Contra Costa County property tax: rates, bills, and appeals explained

Last updated 2026-07-09

How does Contra Costa County property tax work?

Contra Costa property tax has two parts: a 1% base levy set by Proposition 13, plus a stack of smaller voter-approved charges (school bonds, community college bonds, library and flood control assessments) layered on top. Voters passed Prop 13 in 1978. It locked the base rate at 1% of assessed value and capped annual increases in that value at 2% a year, no matter what the market does. ^[1]

In most Contra Costa cities, those add-ons push the effective rate to somewhere between 1.1% and 1.25% of assessed value. Your exact rate depends on which taxing rate area (TRA) your parcel sits in, because every school district and special assessment district draws its own boundary.

Three separate offices touch your bill. The Assessor sets the assessed value. The Auditor-Controller applies the tax rates. The Tax Collector mails the bill and takes the money. ^[2]

That split matters the moment you have a problem. A fight about your assessed value goes to the Assessor, and if that stalls, to the Assessment Appeals Board. A fight about the arithmetic on your bill goes to the Auditor-Controller. Send your complaint to the wrong office and you lose weeks.

For context on how this compares to other California counties, the Santa Clara County property tax system runs on the same Prop 13 foundation, though bond add-ons differ by district. The LA County property tax framework is identical in structure, just at a much larger scale.

What is the property tax rate in Contra Costa County?

The California Constitution sets the base rate at 1% of full cash value. ^[1] On top of that, every parcel carries whatever voter-approved bonds apply in its TRA, and Contra Costa has more than 400 of those areas. Most homeowners land between 1.09% and 1.25% total.

Here is a representative sample of total rates (base plus bonds) for common cities, drawn from the county's published 2023 to 24 tax rate book: ^[3]

City / Area	Approximate TRA Total Rate
Concord (MDUSD zone)	~1.17%
Richmond (WCCUSD zone)	~1.22%
Walnut Creek (MDUSD zone)	~1.11%
Antioch (AUSD zone)	~1.20%
Brentwood (BOUSD zone)	~1.18%
Danville (SRVUSD zone)	~1.09%
Unincorporated (varies)	~1.10 to 1.25%

Treat those as ballpark figures. Your exact rate lives in the county's TRA lookup tool on the Auditor-Controller's website. ^[3] To find your TRA number, look at the upper-right corner of your annual tax bill.

One thing worth knowing: Mello-Roos Community Facilities Districts (CFDs) can add a hefty flat charge on top of the ad valorem rate. New construction communities in East County, especially Brentwood and Discovery Bay, often carry Mello-Roos levies of $1,000 to $3,000 a year or more. That charge never shows up in the percentage rate. It appears as a fixed dollar amount on your bill, and it can double what a percentage rate alone would suggest.

How is my assessed value calculated in Contra Costa?

Your assessed value is almost never your current market value, unless you bought or built recently. Under Proposition 13, the county sets your base year value at the purchase price the year you acquired the property (or its fair market value if you built it). ^[1] After that, the Assessor can raise it by no more than 2% a year, indexed to the California Consumer Price Index when the CPI runs lower.

Run the math on a real example. A house bought in 2005 for $480,000 has a 2024 assessed value of at most $480,000 times 1.02 to the 19th power, which works out to roughly $684,000, even if the house now sells for $1.1 million. The owner pays tax on $684,000, not on market value. That gap is the whole point of Prop 13 for long-term owners.

The other side of that coin hurts. If you bought in 2022 near the top and values have since slipped, you may be assessed higher than the house is worth today. That is a live problem in parts of Contra Costa right now, and it is exactly when a formal appeal earns its keep.

The Assessor also reviews value at any change of ownership or new construction. ^[4] A full reassessment to current market value happens at those trigger events. New construction gets a partial reassessment, meaning the new addition gets valued, not the rest of the house. When those events happen, the office mails a Notice of Supplemental Assessment. That notice carries its own appeal deadline, separate from the regular annual roll, and people miss it constantly.

When are Contra Costa County property taxes due?

California property tax bills cover a fiscal year that runs July 1 through June 30, and the Tax Collector mails the annual bill in October. ^[5] The first installment is due November 1. The second is due February 1. But the dates that actually cost you money are the delinquency dates: December 10 and April 10.

