Supplemental Assessments
The supplemental roll provides a mechanism for placing property subject to Proposition 13 reappraisals due to change in ownership or completed new construction into immediate effect.
Changes in ownership or completed new construction are referred to as 'supplemental events' and result in supplemental tax bills that are in addition to the annual property tax bill.
The increase (or decrease) in assessed value resulting from the reappraisal is reflected in a prorated assessment (a supplemental bill) that covers the period from the first day of the month following the supplemental event to the end of the fiscal year. A fiscal year runs from July 1 through June 30.
Supplemental Assessment
Revenue and Taxation Code sections 75–75.72 detail the laws governing the supplemental assessment process.
When a supplemental event occurs, the county assessor determines the current market value of the property that changed ownership or that was newly constructed.
The assessor then subtracts the property's prior assessed value from its newly assessed value, and the difference between the two is the net supplemental value that will be assessed and enrolled as a supplemental assessment.
The supplemental assessment may be either a positive amount or, in the case of a reassessment that is less than the prior assessed value, a negative amount.
Supplemental bills (or refunds) are calculated based on the number of months remaining in the current fiscal year after the month in which the supplemental event occurs.
A fiscal year runs from July 1 through June 30.
If the net supplemental assessment is positive, the increase in taxes will be calculated by the County Auditor-Controller based on the change in value.
One, or possibly two, supplemental tax bill(s) will be generated and mailed by the county tax collector.
If a supplemental event occurs between June 1 and December 31, only one supplemental tax bill or refund check is issued. This bill, or refund, accounts for the property's change in value for the period between the first day of the month following the event date and the end of the current fiscal year (i.e., the following June 30).
If, however, a supplemental event occurs between January 1 and May 31, two supplemental tax bills or refunds are issued. The second bill or refund accounts for the property's change in value for the entire 12 months of the coming fiscal year, beginning on the following July 1.
The supplemental tax bill is sent in addition to the regular annual tax bill and both must be paid as specified on the bill.
There are two ways to appeal a supplemental assessment.
-
To request an assessment review, contact the Marin County Assessor at 415-473-7215 to request an Informal Assessment Review.
-
Formally appeal through the Board of Supervisors. Here are a few criteria:
-
File appeal within 60 days of the mailing date on the Supplemental Tax Bill
-
Pay tax bills by the deadlines to avoid penalties.
-
Contact County Assessor: 415-473-7215
- Questions about the Value of Property, Exemptions, or Ownership.
Contact County Auditor-Controller: 415-473-6168
-
Questions about revised bills and calculations.