Assessor Does Not Do Assessments

While Assessor and assessment start with the same six letters, the two functions are totally unrelated and can be confusing to a property owner when reviewing the property tax bill that the County Tax Collector sends each October.

The primary purpose of that bill is to collect property taxes, which are based on the assessed value of the property. However, California law also permits local agencies such as municipalities, sanitation districts and resort improvement districts to attach to the bill certain assessments (also known as direct charges) unrelated to the assessed value of the property. With the passage of Proposition 218 in 1996, most of these assessments must be property related and usually require voter-approval. 

Assessments on tax bills in this county may be general, such as flood control maintenance or storm drain improvements, which are usually agency-wide, i.e. a municipality or the county. There are also more limited assessments such as water and sewer availability charges, bank stabilization and landscape maintenance, etc., which are usually only for a specific subdivision. In addition, the law permits the property tax bill to be used to collect charges for sewer and other municipal type services that are based on usage.


The primary difference between assessments, done by local agencies, and property taxes, based on values established by Assessor office staff, is how the two items are calculated. Assessments are established on a per parcel basis and under Proposition 13 cannot be related to the value of the parcel. Thus the flood maintenance assessment is based on the use of the parcel, the size of the structure if commercial or industrial and the amount of vineyard acreage. A single-story, 10,000-square-foot industrial building worth $500,000 pays a lesser amount than a single-story, 20,000-square-foot industrial building worth $400,000 because the calculation for commercial and industrial parcels is based on runoff generated by roof coverage, not on value.

Property Taxes

Property taxes (also known as ad valorem taxes from the Latin “by value”) are calculated on the value of taxable property including land, structural improvements and vines. Proposition 13 restricts the property tax rate to one% of the factored base year value. Thus property with a $100,000 factored base year value (the assessed or taxable value) will pay property taxes based on one% of $100,000 or $1,000. In addition Proposition 13 permits voter-approved bonds to be repaid using ad valorem taxes so most property owners in Napa County see a School Bond tax amount on their tax bills.

More Information

Questions regarding specific assessments should be directed to the agency responsible for that assessment (a list of phone numbers is shown on your tax bill.) Should you have any questions please contact Napa County Assessor John Tuteur at 707-253-4459 or email John.