AppealDesk

San Mateo County Property Tax Appeal — California

Rob HartleyRob Hartley·Updated February 25, 2026

San Mateo County is located on the San Francisco Peninsula in the San Francisco Bay Area of California. With an estimated population of 760,145 in 2026, it is the state's 15th largest county. Redwood City serves as the county seat, while Daly City is the most populous city, followed by San Mateo. Other notable cities include Burlingame, San Bruno, Menlo Park, and South San Francisco. Property tax appeals are particularly important here due to the county's exceptionally high home values—with a median home price of approximately $2.07 million as of early 2026—making San Mateo County one of the most expensive housing markets in the entire nation. The county's median annual property tax bill of $8,692 is substantially higher than the national median of $2,400, meaning even small assessment reductions can result in significant savings for homeowners.

Notable cities: Redwood City, Daly City, San Mateo, Burlingame, San Bruno, Menlo Park, South San Francisco

Median Home

$1,500,000

Tax Rate

1.26%

Annual Tax

$8,692

Population

760,145

2026 Appeal Deadline: November 30, 2026

For regular assessment appeals (decline in value, base year value, personal property), applications must be filed between July 2, 2026 and November 30, 2026. If November 30 falls on a weekend, the deadline extends to the next business day. For supplemental assessments, escape assessments, or roll corrections, appeals must be filed within 60 days of the mailing date on the assessment notice or postmark date, whichever is later. There are no deadline extensions or exceptions regardless of circumstances.

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

How San Mateo County Assesses Property

100%of market value

Assessed by: San Mateo County Assessor-County Clerk-Recorder & Elections (ACRE)

Assessment cycle: annual

Notices typically mailed: Spring (typically mid-May)

In San Mateo County, properties are assessed annually at 100% of their market value as of January 1st (the lien date), subject to Proposition 13 limitations. California law establishes a 100% assessment ratio, meaning the assessed value equals the full market value for newly purchased properties. For example, if your home's market value is $1,500,000 at a 100% assessment ratio, your assessed value would be $1,500,000, resulting in approximately $18,900 in annual taxes at the county's effective rate of 1.26%. However, Proposition 13 limits annual increases to 2% for properties that have not changed ownership, so long-term owners may have assessed values well below current market value.

The Appeal Process

Appeals are heard by the Assessment Appeals Board. The Assessment Appeals Board consists of three impartial commissioners who act in a quasi-judicial capacity. Hearings are public. You'll present evidence supporting your opinion of value, and the Assessor's Office will defend their valuation. The board's decision is final unless appealed to Superior Court.

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Step 1: Contact the Assessor's Office informally first. Call (650) 599-1227 within 15 days of receiving your assessment notice to request an informal Decline in Value review. This may resolve your issue without filing a formal appeal.

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Step 2: Obtain and complete the Application for Changed Assessment (BOE-305-AH). Download the form from the county website or request it from the Assessment Appeals Board Clerk at (650) 363-4573 or AAB@smcgov.org. Complete all sections accurately and provide your opinion of value.

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Step 3: Gather supporting documentation. Collect comparable property sales data, recent appraisals, photos showing property condition, repair estimates for defects, and any evidence supporting your claim that the assessed value exceeds fair market value as of January 1.

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Step 4: File your appeal with the required $30 non-refundable filing fee. Submit the original application plus two copies between July 2 and November 30, 2026 (for regular assessments). Make the check payable to 'San Mateo County AAB.' File by mail (postmarked by deadline) or in-person.

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Step 5: Attend the pre-hearing conference. Within 2-3 months, you'll be notified at least 45 days before your pre-hearing conference. This allows exchange of information between parties and may result in a stipulation (settlement) with the Assessor's Office.

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Step 6: Present evidence at the evidentiary hearing before the Assessment Appeals Board. Bring eight (8) copies of all documents. The three-member board will hear testimony from both you and the Assessor's Office. The board can lower, raise, or confirm the assessed value.

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Step 7: Receive the board's decision by mail. If you disagree with the Assessment Appeals Board's decision, you may appeal to California Superior Court. Continue paying property taxes during the appeal—if successful, you'll receive a refund with interest.

