Table of content
- How Do You Perform a Contra Costa County Property Tax Lookup?
- What's on Your Contra Costa County Tax Bill?
- How Do You Contact the Contra Costa County Treasurer-Tax Collector?
- How Do You Pay Your Contra Costa County Property Taxes?
- When Are Contra Costa County Property Taxes Due, and What Are the Penalties?
- What Exemptions and Assessment Appeals Are Available Through the Contra Costa County Assessor?
- How Do You Update Your Mailing Address With Contra Costa County?
- How Can the Renée White Team Help Contra Costa County Homeowners?
- What's the Easiest Way to Handle Your Contra Costa County Property Tax Lookup?
- Frequently Asked Questions
KEY TAKEAWAYS
- How to complete a Contra Costa County property tax lookup by address or Assessor’s Parcel Number (APN)
- Who to contact at the Treasurer-Tax Collector and the Assessor’s Office with questions
- The two annual instalment due dates, and what happens if a payment is missed
- Whether monthly payment plans exist for Contra Costa County property taxes
- How to update your mailing address, request an informal review, file a formal appeal, or get guidance from the Renée White Team along the way
If you own property in Contra Costa County, you will eventually need to do a property tax lookup: whether you just bought a home, misplaced a notice, or want to confirm what you owe before a deadline. Once you know where to go, a Contra Costa County property tax lookup is a straightforward process.
This guide covers how to find your bill, how to read it, who to contact when something looks wrong, and every way to pay, including whether monthly payments are an option.
Property taxes fund local schools, roads, libraries, and emergency services. Staying on top of your bill is good for your finances and for the community. It is something the Renée White Team keeps front of mind when guiding Contra Costa homeowners and buyers through every stage of ownership.
How Do You Perform a Contra Costa County Property Tax Lookup?
Search by property address or Assessor’s Parcel Number (APN). Both appear on your deed and any previous tax bill. The county’s official Tax Lookup Portal, run by the Treasurer-Tax Collector, is the right place to start.
Once you search, the portal shows the total amount due, a breakdown of each instalment, payment status, and prior payment history. Balances update at least weekly, so a recent payment may not yet be reflected.
Prefer to call or visit in person? The Treasurer-Tax Collector’s office can help. For historical records or parcel maps, the Assessor’s Office handles that separately from your current-year bill.
What’s on Your Contra Costa County Tax Bill?
Your tax bill is based on the assessed value the Assessor places on your property as of 1 January each year, known as the lien date. The Assessor records this in the assessment roll, a county-wide list of every taxable property with its ownership details and assessed value.
Want to see what that looks like in dollars? The Contra Costa County Property Tax Calculator gives a quick estimate, and our guide to Contra Costa property tax covers the county’s rates and rules in more detail.
Secured vs. Supplemental Tax Bills
Most homeowners receive a secured tax bill each year. If you recently bought a home or completed new construction, you may also get a supplemental bill on top of that. It is easy to miss if you are only expecting the standard one.
| Secured Tax Bill | Supplemental Tax Bill | |
| What it covers | Homes, vacant land, and other real property | The difference between the prior assessed value and the new value |
| When it’s issued | Annually, for every taxable property | When ownership changes, or new construction is completed |
| Who receives it | All property owners | Recent buyers and those who have built or extended |
| Relation to your regular bill | The standard annual bill | Issued separately, in addition to the regular bill |
For more on how supplemental bills are calculated and when refunds apply, see our guide to supplemental property tax in California.
What Information Appears on the Bill?
Your bill will show:
- Your Assessor’s Parcel Number (APN)
- The assessed value of your property
- Any exemptions applied
- The total amount owing
- The due date for each instalment
If anything looks wrong, contact the Assessor’s Office. They maintain the assessment roll that drives everything else on your bill.
How Do You Contact the Contra Costa County Treasurer-Tax Collector?
The Treasurer-Tax Collector’s office is at 625 Court Street, Room 100, Martinez, CA 94553.
- Phone: (925) 608-9500
- Office hours: Monday to Friday, 8:00 a.m. to 5:00 p.m., excluding public holidays
- Accessibility: call 711 for hearing or speech relay assistance
- Mail: same Martinez, CA 94553 address, attention Treasurer-Tax Collector
Keep your mailing address current, as notices, bills, and reminders go to whatever is on file. If you own or are researching a property in Martinez specifically, our guide to Martinez property tax covers local rates and rules.
How Do You Pay Your Contra Costa County Property Taxes?
