Assessor Williamson Act Estimator

Parcel Number: (example: 123456789000 no dashes)
Estimated Additional Tax Due to Change in Williamson Act Contract

This page provides an estimate to illustrate the affect of the Williamson Act additional taxation based on the Williamson Act value vs. the factored base year value (also called the Proposition 13 value). This is not a basis for a tax bill and should not be used to estimate future tax bills. The tax bills on all properties in California are generated based on values as of January 1. Williamson Act values can move up or down each year as long as the value is below the Proposition 13 value which was established at the time the property was acquired. Williamson Act Valuation Notes

Williamson Act values are calculated using land rents and other market data for different types of trees and vines. From this information an income is attributed to both land and trees and vines and this income along with other factors are used to determine the Williamson Act values.

A value for a home site, if present, and any buildings or other types of structures are determined at the time of a sale or transfer and valued under the rules for Proposition 13.

These values are combined with the Williamson Act values and the total becomes the potential assessed value for properties under a Williamson Act contract. It only becomes the assessed value when the entirety of the property is valued under the rules for Proposition 13 and the lower of the two values are determined.

For Example:

Williamson Act Value Proposition 13 Value
Total $223,000 $325,000

In this example, since the Williamson Act value is the lower of the two values it would be used for assessment purposes. The $102,000 difference in value is the savings you would see in your assessed value because of the Williamson Act. Using a 1% general property tax rate your savings in property taxes would be $1,020.