Required form: Application for Changed Assessment (BOE-305-AH)

Filing Methods

online:San Mateo County is developing an online portal system for electronic filing. Currently, applications can be downloaded from https://www.smcgov.org/ceo/assessment-appeals-board
mail:Mail to: Assessment Appeals Board, 500 County Center, 5th Floor, BOS104, Redwood City, CA 94063. Applications must be postmarked by the deadline.
in-person:Hand-deliver to Assessment Appeals Board Clerk at 500 County Center, 5th Floor, Redwood City, CA 94063. Office hours: 8:00 AM - 5:00 PM, Monday through Friday.
email:Contact AAB@smcgov.org for guidance on electronic submission options

Evidence to Bring

Comparable sales data (recent sales of similar properties in your area)Professional appraisal reportPhotographs documenting property condition or defectsRepair estimates or contractor bids for needed workIncome and expense statements (for income-producing property)Information about adverse conditions affecting value (flooding, noise, etc.)Tax bills and assessment noticesMLS listings or real estate data

San Mateo County Assessor Contact

San Mateo County Assessor-County Clerk-Recorder & Elections

Phone: (650) 599-1227

Address: 555 County Center, 1st Floor, Redwood City, CA 94063

Website: https://smcacre.gov/assessor

Online Portal: https://www.smcgov.org/ceo/assessment-appeals-board

Hours: 8:00 AM - 5:00 PM, Monday through Friday

Tax Exemptions in San Mateo County

Homeowners' Exemption

$7,000 reduction in assessed value (saves approximately $70-80 annually)

Reduces the assessed value of an owner-occupied principal residence

Eligibility: Property must be the owner's principal place of residence as of January 1st (lien date). Available to homeowners who occupy the property as their primary residence.Deadline: File by February 15 to receive the full exemption for that year. This is a one-time filing that continues automatically unless ownership or use changes.

Disabled Veterans' Exemption - Basic

$180,671 reduction in assessed value (2026 amount, adjusted annually for inflation)

Property tax exemption for 100% disabled veterans on their principal residence

Eligibility: Veterans rated 100% disabled due to service-connected injury/disease, or paid at 100% rate due to unemployability. Also available to unmarried surviving spouses. Must be principal place of residence. Discharge must be under 'other than dishonorable' conditions.Deadline: File by December 31 of the year to receive full benefit. One-time filing using Form BOE-261-G. Must include DD-214 and VA rating decision letter.

Disabled Veterans' Exemption - Low Income

$271,009 reduction in assessed value (2026 amount, requires household income below $81,131 based on prior year)

Enhanced property tax exemption for 100% disabled veterans with limited household income

Eligibility: Same disability requirements as basic exemption, but household income from the previous calendar year must not exceed the annual limit ($81,131 for 2026). Must be principal place of residence.Deadline: Annual filing required by February 15 to confirm continued income eligibility. Use Form BOE-261-G with income documentation.

Veterans' Exemption

$4,000 property value exemption

Basic exemption for honorably discharged veterans with limited property holdings

Eligibility: Honorably discharged veterans, unmarried surviving spouses, or pensioned parents of deceased veterans. Claimant cannot own property worth more than $5,000 (single) or $10,000 (married). Most homeowners do not qualify due to property value restrictions.Deadline: File by February 15 for full benefit. Contact Assessor's Office at (650) 599-1227 for application.

Official Resources

San Mateo County Assessor-County Clerk-Recorder & Elections Official Website →

Official site for San Mateo County property assessment information, exemption applications, and online services.

San Mateo County Assessment Appeals Board →

Download appeal forms, access filing instructions, and learn about the appeals process and deadlines.

San Mateo County Property Tax Payment Portal →

Pay property taxes online, view your tax bill, and access payment history through the Tax Collector's office.

California Board of Equalization - Property Tax Appeals Guide →

Statewide guidance on property tax assessment appeals, exemptions, and Publication 30 for residential property owners.

