Compiling the Assessment Roll Part 1

The Schedule

The tax bills that Napa County property owners receive in mid-July (unsecured) and late October (secured) are based on values compiled by assessor office staff during the prior fiscal year. The deadline for the assessor to complete the local roll of assessed values is June 30. This roll is based on events that occurred between January 1 and December 31 of the year prior to that June deadline. Because assessor staff cannot begin working on the new roll until July 1 each year, there is already six months of work backlogged when the new cycle begins. The workload described below must be done in a careful and thorough manner to ensure that the assessment roll is both accurate and fair.

Changes to Assessment Roll

Changes to the annual assessment roll are caused by one or more of the following components:

  • Real property (land and structures) value changes caused by changes in ownership or new construction
  • Annual revaluation of personal property, including business equipment, boats and aircraft
  • Calculation of restricted values under the California Land Conservation (Williamson Act)
  • Granting exemptions to eligible homeowners, disabled veterans and submitting religious and charitable organizations exemptions to the State Board of Equalization for approval
  • Assessing possessory interests to holders of exclusive rights to non-taxable property, such as hangars at the Napa County Airport and employee housing at Napa State Hospital and the Veterans Home
  • Determining values of property which may have suffered declines in value because of real estate market conditions or natural disasters
  • Changes to assessor parcel configurations by parcel map or lot line adjustment;
  • Processing vine reports from vineyard owners
  • Applying the required Proposition 13 inflation factor, not to exceed 2%, to properties that have not otherwise had a value change


These tasks are performed by the joint effort of both members of the assessor staff, as well as our state-of-the-art computer system. Our transfer mapping staff tracks changes in ownership (approximately 4,000 per year) and in parcel configurations (approximately 200 per year) by reviewing deeds recorded with or maps filed with the Napa County Recorder and other sources. Once a change in ownership has been established or a new parcel has been created, the computer system generates a worksheet which goes to the appraisal staff to determine the change in value. 

To track new construction, support staff enter permit information received from the County and municipalities (approximately 2,000 per year) into the computer which again produces a worksheet for valuation. The appraisal staff reviews the permit information and makes property inspections as required to arrive at either a construction-in-progress or final value for the new construction. The new values set by the appraisers are reviewed by senior staff and then entered into the computer system by assessment support staff.
Personal property

Support staff also update our list of boats, aircraft and businesses in Napa County as of January 1 each year. Primary sources for these personal property owners are the California Department of Motor Vehicles and marinas for boats (approximately 2,150); Napa County and Angwin airports for aircraft (approximately 275); and business license lists and tenant rosters for businesses (approximately 6,400 per year). The owners are sent forms to report the condition and cost of their property. The forms are then processed by our Auditor-Appraisers and other staff using computerized valuation tables to arrive at values for the assessment roll. Read part two of compiling an assessment.

More Information

Should you have any questions please contact Napa County Assessor-Recorder-County Clerk John Tuteur at 707-253-4459 or email John.