What is a supplemental property tax bill? In California, it bills an adjustment resulting from a property's reassessment after a qualifying ownership change or completed new construction. It is separate from the regular annual property tax bill. The assessment change can also produce a refund rather than an additional charge. California Board of Equalization: Supplemental assessment.
This is educational information, not tax or legal advice. The county's records, your actual bills and applicable law determine your obligations.
What is the difference between an assessment notice and a tax bill?
An assessment concerns the value used for property taxation. A tax bill requests payment. Similar-looking documents can serve different purposes:
| Document | What it communicates |
|---|---|
| Notice of Supplemental Assessment | The assessor's change in assessed value associated with the reassessment event. |
| Supplemental property tax bill | The additional tax billed for the applicable period because of that assessment change. |
| Regular annual property tax bill | The property's annual tax charges; a supplemental bill does not replace it. |
The assessor establishes assessed values; the tax collector handles billing and collection. A notice showing a value change is not itself proof that the resulting tax has been paid. California Board of Equalization, Alameda County Treasurer-Tax Collector: Tax FAQs.
Why might a new owner receive more than one supplemental bill?
The number of bills can depend on when the reassessment event occurs relative to the tax year. California's property-tax fiscal year runs from July through June, and an event can affect more than one billing period. Multiple ownership changes or construction events can also produce multiple adjustments. Two bills are not necessarily duplicates. California Board of Equalization.
The dates and assessment event identified on the actual documents are more useful than assuming every buyer receives the same number of bills.
Will a mortgage impound account automatically pay it?
Not necessarily. An impound account is money held by a mortgage servicer for expenses such as property taxes and insurance. Supplemental tax bills are generally sent to the owner and are not automatically covered by that payment arrangement. Confirm the handling of the actual bill with your servicer; having taxes included in the monthly mortgage payment is not proof that a supplemental bill has been paid. Orange County Treasurer-Tax Collector: Supplemental property tax FAQs.
Does a supplemental bill follow the annual bill's payment dates?
Do not assume so. Supplemental-bill delinquency dates can depend on when the bill was mailed. San Francisco's Tax Collector publishes a separate supplemental schedule. Use the dates on the bill and the issuing county's guidance, rather than a general annual-tax calendar. San Francisco Treasurer & Tax Collector: Secured and supplemental taxes.
What is an escape assessment?
An escape assessment addresses assessed value that was not properly included for an earlier period. The term can appear when reassessment is processed after a delay. It is distinct from a supplemental assessment; the label alone does not explain the full history of an individual bill. San Francisco Treasurer & Tax Collector.
Where do East Bay and San Francisco owners find official information?
For Oakland, Berkeley, Alameda and Albany properties, the Alameda County Treasurer-Tax Collector provides billing explanations and routes assessment questions to the assessor. For San Francisco property, the Treasurer & Tax Collector explains secured, supplemental and escape bills. Properties in other East Bay counties have their own county offices.
Professional boundary
This article does not estimate your tax bill, determine an exemption or advise on an appeal. The assessor and tax collector address assessment and billing records; a qualified tax or legal professional can address your circumstances. Westin can help explain the real estate terminology and identify the appropriate resource.