Whether you just closed on a home in Concord or have owned in Walnut Creek for years, understanding how Contra Costa County property taxes work can save you money and prevent surprise bills. This guide covers the current 2025-2026 tax rates, due dates, city-level breakdowns, how to pay online, and what to do if you think your assessment is too high.
What Are Property Taxes and How Are They Used?
Property taxes are annual charges levied by local government on real estate owners. In Contra Costa County, those revenues fund public schools, fire and police services, road maintenance, libraries, and other community infrastructure. For most homeowners, property taxes are one of the larger recurring costs of ownership alongside the mortgage payment itself.
How Much Is Property Tax in Contra Costa County?
California’s Proposition 13 sets the base property tax rate at 1% of a property’s assessed value statewide. On top of that base rate, Contra Costa County and its cities add voter-approved local assessments and bond measures. The result is an effective rate that varies by location.
For most properties in Contra Costa County during the 2025-2026 assessment year, the effective property tax rate falls between 1.2% and 1.5% of assessed value, depending on the city and applicable special assessments.
The county calculates your tax bill by multiplying your property’s assessed value by the applicable rate for your tax rate area (TRA). Your TRA is determined by your address and reflects which special districts, school bonds, and local measures apply to your property.
2025-2026 Property Tax Rates by City in Contra Costa County
Effective tax rates vary across Contra Costa cities because each area carries different voter-approved bond measures and special assessments. The figures below represent estimated effective rates for typical residential properties in each city. Your actual rate depends on your specific tax rate area.
| CITY | ESTIMATED EFFECTIVE TAX RATE | NOTES |
|---|---|---|
| Concord | ~1.30% | Includes Mt. Diablo USD and city bonds |
| Walnut Creek | ~1.25% | Acalanes USD area; fewer special assessments |
| Antioch | ~1.45% | Antioch USD bonds; higher special district levies |
| Richmond | ~1.50% | West Contra Costa USD; multiple bond measures |
| San Ramon | ~1.35% | San Ramon Valley USD; strong school bond base |
| Pittsburg | ~1.45% | Mt. Diablo USD; city and infrastructure bonds |
| Pleasant Hill | ~1.30% | Mt. Diablo USD; moderate bond load |
| Brentwood | ~1.40% | Liberty USD; newer infrastructure bonds |
| Danville | ~1.25% | San Ramon Valley USD; lower overall levy |
| Hercules | ~1.35% | West Contra Costa USD; city-specific bonds |
| Martinez | ~1.30% | County seat; Mt. Diablo USD bonds |
| El Cerrito | ~1.50% | West Contra Costa USD; BART and school bonds |
To find the exact rate for your property, use the Contra Costa County Assessor’s property lookup tool and enter your parcel number or address.
When Are Contra Costa Property Taxes Due?
Property taxes in Contra Costa County are billed annually but paid in two installments.
| INSTALLMENT | DUE DATE | DELINQUENT AFTER |
|---|---|---|
| First Installment | November 1 | December 10 |
| Second Installment | February 1 | April 10 |
Missing the December 10 or April 10 deadlines triggers a 10% penalty on the unpaid amount. If the second installment remains unpaid after June 30, the property may be subject to a tax lien. Not receiving a bill does not exempt you from these deadlines or penalties.
If you escrow your taxes through your mortgage, your lender handles these payments automatically from your monthly escrow deposit. Check your annual escrow analysis to confirm the correct amount is being collected.
How to Pay Contra Costa Property Taxes Online
The Contra Costa County Treasurer-Tax Collector’s Office accepts online payments through its official portal. You can pay by credit card, debit card, or e-check.
To pay online:
- Visit www.cctax.us
- Search for your property using your parcel number, address, or bill number
- Select the installment you want to pay
- Choose your payment method and complete the transaction
Keep your confirmation number. A convenience fee applies to credit and debit card payments; e-check payments are typically lower cost.
You can also pay by mail or in person at the Treasurer-Tax Collector’s Office located at 625 Court Street, Room 100, Martinez, CA 94553. [FLAG: Confirm current office address before publishing.]
What Are Supplemental Property Taxes?
