Supplemental Assessments

The supplemental roll provides a mechanism for placing property subject to Proposition 13 reappraisals due to change in ownership or completed new construction into immediate effect.

How it works

When a supplemental event occurs, the Assessor determines the current market value of the property that changed ownership or that was newly constructed. The Assessor then subtracts the property's prior assessed value from its newly assessed value, and the difference between the two is the net supplemental value that will be assessed and enrolled as a supplemental assessment.

Once the new assessed value of your property has been determined, the Assessor will send a Notice of Supplemental Assessment to the assessee.

After the required period, the Assessor will enroll the supplemental assessment. If the net supplemental assessment is positive, the increase in taxes will be calculated by the Auditor-Controller based on the change in value. One, or possibly two, supplemental tax bill(s) will be generated and mailed by the Tax Collector. If the net supplemental assessment is negative (a reduction in value), the Auditor-Controller will issue one, or possibly two, supplemental refund(s).

Examples

Here are some examples to help you understand how a supplemental event at different times of the year ....

1. Supplemental event occurs on March 3, 2022, Effective April 1, 2022

You purchased a home, which has a fair market value of $850,000 on March 3, 2022.
The previous assessed value was $400,000.

2. Supplemental event occurs in October 15, 2022, Effective November 1, 2022

You completed an addition on your home on October 15, 2022. The fair market value of the new construction is $35,000.

3. Supplemental event occurs in November 8, 2022, Effective December 1, 2022

You purchased a home, which has a fair market value of $750,000 on November 8, 2022. The previous assessed value was $790,000

Frequently Asked Questions