What the Assessor Does

Since property taxes are calculated on the value of the property being taxed, "ad valorem" in Latin, it is vital to determine the value of the various kinds of property subject to taxation. It is also necessary to locate and describe the property being taxed so that the property can be reported and or inspected and then valued. In California's 58 counties the valuation function for property tax purposes rests with the elected County Assessor and the staff of the Assessor's office. 

The Assessor has always been independently elected in California by the voters of the County so that the position is not subject to pressure from the governing body of the county, cities or school and special districts to increase assessments in order to generate more revenue. The Assessor works for all the voters and property owners in the county and is charged with preparing fair and correct valuations based on objective market standards.

Locating Property

Locating real property, land, structures, and growing improvements is relatively straightforward from deeds, building permits and other property descriptions. The Assessor is charged with maintaining assessment maps which show each parcel of land and an assessment roll which describes the improvements on the property and the ownership of that property. An 1888 Assessment Ledger for Napa County still listed all the household effects including sewing machines, furniture and wagons as well as cattle and horses since all were taxable. This information was collected by Assessor office staff who visited the properties. In modern times household furnishings, most livestock, and business inventory have all been removed from the definition of taxable property.

Appraisal of Property

Until 1978 the entire county was subject to reappraisal on a four year cycle, with entire neighborhoods receiving increases in value based on recent sales in that area. Under Proposition 13 values are frozen at a 1975 base year value with adjustments for inflation limited to no more than 2% a year unless there has been a change in ownership or new construction. Thus the function of the assessor has gone from doing mass appraisal impacting many properties to an individual appraisal of properties that have changed hands or been added to. Ownership records are maintained from documents recorded with the County and maps are updated as parcels are subdivided or their boundaries adjusted. Building permits are reviewed for assessable new construction and appraisers make discoveries in the field.


When a property is reappraised for change of ownership, the appraiser still looks at comparable sales of like properties, or if the property produces income, she will do an income approach. Where the property is unique, the appraiser may use the owner's cost of construction (historic cost) or use costs based on industry-wide studies (replacement costs). Once a property has been valued, the owner is notified of the new value and given the opportunity to discuss the value with the appraiser. If there is still disagreement, the owner may apply for a changed assessment with the local board of equalization.

Personal Property

Personal property such as aircraft and boats are assessed each year based on "blue book" data gathered from market sales. Equipment used in a trade or business is also assessed every year using a formula based on original cost and age of the equipment.

More Information

If you have questions or comments about this column, please contact Napa County Assessor John Tuteur.