- E-check: no service fee, the cheapest online option
- Credit or debit card: 2.5% fee, minimum $3.50, charged by a third-party processor
- In person: 625 Court Street, Room 100, Martinez, CA 94553, during office hours
- By phone: the county’s automated line handles payments after hours
- By mail: send a cheque with the payment coupon to the Treasurer-Tax Collector
Each payment must cover the full amount on the coupon. Partial payments are not accepted. If a cheque bounces, a fee of up to $85 applies on top of any penalty, so make sure funds are available first.
Setting Up Monthly Payments
The county bills twice a year, not monthly. But if you prefer to spread the cost, a county-recognised private platform lets homeowners set up equal monthly payments on their behalf, using card or bank transfer at lower fees than the county’s direct card rate. As it is a private service, read the terms before signing up.
When Are Contra Costa County Property Taxes Due, and What Are the Penalties?
- First instalment: due 1 November, penalty applies after 5:00 p.m. on 10 December
- Second instalment: due 1 February, penalty applies after 5:00 p.m. on 10 April
Both instalments can be paid together when the first comes due, and some homeowners find this easier than tracking two dates. A 10% penalty is added to any late instalment, with an additional administrative cost on the second if it goes unpaid.
The county offers free e-billing reminders sent roughly two weeks before each deadline.
What Exemptions and Assessment Appeals Are Available Through the Contra Costa County Assessor?
The Assessor sets your assessed value, maintains parcel maps and ownership records, and fields questions about how properties are valued. If your assessment looks too high, here is what to do.
Homeowner’s Exemption
If you live in the home you own, you can apply for the Homeowner’s Exemption. It reduces your assessed value by $7,000, a small saving but free and automatic once you file. It renews each year as long as the property stays your primary residence. See who qualifies for property tax exemption in California for the full picture.
Senior and Parcel Tax Exemptions
Some line items on your bill carry an asterisk, which means a senior exemption may apply. Call the number listed next to that line item to find out. If you are 55 or older or have a severe disability, you may also be able to transfer your existing assessed value to a new home under Prop 19. Our guide on transferring your property tax base under Prop 19 explains the rules.
Disputing an Assessment
Start with an informal review. Call the Assessor’s Office at (925) 313-7400. Many issues are resolved here without any formal paperwork. If not, file a formal appeal with the County Assessment Appeals Board by 30 November, or within 60 days of receiving an assessment notice. Keep paying your bill while the appeal is being reviewed. Disputing the amount does not pause your payment obligation.
A 2023 report from the Institute on Taxation and Economic Policy found that accessible, well-publicised exemption programmes are among the most effective ways to protect long-term homeowners from rising assessments. Check every year whether you are claiming everything you are entitled to.
Property tax rates also differ significantly across the US, as shown in the Lincoln Institute of Land Policy’s 50-State Property Tax Comparison Study. Your county assessor and tax collector are always the most accurate source for what applies to your property.
How Do You Update Your Mailing Address With Contra Costa County?
Your bill, e-billing notices, and assessment letters go to whatever address the county has on file. If it is wrong, you may miss a deadline and face a penalty, even though the bill was sent.
Contact the Assessor’s Office to update it. Changing your address with your mortgage lender or title company does not update it with the county. Those are separate records.
How Can the Renée White Team Help Contra Costa County Homeowners?
Property taxes are one part of the cost of owning a home in Contra Costa County. Here is what the Renée White Team brings to the rest of that conversation:
- Local expertise backed by results: The Renée White Team is the #1 real estate team in Contra Costa County by units sold, with 1,600+ transactions and $1.4B in career sales across 21+ years.
- Full cost of ownership: The team helps buyers understand every cost before making an offer, with no surprises at closing.
- Up-to-date market knowledge: The Contra Costa Housing Market guide covers current prices, trends, and forecasts.
- Help for buyers and sellers: Whether purchasing, listing, or working through your current costs, the Renée White Team is ready.
What’s the Easiest Way to Handle Your Contra Costa County Property Tax Lookup?
Search by address or APN at the county’s Tax Lookup Portal, know your two deadlines, and check each year whether you qualify for an exemption. Keep your mailing address current with the Assessor, opt in to free e-billing reminders, and you will avoid most of the common problems.
If you are buying in Contra Costa County and want a clear picture of what your tax bill will look like before you make an offer, the Renée White Team has been helping buyers and homeowners across Walnut Creek, Concord, Danville, Lafayette, Martinez, Orinda, Alamo, and Clayton for more than 21 years. Our guides on closing costs in Contra Costa County and the first-time home buyer process in Walnut Creek are good starting points. Reach out to the team for advice specific to your situation.
