Yes. You may take the matter up with the Assessor to see if that office will change the valuation. Additionally, the Board of Supervisors has established an Assessment Appeals Board for the purpose of resolving valuation problems in connection with supplemental tax bills.
Applications for appeal must be filed within sixty days of the mailing date shown on the assessment notice. If you choose to appeal your assessment, you should still pay your tax installments in full by the appropriate deadlines; otherwise, you may incur penalties while the case is in appeals. If your appeal is granted, a refund will be issued to you.
Further information about the appeals process can be obtained by calling (925) 335-1901 or writing to: Clerk of the Assessment Appeals Board, 1st Floor, Suite 150, 1025 Escobar Street, Martinez, CA 94553