Installment	Covers	Due Date	Delinquent After
1st installment	July 1 to Dec 31	November 1	December 10 (10% penalty)
2nd installment	Jan 1 to June 30	February 1	April 10 (10% penalty + $10 fee)

Burn December 10 and April 10 into memory. Miss either by a single day and you owe a 10% penalty on that installment. ^[5] If a bill stays fully unpaid by June 30 of the fiscal year, the property enters tax default status and starts racking up redemption penalties at 1.5% per month.

The county takes payments online, by mail, or in person at the Tax Collector's office at 625 Court Street in Martinez. The postmark counts for mailed payments, so when April 10 lands on a weekend, the next business day becomes your real deadline.

Here is the trap that catches careful people: if you refinanced or your lender changed, your impound account can lag. Confirm your lender actually paid by checking the Tax Collector's online portal before the delinquency date. ^[5] Impound errors happen more than anyone expects, and the penalty lands on the property owner, not the lender.

What property tax exemptions are available in Contra Costa County?

California runs several exemptions through the county. These are the ones homeowners should know:

Homeowners' Exemption: Cuts the assessed value of your principal residence by $7,000, which saves roughly $70 a year at the 1% base rate. Small, but free, and it renews automatically as long as you stay in the home. File once with the Assessor's office by February 15 of the first year you qualify. ^[6]

Disabled Veterans' Exemption: Veterans with a service-connected disability rating may qualify for an exemption of $100,000 to $150,000 off assessed value, with the higher figure reserved for low-income households. Surviving spouses may also qualify. ^[6]

Senior Citizens' Property Tax Postponement: This one is state-run, not county-run. It lets qualifying seniors 62 or older with household income under $45,810 defer property taxes at 7% annual interest until the property sells. The State Controller's office runs it. ^[7]

Proposition 19 Parent-Child and Grandparent-Grandchild Transfers: Under Prop 19 (effective February 16, 2021), a child who inherits a parent's primary residence keeps the parent's lower assessed value only by moving in as their own primary residence within one year, and only up to $1 million above the parent's assessed value. ^[8] This replaced a much broader pre-2021 exclusion. If you inherited a property after February 2021 and the Assessor reassessed it to full market value, that was probably correct under current law.

Proposition 19 Base Year Value Transfers (formerly Prop 60/90): Homeowners 55 or older can carry their existing base year value to a replacement residence anywhere in California, even one worth more, with an upward adjustment. ^[8] You can do this three times in your lifetime.

Church, nonprofit, and welfare exemptions run through the Assessor's office too, most of them on a February 15 annual filing deadline.

How do I appeal my Contra Costa County property tax assessment?

You appeal to the Contra Costa County Assessment Appeals Board (AAB), an independent three-member body that hears disputes between owners and the Assessor. ^[9] The regular filing window opens July 2 and closes November 30 of the same year the roll is published. That November 30 deadline is hard. Miss it and you wait a full year. For supplemental assessments (from a purchase or new construction), you get 60 days from the date on the Notice of Supplemental Assessment.

The filing fee is $30 for most residential properties. You file an Application for Changed Assessment with the Clerk of the Board, and the county's portal allows online filing. ^[9]

Here is what the AAB actually weighs. You have to show that your assessed value as of January 1 of the tax year topped the property's fair market value on that same date. That means comparable sales evidence: real sales of similar homes in your neighborhood that closed around that date at prices below your assessed value. The burden of proof sits on you.

Good evidence has a shape to it. Three to six comparable sales from the six months before and six months after the lien date. Properties close to yours in size, age, condition, and location. A simple adjustment grid showing how each comp stacks up against your house. The county appraiser uses the same method, so match it.

For a DIY approach to building that file, the TaxFightBack appeal kit walks you through comp selection and the adjustment grid step by step, so you walk into a hearing with a professional-grade case and keep the 30 to 50% of your savings a contingency firm would take.

At the hearing, you and an Assessor's staff appraiser each present. The board asks questions and issues a decision, usually within two weeks. Win, and the county refunds the overpayment plus interest at 3% a year under California Revenue and Taxation Code Section 5151. ^[10]

What is the appeal deadline for Contra Costa County?

November 30. That is the last day to file an Application for Changed Assessment with the Assessment Appeals Board Clerk for the current assessment year. ^[9] Nothing else in this process is as unforgiving.

Filing opens July 2 each year, the first day after the Assessor publishes the assessment roll. You do not need to wait for your October tax bill. Plenty of people file in July or August once they review the roll online.