When you purchase a home in Contra Costa County or complete new construction or major improvements, the county reassesses your property at its new market value. If the new assessed value is higher than the previous one, you’ll receive a supplemental tax bill for the difference.
Supplemental taxes are prorated based on how many months remain in the fiscal year (July 1 to June 30) from the date of ownership change or project completion. If you buy a home in January, for example, you’ll owe supplemental taxes covering roughly six months of the reassessment difference.
Supplemental bills are separate from your regular property tax bill and arrive on their own schedule. New homeowners sometimes miss them because they arrive months after closing. Watch for them and factor the cost into your budget.
How to Appeal Your Property Tax Assessment in Contra Costa County
If you believe your property has been assessed at more than its fair market value, you have the right to appeal. Many homeowners skip this step without realizing how straightforward the process is.
When to Consider an Appeal
An appeal makes sense when your property’s assessed value is higher than what comparable homes in your area actually sold for. This can happen after a rapid market correction, if the assessor used outdated data, or if there are property-specific issues (condition, access, easements) that weren’t accounted for.
How to File an Appeal
- Get your current assessed value. Find it on your property tax bill or through the Contra Costa County Assessor’s website.
- Gather comparable sales data. Pull recent sales of similar homes in your neighborhood to support your argument that the assessed value is too high.
- File an Application for Changed Assessment with the Contra Costa County Assessment Appeals Board. The standard filing window is July 2 through November 30. [FLAG: Confirm the 2025-2026 filing deadline with the Assessment Appeals Board before publishing.]
- Attend your hearing. You’ll present your evidence to the board, and they will issue a decision.
If your appeal is successful, your assessed value will be reduced and you’ll receive a refund for any overpaid taxes. There is no penalty for filing an unsuccessful appeal.
For forms and filing instructions, visit the Contra Costa County Assessment Appeals Board.
Proposition 13 and Your Annual Tax Cap
Under California’s Proposition 13, the assessed value of your property can increase by no more than 2% per year as long as you own it and do not trigger a reassessment event. Reassessment events include a sale, transfer of ownership, or completion of new construction.
This cap is one of the most significant protections California homeowners have. It means a homeowner who has owned their property for 20 years may be paying taxes on an assessed value far below current market value, which is entirely legal and by design.
When you purchase a home, the assessed value resets to the purchase price. From that point forward, your annual increases are capped at 2% until the next qualifying change in ownership.
Frequently Asked Questions
What is the property tax rate in Contra Costa County?
The base rate is 1% under Proposition 13. With voter-approved bonds and local assessments added, most Contra Costa homeowners pay an effective rate between 1.2% and 1.5% depending on their city and tax rate area.
When are Contra Costa County property taxes due?
The first installment is due November 1 and becomes delinquent after December 10. The second installment is due February 1 and becomes delinquent after April 10.
How do I pay Contra Costa property taxes online?
Visit www.cctax.us, search for your property, and pay by credit card, debit card, or e-check. A convenience fee applies to card payments.
How do I appeal my property tax assessment?
File an Application for Changed Assessment with the Contra Costa County Assessment Appeals Board between July 2 and November 30. Bring comparable sales data to support your case.
What is a supplemental property tax?
A one-time bill triggered when your property is reassessed due to a purchase, ownership change, or new construction. It covers the difference between the old and new assessed values, prorated for the months remaining in the fiscal year.
Are property tax increases limited in California?
Yes. Proposition 13 caps annual assessed value increases at 2% per year unless there is a change in ownership or new construction.
Want to Learn More?
Property taxes are one of the most significant ongoing costs of homeownership in California, and Contra Costa County is no exception. Understanding your rate, your exemptions, and your right to appeal can make a real difference in what you pay year over year. At JVM Lending, we help Bay Area homebuyers and homeowners understand how property taxes fit into their mortgage payments and long-term financial plans. Whether you are buying in Concord, refinancing in Walnut Creek, or exploring your options anywhere in Contra Costa County, we are here to help.
Contact JVM Lending today for a free consultation.
Please note: The information in this post is for educational purposes only. JVM Lending is not a tax professional or financial advisor. Property tax laws can be complex and vary by location. Consult a certified tax professional for personalized guidance. If you need a referral, contact us and we’ll connect you with a trusted professional in our network.
