Quick answer: Contra Costa property tax due dates for 2026 to 2027: the first installment of your secured property tax bill is due November 1, 2026 and becomes late after 5:00 p.m. on Thursday, December 10, 2026. The second installment is due February 1 and becomes late after April 10, and each late installment gets a 10% penalty.
Every fall, our phones light up with the same questions from clients in Lafayette, Orinda, Moraga, Richmond, and El Sobrante. "Did my tax bill come yet?" "Why did I get a second bill after I bought?" "Can I get my taxes lowered?" So here is a plain, local guide to what is due, when, and the few things that can actually save you money this year.
Contra Costa property tax due dates for 2026 to 2027
According to the Contra Costa County Treasurer-Tax Collector, the annual secured tax bill can be paid in two installments:
- 1st installment: due November 1, 2026. Late after 5:00 p.m. in person, or midnight online, on December 10, 2026. A 10% penalty is added after that.
- 2nd installment: due February 1, 2027. Late after April 10, 2027. A 10% penalty plus a $20 cost is added after that.
- Weekends and holidays: if a delinquency date lands on a weekend or holiday, it moves to the next business day.
- Paying both at once: you can pay the full year on or before December 10. The first installment has to be paid before the second.
The county accepts payments online through its Tax Portal, by phone at (925) 608-9500, by mail (they honor USPS postmarks), and in person at 625 Court Street in Martinez. Partial payments are not accepted, so pay the full amount on the coupon.
What if your bill never showed up?
Not getting a bill does not get you out of the penalty. The county says that if you have not received your secured bill by November 10, you should call the Tax Collector or look up your parcel online and print a copy. This happens a lot with recent buyers, because the bill can go to the previous owner.
Do you pay it, or does your lender?
If your mortgage has an impound (escrow) account, your lender usually pays the bill for you. It is still smart to log in to the county portal in December and confirm the payment posted. If you do not have an impound account, the bill is on you.
How property taxes work in California, in plain English
Under Proposition 13, the general property tax rate is capped at 1% of your home's assessed value, plus any voter-approved bonds and local assessments. That is why two similar homes on the same Orinda street can have very different bills.
Your assessed value is usually set when you buy. After that, it can only rise by the rate of inflation, and never more than 2% in a year, unless you sell or add new construction. So long-time owners in Lamorinda or North Richmond often pay far less than a buyer who just closed next door.
Just bought a home? Watch for the supplemental tax bill
This is the one that surprises buyers. When a home changes hands, the county reassesses it at the new purchase price. Because your regular bill was based on the seller's old value, the county sends a separate supplemental tax bill to cover the difference for the rest of the tax year.
- Supplemental bills are separate from your regular bill, and lenders often do not pay them from your impound account. Check with your lender.
- The county notes that new owners usually get a notice of supplemental assessment about 90 to 120 days after the deed records.
- Late supplemental installments get the same penalties as regular bills.
If you are still deciding whether to buy, factor the new tax amount into your monthly cost from day one. Our post on whether renting is cheaper than buying in Contra Costa County walks through the full monthly picture.
Three ways homeowners can lower their bill
1. File the homeowners' exemption
If you own and live in the home as your main residence on January 1, you can claim the homeowners' exemption. It takes $7,000 off your assessed value, which the county says saves about $70 a year. It is small, but it is free money. New owners have to file even if the seller already had it. The deadline for the full exemption is February 15, and a partial exemption is available if you file between February 16 and December 10.
2. Ask for a decline in value review (Prop 8) by November 30
If you bought near a peak and your home's market value as of January 1, 2026 is lower than its assessed value, you can ask the Assessor for an informal review. The county's Request for Value Review form asks for it back by November 30, and there is no fee. A formal appeal with the Assessment Appeals Board must be filed between July 2 and November 30. Either way, you still have to pay your taxes on time while a review is pending.
Not sure what your home is worth today? Our free home valuation is a good starting point before you file.
3. 55 or older? Know about Proposition 19
Prop 19 lets homeowners who are at least 55, or severely disabled, move their Prop 13 tax base to a replacement primary home anywhere in California. According to the California Board of Equalization, you need to buy the new home within two years of selling the old one (or the other way around), and each person can use it up to three times. If the new home costs more than the old one, part of the difference gets added to your tax base.
For a lot of our Lamorinda clients who want to downsize, this is the piece that makes a move pencil out. If that is you, read how to maximize your equity before your next move.
What this means if you are buying or selling now
- Sellers: property taxes are normally prorated in escrow. If you close before December 10 and the first installment is unpaid, escrow usually pays it from your proceeds. Ask your escrow officer.
- Buyers: budget for taxes based on your purchase price, not the seller's current bill, and set money aside for the supplemental bill.
- Everyone: property taxes, insurance, and HOA dues all add up. Our guide to the California insurance crisis covers the other big line item.
Frequently asked questions
When are Contra Costa County property taxes due in 2026?
The first installment is due November 1, 2026 and is late after December 10, 2026. The second installment is due February 1, 2027 and is late after April 10, 2027.
What is the penalty for paying Contra Costa property taxes late?
A late first installment gets a 10% penalty. A late second installment gets a 10% penalty plus a $20 cost. If taxes are still unpaid after June 30, the property becomes tax-defaulted and more fees and interest apply.
Why did I get a second property tax bill after buying my home?
That is the supplemental tax bill. The county reassesses a home when it sells and bills the new owner for the difference between the old and new assessed value for the rest of the tax year.
How much does the homeowners' exemption save in Contra Costa?
It removes $7,000 from your assessed value, which saves about $70 a year. File by February 15 for the full exemption.
Can I lower my property taxes if my home value dropped?
Yes. You can ask the Assessor for a free decline in value review (Prop 8) by November 30, or file a formal appeal between July 2 and November 30.
Can I keep my low property tax if I downsize in California?
If you are 55 or older, or severely disabled, Prop 19 lets you transfer your tax base to a replacement primary home anywhere in California, up to three times, as long as both moves happen within two years.
Thinking about a move in the East Bay?
Property taxes are one of the biggest numbers people forget when they plan a purchase or a sale. We are happy to run the math with you, whether you are looking at East Bay homes for sale, curious about El Sobrante or Richmond, or weighing a downsize in Lamorinda. Contact The Azagra Group and let's talk it through.
This post is general information, not tax or legal advice. Confirm your exact amounts and deadlines with the Contra Costa County Treasurer-Tax Collector and Assessor, or a tax professional.
