The Assessor's Office first determines the new value of the property based on current market values. They then calculate the difference between the new value (set at the time of purchase or completion of new construction) and the old value (set on January 1 of the previous fiscal year). The result is the supplemental assessment value. Once the new assessed value of your property is determined, the assessor will send you a notification of the amount to be assessed.

For example:

  • New value at date of purchase or completion of new construction $120,000
  • Assessed value for current fiscal year $100,000
  • Supplemental assessment value will be $20,000

This reassessment usually results in an increase in property value, in which case your supplemental taxes will be calculated by the auditor-controller based on the change in value, and one or more supplemental tax bills will be created and mailed to you by the tax collector.

However, in some instances the reassessment results in a reduction in value, in which case a refund will be prepared by the auditor-controller and mailed to you. A reduction in value will not reduce the amount due on the annual secured tax bill.

The annual tax bill must be paid in the amount originally billed. If you think there's an error in the valuation of your property, please contact the assessor's office at 925-313-7400.