Property Tax Appeals in Contra Costa County, California
Contra Costa County's Clerk of the Board states that Regular Assessment Appeals must be filed between July 2 and November 30 of each calendar year. The county's posted filing instructions direct an applicant to mail the completed Assessment Appeal Application and a $40 check to the Assessment Appeals Board in Martinez; the page does not describe an online filing option. Assessment Appeals is staffed from within the Clerk of the Board by the Assessment Appeals Secretary and is separate from the Assessor's Office. FairPath can organize an owner-managed comparison table, condition exhibits, official links, and a filing checklist. It does not file the application, select the owner's opinion of value, pay the fee, negotiate with the Assessor, or appear at the hearing.
Assessment context: Begin with the Assessor's parcel record and identify whether the dispute concerns the January 1, 2026 lien-date value on the regular roll, a supplemental assessment tied to a change of ownership or new construction, or an escape assessment. Contra Costa County combines dense Bay Area cities such as Richmond, Concord, and Walnut Creek in the county's western and central areas with more suburban and semi-rural communities toward Brentwood and Oakley in the east county, plus hillside and view parcels throughout. A property a few miles away is not automatically comparable. Neighborhood, lot topography, view, age, and condition should be confirmed against the Assessor's record before relying on them.
Filing process: Download the Assessment Appeal Application from the Clerk of the Board's Assessment Appeals page and review the accompanying Application Fee Information and Rules on Assessment Appeals documents before signing. Complete the form, identify the parcel and assessment year, state the applicant's opinion of value, and mail it together with a $40 check to Assessment Appeals Board, 1025 Escobar Street, 1st Floor, Martinez, CA 94553. Keep a copy of the signed application and proof of mailing. Assessment Appeals Board meeting agendas are posted on the county's Agenda Calendar, and property taxes remain due while the appeal is pending.
Evidence to review: California law lets either the applicant or the Assessor's Office request an exchange of comparable-sales and appraisal information before a Contra Costa Assessment Appeals Board hearing under Revenue and Taxation Code Section 1606. Build a comparable-sales table showing sale date, price, parcel, neighborhood, lot size, living area, age, and condition, and prioritize sales close to the January 1, 2026 lien date; California generally excludes comparable sales occurring more than 90 days after that date. Because Contra Costa spans flat valley subdivisions and hillside view lots, document topography, access, and view differences alongside dated photographs or inspection reports that support a condition-based adjustment.
Current deadline guidance: 2026 regular assessment appeals: July 2 through November 30, 2026. Contra Costa County's Clerk of the Board states that Regular Assessment Appeals must be filed between July 2 and November 30 of each calendar year, consistent with the California State Board of Equalization's certified county filing-period table for 2026. Supplemental or escape assessments instead must be filed within 60 days of the notice from the Assessor.
Contra Costa County uses the extended November 30 regular filing deadline rather than the earlier September 15 deadline used by some other California counties.
The county's posted filing instructions direct applicants to mail the application and a $40 check to the Assessment Appeals Board in Martinez rather than file online.
Assessment Appeals is staffed from within the Clerk of the Board by a dedicated Assessment Appeals Secretary, separate from the Assessor's Office.
Assessment Appeals Board hearings and agendas are posted on the county's public Agenda Calendar in advance of each meeting.
Official filing authority: Contra Costa County Clerk of the Board, Assessment Appeals. https://www.contracosta.ca.gov/2924/Assessment-Appeals
Source: Contra Costa County Clerk of the Board, Assessment Appeals, https://www.contracosta.ca.gov/2924/Assessment-Appeals. Reviewed 2026-09-22.
Source: Contra Costa County, Assessor, https://www.contracosta.ca.gov/191/Assessor. Reviewed 2026-09-22.
Source: California State Board of Equalization, Letter to Assessors 2026/023: 2026 Assessment Appeal Filing Periods, https://boe.ca.gov/proptaxes/pdf/lta26023.pdf. Reviewed 2026-09-22.
Visit FairPath with JavaScript enabled for the full experience.