Real Property


The value enrolled at the time the property is acquired (or the 1975 value if acquired before 1975) is the property’s base year value. This value is increased annually by a factor that is based on the California Consumer Price Index or 2%, whichever is less. This value is referred to as the Proposition 13 value. 

Building permits, which are received by the Assessor from all cities and the County, are the primary method of discovering new construction. As of the date of completion of the new construction, the “added value” will be determined and added to the property’s existing assessed value. This typically results in a supplemental assessment.

Major renovation or rehabilitation of a structure, which makes it substantially the equivalent of new construction, or which changes the use of the property, may be considered as new construction. Normal repairs, replacement, or maintenance such as replacing a roof, replacing kitchen appliances, or replacing plumbing fixtures are typically excluded from reassessment. As of the date of completion of the major renovation, rehabilitation, or change in use, the “added value” will be determined and added to the property’s existing assessed value. This typically results in a supplemental assessment.

If the new construction is incomplete on the lien date (January 1), a value reflecting what exists will be added for the upcoming tax year. This value is referred to as the “Construction In Progress” value.

Under the provisions of Proposition 13, property must be reassessed at market value whenever there is a change in ownership or 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. If a property has sold, and 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 date, the Assessor is required by law to enroll the 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 or years. 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 only be issued once and will remain unchanged.

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 result in supplemental property tax bills. 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 times 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 an assessee’s period of ownership.

The supplemental roll is completely separate from the regular roll. The regular roll is prepared once a year. It is effective January 1 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 always mailed directly to the property owner.

New construction built for resale may be excluded from supplemental assessment under certain conditions. The builder must file the necessary form with the Office of the Assessor before or within 30 days of the start of construction. Download the Claim for New Construction Exclusion from Supplemental Assessment form. For more information, call the Office of the Assessor at (209) 468-2658.

State law provides that when the current market value is less than the Proposition 13 value (value at the time of acquisition plus annual inflation factor up to 2%), the market value is to be enrolled for that tax year. These properties are then reviewed annually, and the current market value continues to be enrolled until that value is greater than the Proposition 13 value. During this time, under Proposition 8, the annual property value may increase more than 2% per year until the Proposition 13 value is restored.

Agricultural landowners who sign a contract with the County placing their land in the Williamson Act will have their agricultural land and living improvements valued according to a special form of income capitalization. The value is generally lower than the Proposition 13 value. These values are recalculated annually. Home sites, non-living improvements, and outbuildings are valued on the same basis as other property under Proposition 13.

Ownership, Title, and Registration of Manufactured Homes are administered by the State Department of Housing & Community Development (HCD).

Manufactured homes sold on or after July 1, 1980, are subject to property taxation.

For many manufactured homes sold before this date, taxes are waived by the County unless they have elected for Voluntary Local Property Taxation. Rather, they are registered annually and licensed with the State Department of Housing & Community Development (HCD).

All manufactured homes placed upon permanent foundations are subject to local property taxation, regardless of the date first sold.

Owners of manufactured homes subject to property taxation are eligible for the same exemptions and exclusions as real property owners.

If you disagree with your assessed value, first contact the Office of the Assessor to request a review of the value. Informal Review Applications must be filed by September 15th.

If you are unsatisfied with the outcome, you may file an appeal with the Assessment Appeals Board. Appeals for the regular roll must be filed between July 2 through November 30. Appeals to the supplemental roll must be filed within 60 days of the supplemental notice date.

An Assessment Appeal application, filing dates and information about the Assessment Appeals process are available online with the Clerk of the Board. You can reach the Clerk of the Board at (209) 468-2350 for more information.