. Additionally, evidence of declining market conditions in your area, such as market reports or statistics, can support your case. The key is presenting objective, factual evidence that contradicts the Assessor's valuation, not just your opinion that the value is too high.

Can I get an informal review before filing a formal appeal in Sonoma County?

Yes, Sonoma County offers an informal assessment review process that can save you time and effort before filing a formal appeal. If you believe your property's market value declined below its assessed value as of January 1, 2026, you can complete form BOE-305-A (Informal Assessment Review) and submit it to the Assessor's Office by March 15, 2026. This informal process allows the Assessor to review your evidence and potentially agree to reduce your assessed value without the need for a formal hearing before the Assessment Appeals Board. You should include supporting documentation such as comparable sales data or an appraisal with your informal review request. If the Assessor agrees with your evidence, they will reduce your assessment directly. However, if the Assessor does not agree or you're unsatisfied with the outcome, you still have the right to file a formal appeal with the Assessment Appeals Board between July 2 and November 30, 2026.

Do I have to pay my property taxes while my appeal is pending in Sonoma County?

Yes, you must continue to pay all property taxes on time while your appeal is pending in Sonoma County. Filing an assessment appeal does not relieve you of the responsibility to pay your property tax bills by their due dates, regardless of how unfair you believe the assessment to be. If you fail to pay your taxes on time, you will incur penalties and interest charges that cannot be avoided or refunded, even if you ultimately win your appeal. However, if the Assessment Appeals Board grants a reduction in your assessed value, Sonoma County will issue a refund for any excess taxes you paid based on the higher assessment. This refund will include the difference between what you paid and what you should have paid at the reduced assessment amount. The Assessment Appeals Board has up to two years from your application date to conduct the hearing and issue a decision, so continue making all tax payments during this period to protect yourself from penalties.

For state-wide appeal information including California's assessment ratio and deadlines, see our California Property Tax Appeal Guide →

Considering professional help with your appeal? Compare pricing, coverage, and pros/cons in our Best Property Tax Appeal Services (2026) or browse side-by-side service comparisons →

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← All California property tax appeal info

Sources: https://sonomacounty.gov/administrative-support-and-fiscal-services/board-of-supervisors/services-and-information/assessment-appeals | https://sonomacounty.gov/administrative-support-and-fiscal-services/clerk-recorder-assessor/assessor | https://www.ownwell.com/trends/california/sonoma-county | https://boe.ca.gov/proptaxes/homeowners_exemption.htm | https://boe.ca.gov/proptaxes/dv_exemption.htm

Last verified: 2026-02-26