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Understand a supplemental property-tax bill

Review BOE explanations of supplemental assessments, separate tax bills and impound-account limitations.

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Choose the county collector for your bill and payment method; the BOE and State Controller entries are shared state information, not local offices.
A due date and a delinquency date differ. Check the regular secured-roll calendar, the next-business-day rule, your bill type and the exact payment-channel cutoff.
The homeowners’ exemption reduces taxable assessed value. Proposition 19, supplemental bills and postponement each have separate conditions and filing rules.
Property-tax postponement is a loan-like deferment secured by a lien and must be repaid. Check the current programme year, funding and application conditions.

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California Board of Equalization — Property Tax Guidance

Shared California state property-tax information; actual claims, local bills, sale notices and individual eligibility require the responsible agency.

Supplemental assessments and separate tax billsOfficial instructions

Shared California state guidance. Follow the official programme conditions and the responsible county’s instructions; this entry does not establish individual eligibility or confirm an active local auction.

Supplemental assessment triggers

A qualifying change in ownership or completed new construction may create supplemental bills in addition to the annual bill.

Official information checked October 26, 2026 · Details & sources

Proration period

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.

Official information checked October 26, 2026 · Details & sources

Source checked October 26, 2026

California State Board of Equalization · Supplemental assessments (opens in a new tab)

Supplemental assessments and separate tax bills

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.

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