Supplemental assessments follow their own clock. If you bought, finished a major renovation, or took ownership through a transfer, your deadline is 60 days from the mailing date printed on the Notice of Supplemental Assessment, not November 30. These slip past people because the notice arrives separately from the regular tax bill.

One caution: the AAB office closes early on November 30 in some years. Confirm the exact closing time with the Clerk of the Board at (925) 655-2000. Online filing, where available, takes that risk off the table.

Miss the deadline and you almost always wait a year. California courts treat these deadlines as jurisdictional, meaning judges generally cannot excuse a late filing no matter how sympathetic the reason.

How do I pay my Contra Costa County property tax bill online?

The Contra Costa County Tax Collector takes online payments through its official portal at cccounty.us/taxcollector. ^[5] You can pay by eCheck at no fee, or by debit or credit card, though credit cards carry a convenience fee, currently around 2.34% of the payment amount. On a $6,000 bill, that fee runs about $140, so use the eCheck option unless you have a reason not to.

For online or phone payments, you need your Assessor's parcel number (APN), which is printed on your tax bill. The portal also shows your current balance, payment history, and delinquency status by APN.

Bank bill-pay works differently. It counts as a mailed payment, so allow 7 to 10 business days for the check to reach the county. Do not cut it close. If you are inside two weeks of a delinquency date, pay through the online portal instead.

For a broader look at how counties handle online payments and where they trip people up, the online tax payment for property guide covers the common pitfalls across different county systems.

What happens if I disagree with the Assessment Appeals Board's decision?

If the AAB rules against you, your options narrow, but they do not vanish. You have three real paths, and only one of them is worth it for most homeowners.

First, within 90 days of the board's decision, you can file a petition for rehearing with the AAB itself. This is rare and the bar sits high. You need new evidence or a genuine procedural error, more than disappointment with the outcome.

Second, you can file a claim for refund under California Revenue and Taxation Code Section 5097 within four years of the date you paid the tax, pay under protest, then sue the county in Superior Court. ^[10] This costs real money in legal fees and rarely pencils out for a single-family home unless the disputed assessment is very large.

Third, and this is the one I would reach for, you refile next year if your property's market value genuinely dropped. Nothing stops annual appeals. Some owners in fast-falling markets win in consecutive years.

The honest lesson: bring your strongest case the first time. A clean, well-documented comp package settles most residential appeals at or before the hearing. The AAB's own numbers show a meaningful share of cases resolve by stipulation with the Assessor's office before any formal hearing date, and that share climbs when the applicant's evidence is solid.

How does Contra Costa County property tax compare to other California counties and national rates?

Every California county runs on Proposition 13, so the base mechanics are identical statewide. The differences come down to local bond measures.

Across California, the average effective property tax rate sits around 0.75 to 0.80% of market value, not assessed value, because Prop 13's caps keep most long-held properties assessed well below what they would sell for. ^[11] Contra Costa's effective rate as a share of actual market value falls in that same band.

Against other major California counties, Contra Costa's combined ad valorem plus bond rates track close to Alameda County (often 1.1 to 1.3%), sit above most rural counties, and run below some heavily bonded South Bay districts.

Nationally, Contra Costa looks cheap. California's effective property tax rate as a share of home value runs roughly 0.75%, which puts the state in the lower third nationwide, based on U.S. Census Bureau American Community Survey data. ^[12] Texas, by contrast, runs effective rates of 1.6 to 1.8% in most metro counties. Owners in states without an assessment cap pay far more as a share of what their homes are actually worth.

For a sense of how tax burden works under very different rules, compare Hennepin County property tax in Minnesota or Maricopa property tax in Arizona, both of which operate without Prop 13's assessment protections.

Are there any Contra Costa County property tax relief programs for seniors or low-income owners?

Yes, a handful of programs go beyond the standard exemptions, and one of them is underused.

The California Property Tax Postponement Program lets qualifying seniors (62 or older), blind, or disabled homeowners postpone current-year property taxes. You need the property to be your primary residence, household income of $45,810 or less, and at least 40% equity in the home. The State Controller's office runs the program and accepts applications from October 1 through February 10 each year. ^[7] Postponed taxes accrue 7% annual interest and come due when the property sells or transfers.

For low-income homeowners already behind on taxes, the Tax Collector can sometimes set up a payment plan before a property reaches tax sale. There is no formal application. Call the office directly and ask, because installment agreements do exist for hardship cases.

