Rate Breakdown

Property taxes in Contra Costa County are calculated by multiplying the assessed value (minus exemptions) by the total local millage rate.

How Property Tax Works in Contra Costa County

Contra Costa County calculates property taxes based on the assessed value of each parcel and the applicable millage rates set by local taxing entities. The County Assessor’s Office determines the assessed value on the acquisition date (the “base year value”) and then adjusts it annually for inflation using the California Consumer Price Index, capping increases at 2 % per year under Proposition 13. The assessed value becomes the foundation for the tax bill.

Millage rates are expressed in dollars per $1,000 of assessed value. In the 2024‑2025 fiscal year, the combined general tax rate for most residential properties in Contra Costa County is approximately 1.21 % (or 1,210 mills). This rate includes the County’s 1 % general fund, the school district’s rate, and additional special district levies such as fire, water, and community services districts. The exact figure can vary by address because each special district sets its own millage.

To estimate your annual tax, multiply the assessed value by the total millage rate and divide by 1,000. For example, a home assessed at $600,000 with a combined rate of 1,210 mills would owe roughly $726 in property tax for the year.

Available Exemptions

California law provides several exemptions that can reduce the taxable portion of your property’s assessed value. In Contra Costa County, the most common are:

• Homestead Exemption (Owner‑Occupied): The first $7,000 of assessed value for owner‑occupied residential property is exempt, lowering the tax bill by about $8.50 per $1,000 of millage.
• Senior Citizen Exemption: Residents age 62 or older may qualify for a $7,000 exemption (same amount as the homestead) plus an additional $7,000 exemption if the senior’s income is below a state‑set threshold.
• Disability Exemption: Qualified persons with a permanent disability can receive a $7,000 exemption, with a possible second $7,000 exemption for low‑income individuals.
• Veteran Exemption: Disabled veterans (or their surviving spouses) may claim a $7,000 exemption, and a second $7,000 exemption is available for those with a 100 % service‑connected disability.

All exemptions are applied to the assessed value before the millage calculation, resulting in a lower tax bill. Applications are submitted to the Contra Costa County Assessor’s Office, typically by March 1 of the tax year.

Payment Schedule & Deadlines

Contra Costa County follows the state‑mandated two‑installment schedule for property tax payments:

• First Installment: Due November 1, with a grace period until December 10. Paying by the due date avoids a 10 % penalty.
• Second Installment: Due February 1, with a grace period until April 10. The same 10 % penalty applies for late payments.

If either installment is not paid by the end of its grace period, the county adds a 10 % penalty and a 10 % interest charge on the overdue amount. Persistent delinquency can lead to tax‑sale procedures, including a tax lien and eventual foreclosure. Many taxpayers choose to pre‑pay the entire annual amount on or before November 1 to simplify budgeting and avoid penalties.

Appealing Your Assessment

If you believe your property’s assessed value is inaccurate, you have the right to appeal. The process in Contra Costa County proceeds as follows:

• File a Formal Protest: Submit a written protest to the County Assessor’s Office by July 2 of the assessment year. Include supporting evidence such as recent comparable sales, independent appraisals, or error corrections.
• Assessment Appeal Board (AAB) Hearing: If the Assessor’s Office does not adjust the value to your satisfaction, the case moves to the AAB. A hearing is scheduled, and you may present testimony and documents in person or via video conference.
• Decision & Further Review: The AAB issues a written decision, usually within 30 days of the hearing. If still dissatisfied, you may petition the Superior Court of California, County of Contra Costa, within 60 days of the AAB decision.

Preparing a strong appeal hinges on accurate, recent market data and clear documentation of any errors. Many homeowners consult a qualified real‑estate appraiser or property tax attorney to improve their chances of a successful outcome.