Contra Costa County, California
Filing deadline: November 30 (earliest possible)
Regular assessment appeals must be filed between July 2 and November 30, per the State Board of Equalization's statewide filing-period listing. If the county Assessor does not mail assessment notices to all taxpayers by August 1, the filing period is extended to November 30 instead of September 15 (California Revenue & Taxation Code Section 1603).
What to file
appeal
Approximate effective tax rate
1.25% (published estimate, 2025)
County filing fee
$40
Look up your current assessed value on the county assessor's site →