Check Your San Mateo County Assessment

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Frequently Asked Questions

What is the deadline to appeal my property taxes in San Mateo County for 2026?
For regular assessment appeals (including decline in value and base year value disputes), the filing period runs from July 2, 2026 through November 30, 2026. Applications must be postmarked or hand-delivered by the November 30 deadline—there are no extensions or exceptions regardless of your circumstances. If you're appealing a supplemental assessment, escape assessment, or roll correction, you have 60 days from the mailing date printed on your assessment notice or the postmark date, whichever is later. Missing the deadline means you lose your right to appeal that year's assessment, so mark your calendar and file promptly.
How much does it cost to file a property tax appeal in San Mateo County?
San Mateo County charges a non-refundable $30 filing fee for each assessment appeal application. The check should be made payable to 'San Mateo County AAB' and must be submitted with your application. Each property parcel and each tax year requires a separate application and separate $30 fee. If you're appealing multiple properties or multiple years, you'll need to pay $30 for each individual application. This fee covers the administrative costs of processing your appeal and scheduling your hearing before the Assessment Appeals Board, regardless of whether you win or lose your appeal.
What evidence do I need to win my property tax appeal in San Mateo County?
To succeed in your San Mateo County property tax appeal, you need compelling evidence that your property's assessed value exceeds its fair market value as of January 1st. The most persuasive evidence includes comparable sales data showing recent sales of similar properties in your area that sold for less than your assessment, a professional appraisal conducted around the lien date, photographs documenting property defects or damage, and contractor repair estimates. You should bring eight copies of all documentation to your hearing. The Assessment Appeals Board evaluates your evidence against the Assessor's evidence to determine the property's true market value. Strong, well-organized comparable sales are typically the most effective evidence for residential property appeals.
Can I appeal my San Mateo County property taxes online?
San Mateo County is currently developing an online portal system for electronic filing of assessment appeals, but the system is not yet fully operational as of 2026. For now, you can download the Application for Changed Assessment (Form BOE-305-AH) from the county website at https://www.smcgov.org/ceo/assessment-appeals-board and then submit the completed application by mail or in-person. You can also contact the Assessment Appeals Board Clerk at AAB@smcgov.org or (650) 363-4573 to inquire about current electronic submission options. Applications must be postmarked or hand-delivered between July 2 and November 30 for regular assessments, along with the $30 filing fee and two copies of your completed application.
What happens at my San Mateo County Assessment Appeals Board hearing?
Your San Mateo County assessment appeal hearing is a quasi-judicial proceeding before a three-member Assessment Appeals Board. The hearing is public, and you'll present your evidence supporting your opinion of your property's fair market value as of January 1st. You should bring eight copies of all documents, including comparable sales, appraisals, photos, and repair estimates. The county Assessor's Office will also present evidence defending their valuation. The board will ask questions and evaluate all evidence from both parties. After considering the testimony and evidence, the board can lower your assessed value, raise it, or confirm the Assessor's original valuation. You'll be notified of the decision by mail, and if your assessment is reduced, you'll receive a refund of overpaid taxes plus interest.
How much can I save by appealing my property taxes in San Mateo County?
Potential savings from a successful San Mateo County property tax appeal depend on how much your assessed value is reduced and the applicable tax rate. With San Mateo County's effective tax rate of approximately 1.26%, every $100,000 reduction in assessed value saves you about $1,260 annually in property taxes. For example, if you successfully reduce your assessment from $1,500,000 to $1,400,000 (a $100,000 reduction), you'd save approximately $1,260 per year. Given the county's high property values—with a median home price over $1.5 million—even modest percentage reductions can result in substantial annual savings. The median annual property tax bill in San Mateo County is $8,692, so a 10% assessment reduction could save nearly $870 per year.
Should I contact the Assessor's Office before filing a formal appeal in San Mateo County?
Yes, absolutely. San Mateo County strongly recommends contacting the Assessor's Office at (650) 599-1227 within 15 days of receiving your assessment notice to request an informal review through the Decline in Value Assessment Program. This informal process can resolve many valuation disputes without the need for a formal Assessment Appeals Board hearing, saving you time and the $30 filing fee. The Assessor may agree to reduce your assessment after reviewing your evidence. However, the informal review deadline (typically October 31) comes before the formal appeal deadline (November 30), and the informal review does not extend your appeal filing deadline. Therefore, if you don't receive results from the informal review by early November, you should file a formal appeal to preserve your rights while the informal review is still pending.
What is the homeowners' exemption worth in San Mateo County and how do I apply?
The California homeowners' exemption reduces your property's assessed value by $7,000, which saves approximately $70 to $80 annually in San Mateo County property taxes at the county's effective tax rate. To qualify, you must own and occupy the property as your principal place of residence as of January 1st (the lien date). This is a one-time filing using Form BOE-266—once approved, the exemption continues automatically each year as long as the property remains your primary residence. You should file by February 15 to receive the full exemption amount for that year. Many San Mateo County homeowners fail to claim this exemption, leaving money on the table. Contact the Assessor's Office at (650) 599-1227 or visit https://smcacre.gov/assessor/homeowners-exemption to obtain the application form and claim this valuable tax savings.

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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Sources: https://smcacre.gov/assessor/property-tax-relief | https://www.smcgov.org/ceo/assessment-appeals-board | https://www.smcgov.org/ceo/about-assessment-appeals | https://www.ownwell.com/trends/california/san-mateo-county | https://smcacre.gov/assessor/homeowners-exemption | https://boe.ca.gov/proptaxes/homeowners_exemption.htm | https://worldpopulationreview.com/us-counties/california/san-mateo-county | https://www.almanacnews.com/real-estate/2026/02/20/san-mateo-santa-clara-counties-top-states-priciest-housing-markets/

Last verified: 2026-02-25