Under the provisions of Proposition 13, a property must be reassessed at market value whenever there is a change in ownership or when new construction is completed; a new base year value is established and a supplemental assessment is created.

The new base year value must be the fair market value of the property on the date of the change in ownership. If a property has sold, and if the purchase price is the same as the market value, then the reported purchase price is enrolled as the new base year value. If the purchase price is significantly higher or lower than the fair market value of the property on the change of ownership date, the Assessor is required by law to enroll fair market value. That value is determined by conducting an appraisal.

A supplemental assessment represents the difference between the new base year value and the value on the Assessor’s records for the affected tax year(s). Changes that occur between January and May will create two supplemental assessments; changes occurring between June and December will create one supplemental assessment. The regular tax bill will be submitted one time only.

Supplemental assessments are effective the first day of the month following the month in which the change occurs. Supplemental assessments that occur because of an increase in assessed value results in a supplemental property tax bill(s). Supplemental assessments that occur because of a decrease in assessed value result in supplemental refunds being issued. The amount of the supplemental bill or refund is calculated by multiplying the tax rate by the supplemental assessment. Both supplemental bills and supplemental refunds are then pro-rated to cover only the time during the tax year that someone owns a property. Multiple activities during a tax year will result in multiple supplemental assessments; each bill or refund will be prorated to cover the assessee’s period of ownership.

The supplemental roll is separate from the regular roll. The regular roll is prepared once a year, as of January 1 (Lien date) and is delivered to the Auditor’s office each year on July 1. The supplemental roll is created throughout the year as changes are processed and it is delivered periodically throughout the year.

Supplemental bills or refunds are only mailed directly to the property owner.