Contra Costa County Property Tax Guide for Homeowners and Sellers

Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team. Figures come from the county’s Tax Collector pamphlet for 2024-2025, listed under Sources; confirm current amounts on your own bill.

Contra Costa County secured property taxes are delinquent after December 10 (first installment) and April 10 (second installment), with a 10 percent penalty on each and an added $20 cost on the April installment. Taxes unpaid after 5 p.m. on June 30 go into default, with a $15 redemption fee and 1.5 percent interest each month. When you sell, unpaid taxes are paid from your proceeds at closing.

Contra Costa County property tax at a glance

First installment	Due November 1; delinquent December 10; 10% penalty
Second installment	Due February 1; delinquent April 10; 10% penalty plus a $20 cost
Default	After 5 p.m. June 30: $15 redemption fee plus 1.5% per month
Payment plan	Five-year plan; must be started by June 30
Power of sale	After five years unpaid; notices go out in May
Supplemental bills	Same penalties as secured bills; due on receipt
Pay online	www.cctax.us: e-check free, card fee 2.5% (minimum $3.50)
In person	625 Court Street, Room 100, Martinez, CA 94553
By mail	P.O. Box 631, Martinez, CA 94553
Phone	(925) 608-9500, Monday to Friday, 8 a.m. to 5 p.m.

Due dates for Contra Costa County property taxes

The county’s pamphlet repeats the familiar California calendar: bills are due November 1 and February 1, and they turn delinquent on December 10 and April 10. The pamphlet is specific about partial payments: the county does not accept them, so each installment must be paid in full. That matters if you plan to chip away at a bill. Paying half of the first installment on December 9 leaves the whole installment treated as late.

The second installment is the costly one to miss. Its 10 percent penalty comes with a $20 cost, so a $2,500 installment paid late would cost $270 extra, versus $250 for a late first installment.

How to pay in Contra Costa County

• Online at www.cctax.us. E-check carries no fee. Card payments are charged 2.5 percent, with a $3.50 minimum.
• By phone through the automated line at (925) 608-9500.
• In person at the Tax Collector’s counter, 625 Court Street, Room 100, in Martinez.
• By mail to P.O. Box 631, Martinez, CA 94553.

For questions about the value of your home or the homeowner’s exemption, the Assessor’s number is (925) 313-7400, and the exemption desk is at (925) 313-7481.

What happens if you don’t pay

Once an installment is delinquent, the penalty attaches. Taxes still unpaid after 5 p.m. on June 30 are in default. The county adds a $15 redemption fee and 1.5 percent a month on the balance, and it keeps adding that charge until the account is redeemed.

There is a structured way to catch up: a five-year payment plan. The deadline to start one is June 30, and the plan requires current taxes to be paid as they come due.

After five years of non-payment, the property becomes subject to the power of sale, and the Tax Collector mails notices to affected owners in May. Our tax-defaulted auction guide describes what a sale looks like, and our foreclosure report covers mortgage default.

Supplemental tax bills

When a home sells or new construction is completed, the Assessor updates the value and a supplemental bill follows. Contra Costa’s pamphlet says supplemental bills carry the same penalties as secured bills and are due when received. That differs from the November and February rhythm, so buyers should set money aside for it after closing, and sellers should know the buyer will see it.

Estimate the transfer tax on your Contra Costa County sale

The calculator applies the statewide county rate of $0.55 per $500. Several Contra Costa cities may charge a city tax too, and this estimate does not include one, so ask escrow for the total.

How to sell a house in Contra Costa County when you owe property taxes

Delinquent property taxes are a lien, and a lien does not stop a sale. It only has to be paid at closing.

1. Request the amount due. Call the Tax Collector at (925) 608-9500 or check www.cctax.us. Ask for the figure on your intended closing date, because monthly interest changes it.
2. Remember that partial payments are refused. You cannot pay down the lien in pieces before closing, so plan for escrow to pay it in full.
3. Compare timelines. If taxes are about to go into default on June 30, a fast cash close can stop the monthly charge from starting.
4. Choose your buyer. Cash buyers purchase as-is; traditional buyers need inspections, appraisals and loan approval.

We buy houses throughout the county. See our Contra Costa County page, plus local pages for Richmond, Concord and Antioch. For market context, read the 2026 Contra Costa housing report.

Not sure what your house would net? Call (424) 435-2326 or request a cash offer. There is no cost and no obligation.

Contra Costa County property tax FAQ

When are Contra Costa County property taxes delinquent?

The first installment is delinquent after December 10 and the second after April 10.

What is the penalty in Contra Costa County?

10 percent on either installment, plus a $20 cost on the second.

Can I make partial payments?

No. The county’s pamphlet says it does not accept partial payments.

Is there a payment plan for defaulted taxes in Contra Costa County?

Yes, a five-year payment plan, which must be started by June 30.

Can I sell a Contra Costa County house with unpaid property taxes?

Yes. The balance is paid from your proceeds through escrow at closing.

Sources

• Contra Costa County Treasurer-Tax Collector: Tax Collector Pamphlet 2024-2025, published on contracosta.ca.gov
• Sacramento County Clerk-Recorder fee schedule (statutory $0.55 per $500 under Revenue and Taxation Code 11911)

This guide is general information, not tax or legal advice. Dates, fees and rates can change; confirm your balance with the Contra Costa County Tax Collector.