Veterans rated totally disabled (100%) and their surviving spouses may qualify for a larger exemption than the standard $100,000 offset. The California Department of Veterans Affairs has current program details. ^[13]

One last point. Many eligible homeowners never file the Homeowners' Exemption because nobody ever told them it existed. If you own and live in your primary residence in Contra Costa and have never filed, check with the Assessor. The savings are modest, but once you file, you get them every year without lifting a finger.

Where can I find my Contra Costa County property tax records and assessed value?

The Contra Costa County Assessor runs a public property search portal where you can pull any parcel's current assessed value, ownership history, and property characteristics. ^[4] You need either the APN or the property address to search.

The Tax Collector's portal shows current taxes owed, payment history, and delinquency status by APN. ^[5]

For sales history and neighborhood comps (the raw material of any appeal), the county recorder's office holds deed transfer records. Zillow, Redfin, and the MLS through a licensed agent all carry reasonably complete sales histories too. But for a formal appeal, confirm every comp sale through the county recorder or a title company, because online estimates sometimes botch square footage or sale dates, and a bad number sinks your case.

The Assessor's office at 2530 Arnold Drive, Suite 100, Martinez, CA 94553 is open for in-person questions. Staff can walk you through how your assessed value was built, which is worth doing before you decide whether to appeal. That conversation costs nothing. It either confirms your hunch that the assessment runs too high or turns up something you missed, like an exemption you never claimed.

If you decide to move ahead and want a structured DIY process, the TaxFightBack appeal kit gives you the comp worksheet, the adjustment method, and hearing prep materials to build a case the AAB actually responds to.

Frequently asked questions

When is the Contra Costa County property tax due date?

The first installment (covering July through December) is due November 1 and goes delinquent after December 10. The second installment (covering January through June) is due February 1 and goes delinquent after April 10. Missing either delinquency date triggers a 10% penalty on that installment. The Tax Collector's office at cccounty.us/taxcollector shows your current balance by parcel number.

How do I find my Contra Costa County property tax bill online?

Go to the Contra Costa County Tax Collector's website at cccounty.us/taxcollector and search by your Assessor's parcel number (APN) or property address. You can view the current bill, pay by eCheck with no fee, and see your full payment history. If you cannot find your APN, it appears on any previous tax bill or on the county Assessor's parcel search portal.

What is the deadline to appeal my property tax assessment in Contra Costa County?

The regular deadline to file an Application for Changed Assessment with the Assessment Appeals Board Clerk is November 30 of the current assessment year. For supplemental assessments triggered by a purchase or new construction, you have 60 days from the mailing date on the Notice of Supplemental Assessment. Missing these deadlines usually means waiting until the following year to appeal.

How much can my Contra Costa property tax assessment increase each year?

Under California's Proposition 13, the Assessor can raise your assessed value by no more than 2% a year, or the increase in the California CPI if that runs lower. This cap holds regardless of how much the property's market value has climbed. The only time assessed value can jump sharply is after a change of ownership or new construction, which triggers a reassessment to full market value.

What is the Homeowners' Exemption in Contra Costa County and how do I apply?

The Homeowners' Exemption cuts your assessed value by $7,000, saving roughly $70 a year at the base 1% rate. It applies to your principal residence. File once with the Contra Costa County Assessor's office by February 15 of the first year you qualify, and it renews automatically each year you stay in the home. You can file by mail or in person at 2530 Arnold Drive, Suite 100, Martinez.

Can I appeal my Contra Costa County property taxes without hiring a tax agent?

Yes. The Assessment Appeals Board process is built for self-represented owners. You file an application, gather comparable sales from the six months before and after the January 1 lien date, and present your evidence at a hearing. The filing fee is $30. Many residential cases settle by stipulation with the Assessor's office before a formal hearing, especially when the applicant brings clear, well-organized comp evidence.

What triggers a property tax reassessment in Contra Costa County?

Two events trigger a full reassessment to current market value: a change of ownership (sale, gift, most inheritances) and completion of new construction. The Assessor also runs annual reviews to catch unreported changes. Prop 19 parent-to-child transfers after February 16, 2021 generally trigger reassessment unless the child makes the home their primary residence within one year and the gain above the parent's base year value stays under $1 million.

What is a Mello-Roos tax in Contra Costa County and can I appeal it?

Mello-Roos Community Facilities Districts (CFDs) are special tax districts created under California's Mello-Roos Community Facilities Act to fund infrastructure in new developments. They appear as fixed dollar charges on your bill, separate from the ad valorem rate. You generally cannot appeal Mello-Roos charges through the Assessment Appeals Board because they are not based on assessed value. Your remedy is limited to the CFD's own administrative process or a challenge to the district's formation.

