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Updated 2025 Tax Year

San Mateo County
Property Tax Guide

Everything you need to know about property taxes in San Mateo County, CA. Rates, due dates, exemptions, and how it affects your monthly payment.

10 Official Sources
8 min read
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Quick Facts
Tax Rate
1.0% to 1.3% of assessed value (1% base rate plus voter-approved bonds)
1st Due
Nov 1
2nd Due
Feb 1
Exemptions
4+ Available
Section 1

How Property Tax Works

San Mateo County operates under California's property tax system, which is governed by Proposition 13 and provides funding for essential local services including schools, fire protection, libraries, and county operations. The county's assessment roll has reached a record high of over $341.1 billion for the 2025-26 fiscal year, with residential properties comprising 75.7% of the total taxable value. Property taxes in San Mateo County are based on a 1% base rate applied to the assessed value of real property, with additional voter-approved bonds and assessments that vary by location.

The effective property tax rate in San Mateo County typically ranges from approximately 1.0% to 1.3% of assessed value, depending on the specific location and local bond measures. Assessment increases are capped at 2% annually under Proposition 13, providing predictability for property owners. The county's property tax system funds critical services while maintaining the protections established by California's landmark tax limitation measures.

Section 2

What Makes Up Your Tax Bill

ComponentRateDescription
Base County Rate1.000%State-mandated base rate under Proposition 13
School DistrictsVariesLocal school district bonds and parcel taxes
City/Municipal BondsVariesCity-specific voter-approved debt service
Special DistrictsVariesFire, water, sanitation, and other local services
Mello-Roos/CFDsVariesCommunity facilities districts for infrastructure
Total Effective Rate~1.0-1.3%Combined rate varies by specific location

Note: Additional assessments beyond the 1% base rate vary significantly by city and neighborhood within San Mateo County. Property owners should check their specific tax bill for exact rates applicable to their location.

Section 3

When Are Property Taxes Due?

For the 2025/2026 tax year in San Mateo County, property taxes are due in two installments:

First Installment
Nov 1
Delinquent after Dec 10
Second Installment
Feb 1
Delinquent after Apr 10
Pro tip: If you pay through mortgage escrow, your lender splits these payments across your monthly mortgage. If you pay directly, set calendar reminders to avoid late penalties.
Section 4

Supplemental Tax Bills

Supplemental taxes are triggered by two main events: change in ownership or completion of new construction in San Mateo County. When either occurs, the property is reassessed at current market value, and a supplemental assessment reflects the difference between the new assessed value and the previous assessed value. This supplemental assessment generates a separate tax bill that is pro-rated for the remaining months in the fiscal year, which runs from July 1 through June 30.

For example, if you purchase a home in San Mateo County in October that was previously assessed at $500,000 but sells for $800,000, you would receive a supplemental tax bill for the $300,000 increase in assessed value, calculated for the 9 months remaining in the fiscal year (October through June). The supplemental tax would be approximately $2,250 (($300,000 × 1%) × 9/12 months), assuming the base 1% rate.

Example Calculation

Example 1: $300,000 Home

  • Assessed Value: $300,000
  • Less Homeowner's Exemption: -$7,000
  • Net Taxable Value: $293,000
  • Tax Rate (assumed 1.2%): × 0.012
  • Annual Tax: $3,516
  • Monthly Escrow: $293

Example 2: $600,000 Home

  • Assessed Value: $600,000
  • Less Homeowner's Exemption: -$7,000
  • Net Taxable Value: $593,000
  • Tax Rate (assumed 1.2%): × 0.012
  • Annual Tax: $7,116
  • Monthly Escrow: $593

Example 3: $1,000,000 Home

  • Assessed Value: $1,000,000
  • Less Homeowner's Exemption: -$7,000
  • Net Taxable Value: $993,000
  • Tax Rate (assumed 1.2%): × 0.012
  • Annual Tax: $11,916
  • Monthly Escrow: $993

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Section 5

Escrow & Property Taxes

Most mortgage lenders in San Mateo County require property tax escrow accounts to ensure timely payment of property taxes. Your lender collects monthly payments equal to 1/12 of your estimated annual property tax bill and holds these funds in escrow. When property taxes become due on April 1st and July 1st, your lender pays the San Mateo County Tax Collector directly from your escrow account.

Lenders typically conduct annual escrow analyses to ensure adequate funds are collected. If property taxes increase due to reassessment or new bond measures, your monthly escrow payment may be adjusted accordingly. Property owners should verify that their lender has paid taxes on time by checking with the San Mateo County Tax Collector's office or reviewing their tax bill status online. Any discrepancies should be reported immediately to both the lender and the tax collector's office.

How HonestCasa Helps
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Section 6

Frequently Asked Questions

Q: When are property taxes due in San Mateo County? A: Property taxes are due in two installments - first installment by April 1st and second installment by July 1st. Payments become delinquent after 5:00 PM on July 2nd with a 10% penalty added.

Q: How do I apply for the homeowner's exemption? A: Contact the San Mateo County Assessor's office or email assessor@smcacre.org to request a homeowner exemption claim form. You must own and occupy the property as your principal residence on January 1st to qualify for the $7,000 assessed value reduction.

Q: Can I pay my property taxes online? A: Yes, San Mateo County offers online payment options through the Tax Collector's website. You can pay by electronic check or credit card, though credit card payments may incur processing fees.

Q: How do I appeal my property assessment? A: Appeals must be filed during the Appeals Board filing period, which typically opens in July. Contact the San Mateo County Assessment Appeals Board for specific deadlines and procedures.

Q: What happens if I pay my property taxes late? A: A 10% penalty is added to delinquent payments after 5:00 PM on July 2nd. Additional penalties and interest may accrue, and the property could eventually face tax lien proceedings.

Q: How often is my property reassessed? A: Under Proposition 13, property is only reassessed upon change of ownership or completion of new construction. Annual increases are limited to 2% or the Consumer Price Index, whichever is lower.

Q: What triggers a decline in value reassessment? A: Under Proposition 8, if your property's market value drops below its assessed value, you may be eligible for a temporary reduction. Contact the Assessor's office to request a decline in value review.

Q: Do I need to file a business property statement? A: Business personal property must be reported annually by July 1st. Contact the Assessor's office for business property statement forms and requirements.

Verified Sources

Backed by 10 Official Government Sources

Every fact in this guide is sourced from official county, state, and federal documents.

01
2024/25 use category summary menlo park fire districtmenlofire.gov
02
County
San Mateo County's 2025-26 Local Assessment Roll Reaches ...smcacre.gov
03
Tax Doc
Property Tax San Mateonacdashboard.nara.gov
04
County
Assessor Important Dates - San Mateo County Clerksmcacre.gov
05
County
How to File 571-L - Assessor - San Mateo County Clerksmcacre.gov
06
County
Property Tax Bills and Refunds - San Mateo County Clerksmcacre.gov
07
County
Homeowners' Exemption - San Mateo County Clerksmcacre.gov
08
County
San Mateo County Clerksmcacre.gov
09
State
Homeowners' Exemption - California State Board of Equalizationboe.ca.gov
10
County
Residential & Commercial Property - San Mateo County Clerksmcacre.gov
All sources verified as of 2025 Tax Year

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