Sonoma County clerk-recorder-assessor briefs Cloverdale council on $127 billion assessment roll, explains Prop. 13 and Prop. 19 effects

Diva Marie Proto, Sonoma County Clerk-Recorder-Assessor, told the Cloverdale City Council on Aug. 13 that the county’s 2025 assessment roll totaled just over $127 billion and increased 5.44% from the prior year, with most growth in secured property values.

Why it matters: The assessed value determines the taxable base that the auditor-controller and tax collector use to calculate property tax bills; changes in assessed value affect future tax revenues for local agencies.

Proto said all values on the roll are based on market conditions as of Jan. 1, 2025, and the roll is transmitted to the auditor-controller on June 30. She reminded the council that the tax bills residents receive next spring reflect market value as of Jan. 1, 2025. She added that role corrections and supplemental assessments for changes in ownership or new construction can produce assessments and tax bills at other times in the year.

Proto explained how Proposition 13 limits annual assessment growth to a maximum of 2% or the CPI for properties that do not change ownership, and that transfers or new construction can trigger reassessment. She said the county uses a combination of cost, sales comparables and other methods to value features such as accessory dwelling units (ADUs).

On Proposition 19, Proto said the voter-approved law allows eligible homeowners to transfer their tax base within the state up to three times, which can move a low tax base from one county to another. She also described new, narrower rules for intergenerational transfers: to preserve a parent’s tax base when transferring to a child, the property must be the parent’s principal residence and must become the child’s principal residence; otherwise, the property will generally be reassessed at market value.

Proto said the county has experienced a backlog of assessments dating to the 2017 fires and is working to reduce it, and that Cloverdale’s local assessment growth for the year was about 3.59%, lower than some neighboring jurisdictions.

When asked how ADUs are treated, Proto said the assessor values the ADU at market value as of the date of completion or transfer and uses comparables and construction cost factors rather than assuming the owner’s construction cost equals market value.

No council votes were taken on the presentation. Proto provided contact information for follow-up questions.