How do I get a property tax refund in Contra Costa County if I overpaid?

If you win an assessment appeal, the county refunds any overpayment plus interest at 3% a year under California Revenue and Taxation Code Section 5151. If the bill contains a math or billing error, contact the Auditor-Controller's office. Refund checks typically arrive within 90 days of a board decision or billing correction. For duplicate online payments, the Tax Collector's office processes refunds through the same payment channel.

How does Proposition 19 affect inherited property taxes in Contra Costa County?

Under Prop 19 (effective February 16, 2021), a child who inherits a parent's primary residence keeps the parent's assessed value only by moving in as their own principal residence within one year, and only if the property's market value does not exceed the parent's assessed value by more than $1 million. Inherited rental or vacation properties no longer carry the parent's low base year value; they are reassessed to full market value at transfer.

What happens if I don't pay my Contra Costa County property taxes?

Missing December 10 or April 10 triggers a 10% penalty on that installment. If a bill stays fully unpaid by June 30, the property enters tax default status and starts accruing redemption penalties at 1.5% per month on the unpaid amount. After five years in default, the property becomes eligible for a county tax sale by public auction. The Tax Collector can sometimes arrange payment plans for owners facing hardship.

Can seniors get a break on Contra Costa County property taxes?

Yes. California's Property Tax Postponement Program lets homeowners 62 or older with household income of $45,810 or less and at least 40% home equity defer current-year taxes at 7% annual interest until the property sells. Separately, disabled veterans and their surviving spouses may qualify for an exemption of $100,000 to $150,000 off assessed value. The standard $7,000 Homeowners' Exemption is also open to seniors who own their primary residence.

How do I contact the Contra Costa County Assessor's office?

The Assessor's office is at 2530 Arnold Drive, Suite 100, Martinez, CA 94553. The main phone number is (925) 313-7400. The Assessment Appeals Board Clerk, who handles appeal filings, is at 625 Court Street, Room 105, Martinez, and answers at (925) 655-2000. Both offices have online portals through cccounty.us for parcel lookup and appeal filing.

Sources

1. California State Board of Equalization, Proposition 13 Overview: Proposition 13 set the base property tax rate at 1% of assessed value and capped annual assessment increases at 2% or the CPI, whichever is lower
2. Contra Costa County Assessor's Office, official homepage: The Contra Costa County Assessor sets assessed values; the Auditor-Controller applies tax rates; the Tax Collector bills and collects
3. Contra Costa County Auditor-Controller, Tax Rate Book: Total property tax rates by taxing rate area for Contra Costa County, fiscal year 2023-24
4. Contra Costa County Assessor, Change of Ownership and New Construction reassessment guidance: Change of ownership and completion of new construction trigger reassessment to current market value under Proposition 13
5. California State Board of Equalization, Homeowners' and Disabled Veterans' Exemptions: Homeowners' Exemption reduces assessed value by $7,000; Disabled Veterans' Exemption ranges from $100,000 to $150,000 off assessed value with the higher amount for low-income households
6. California State Controller's Office, Property Tax Postponement Program: Property Tax Postponement Program eligibility: age 62 or older, household income $45,810 or less, at least 40% equity; applications accepted October 1 through February 10; interest rate 7% annually
7. California State Board of Equalization, Proposition 19 guidance: Proposition 19 (effective February 16, 2021) limits parent-child transfer exclusions to a primary residence used as the child's principal residence, up to $1 million above the parent's assessed value; allows owners 55 or older to transfer base year value up to three times statewide
8. Contra Costa County Clerk of the Board, Assessment Appeals: Assessment Appeals Board filing window opens July 2 and closes November 30; $30 filing fee for most residential properties; 60-day window for supplemental assessments; independent three-member board
9. California Revenue and Taxation Code, Section 5151 and Section 5097: Section 5151 provides 3% annual interest on property tax refunds; Section 5097 establishes four-year period to file refund claim after payment
10. California State Board of Equalization, Annual Report on California Property Taxes: California's average effective property tax rate as a share of market value is approximately 0.75-0.80% due to Proposition 13 assessment caps
11. U.S. Census Bureau, American Community Survey, Property Tax Data: Data underlying state-level property tax rate comparisons; California ranks in the lower third of states by effective property tax rate as a share of home value