HonestCasa logoHonestCasa
All Tax Guides
Updated 2025 Tax Year

Sonoma County
Property Tax Guide

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

10 Official Sources
8 min read
Calculate Your True CostMortgage Calculator
Quick Facts
Tax Rate
1.1% to 1.4% of assessed value (1% base rate plus voter-approved assessments)
1st Due
Nov 1
2nd Due
Feb 1
Exemptions
5+ Available
Section 1

How Property Tax Works

Sonoma County's property tax system operates under California's Proposition 13 framework, with a base rate of approximately 1% of assessed value plus additional voter-approved assessments. Property taxes fund essential services including schools (48% of collections), special districts (8%), cities (9%), and redevelopment activities (8%). The county collected over $1.2 billion in property taxes for 2025-26, making it the primary funding source for local government services, public schools, fire protection, and infrastructure maintenance.

Effective tax rates in Sonoma County typically range from 1.1% to 1.4% of assessed value, depending on your property's location and applicable special assessments. Your property's assessed value is capped at a 2% annual increase under Proposition 13, providing predictable tax growth for long-term homeowners. New purchases are assessed at current market value, and significant improvements trigger reassessment of the enhanced value.

Section 2

What Makes Up Your Tax Bill

ComponentRate RangeDescription
Base County Tax~1.00%Core county services, mandated 1% under Proposition 13
School Bonds0.05% - 0.15%Voter-approved school district bonds for facilities
City Bonds0.02% - 0.08%Municipal bonds for local infrastructure (varies by city)
Special Districts0.03% - 0.10%Fire districts, hospital districts, library districts
Mello-Roos/CFDs0.10% - 0.25%Community facilities districts (newer developments)
Total Effective Rate1.10% - 1.40%Combined rate varies by property location

Note: Rates vary significantly based on property location within Sonoma County. Rural properties may have different special district assessments than urban properties.

Section 3

When Are Property Taxes Due?

For the 2025/2026 tax year in Sonoma 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 ownership changes (sales, transfers) or new construction that increases your property's assessed value. When you purchase property, the difference between the previous assessed value and your purchase price creates additional taxable value, prorated from the ownership change date to the end of the fiscal year (June 30).

Calculation Example: If you buy a $800,000 home in January with a previous assessed value of $600,000, you'll receive a supplemental tax bill for the $200,000 difference. At a 1.25% effective rate, this equals $2,500 annually, or approximately $1,250 for the six-month period (January-June). Supplemental bills are mailed at least 35 days after the assessment notice and have separate due dates from regular tax bills.

Example Calculation

$300,000 Home (1.20% effective rate)

  • Assessed Value: $300,000
  • Less Homeowner Exemption: -$7,000
  • Net Taxable Value: $293,000
  • Annual Tax: $293,000 × 1.20% = $3,516
  • Monthly Escrow: $293/month

$600,000 Home (1.25% effective rate)

  • Assessed Value: $600,000
  • Less Homeowner Exemption: -$7,000
  • Net Taxable Value: $593,000
  • Annual Tax: $593,000 × 1.25% = $7,413
  • Monthly Escrow: $618/month

$1,000,000 Home (1.30% effective rate)

  • Assessed Value: $1,000,000
  • Less Homeowner Exemption: -$7,000
  • Net Taxable Value: $993,000
  • Annual Tax: $993,000 × 1.30% = $12,909
  • Monthly Escrow: $1,076/month

See How Taxes Affect Your Payment

Property taxes are just part of your total monthly cost. Get the full picture.

Calculate Now
Section 5

Escrow & Property Taxes

Most mortgage lenders require property tax escrow accounts, collecting 1/12 of your annual tax bill with each monthly payment. Lenders typically collect 2-3 months of additional taxes at closing to ensure adequate funds for payment. Your lender pays the November 1st and February 1st installments directly to Sonoma County on your behalf.

Verify your escrow account annually when you receive your tax bill, as assessment changes or rate adjustments may require escrow payment modifications. If your property taxes increase due to reassessment or new voter-approved bonds, your lender will adjust monthly escrow collections and may require a one-time catch-up payment. You can request escrow account statements from your lender and should review them for accuracy, especially after receiving supplemental tax bills that may not be immediately reflected in escrow calculations.

How HonestCasa Helps
  • Understand whether your escrow is set correctly
  • See how rising taxes will change your monthly payment
  • Plan ahead instead of being surprised by "shortage" letters
Section 6

Frequently Asked Questions

Q: When are property taxes due in Sonoma County? A: First installment due November 1st (delinquent December 10th at 5 PM), second installment due February 1st. You can pay the full year by December 10th to avoid the February payment.

Q: How do I apply for the homeowner exemption? A: File with the Sonoma County Assessor's Office by February 15th of the tax year. The $7,000 exemption saves approximately $70-90 annually and remains in effect until you sell or stop occupying the property as your primary residence.

Q: Can I appeal my property assessment? A: Yes, file an assessment appeal by November 30th if you believe your assessed value exceeds fair market value. The county Assessment Appeals Board reviews cases, and Proposition 8 allows automatic reductions when property values decline.

Q: What happens if I pay late? A: A 10% penalty applies immediately after delinquency dates, plus additional costs. Properties become tax-defaulted after five years of non-payment, potentially leading to tax sale.

Q: How can I pay my property taxes? A: Pay online at the Sonoma County Tax Collector website, by mail, or in person. Accept credit cards (with processing fees), electronic checks, or traditional checks.

Q: Why did my taxes increase more than 2%? A: While Proposition 13 limits base assessment increases to 2%, voter-approved bonds, new special assessments, or property improvements can increase your total bill beyond this cap.

Q: What triggers property reassessment? A: Sales, transfers between non-family members, new construction, and major improvements trigger reassessment. Parent-to-child transfers may qualify for continued low assessments under Proposition 19 rules.

Q: How do Mello-Roos taxes work? A: Community Facilities Districts (CFDs) in newer developments impose additional taxes for 20-40 years to fund infrastructure. These appear as separate line items on your tax bill and aren't subject to Proposition 13 limits.

Verified Sources

Backed by 10 Official Government Sources

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

01
Tax Doc
Property Tax Accounting Divisionsonomacounty.gov
02
Tax Doc
Tax Ratessonomacounty.gov
03
County
BOE Tax Rate Area Maps – Sonoma County 2025boe.ca.gov
04
Due Dates and Penaltiessonomacounty.gov
05
Tax Doc
Property Tax Frequently Asked Questionssonomacounty.gov
06
Important Datessonomacounty.gov
07
Homeowner's Exemptionsonomacounty.gov
08
Tax Doc
Property Tax Exemptionssonomacounty.gov
09
Exemptions and Assistance Programssonomacounty.gov
10
Tax Doc
Supplemental Property Taxessonomacounty.gov
All sources verified as of 2025 Tax Year

See the Full Picture of Your Home Costs

Property taxes are just one piece of homeownership. HonestCasa helps you understand your total monthly cost and explore safe ways to access your home equity.

Total Monthly Cost

Mortgage + taxes + insurance + HOA

Equity Growth

Track how your equity grows over time

Safe Equity Access

Options for projects or debt payoff

Run Your ScenarioTry Calculator

Free • No credit check • 2-minute estimate