Supplemental Assessment Process

A Guide

On July 1, 1983, Senate Bill 813  changed the state Revenue and Taxation Code to create what are known as  Supplemental Assessments. This new law changed the manner in which changes in assessed value were billed by requiring that any increase or decrease in taxes due to a change in ownership or completed new construction became effective as of the first day of the month following the date of change in ownership or the date new construction was completed rather than on the next annual tax bill.
Supplemental assessments result in a one-time tax bill that is "in addition to" (that is, supplemental to) the annual property tax bill sent to property owners in October. Changes in ownership or completed new construction that trigger supplemental assessments are referred to as "supplemental events."

A supplemental event results in a reassessment. A reassessment may be an assessed value increase resulting in a supplemental bill, an assessed value decrease resulting in a supplemental refund or no change in value.

Depending on the date of the supplemental event, either one or two supplemental tax bills will be produced. Supplemental events that occur between January 1 and May 31 will generate two supplemental bills. Supplemental events that occur between June 1 and December 31 will generate one supplemental bill.

You may also receive more than one supplemental tax bill if more than one supplemental event has occurred in a fiscal year. If this occurs the bills are pro-rated between each owner for the period of time the property was owned.

  • Am I entitled to a Homeowners' Exemption on my supplemental tax bill?
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  • Are other exemptions available that might help lower my taxes?
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  • Can I file an appeal of a supplemental assessment?
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  • Can I make a partial payment if I can’t pay in full?
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  • How are supplemental taxes computed?
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  • If I pay property taxes through an impound account (i.e., with my mortgage payment), will my lender get my supplemental tax bill?
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  • What happens if I resell a property shortly after I purchase it?
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  • What happens when the Assessor reassesses my property?
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  • What is a supplemental tax bill?
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  • What qualifies as new construction or a change of ownership?
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  • When must supplemental tax bills be paid?
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  • When will I receive my supplemental bill?
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  • When will I receive my supplemental refund?
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  • Why did I receive a supplemental bill to repay a supplemental refund I previously received?
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  • Why would an owner receive more than one supplemental tax bill?
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  • Will I still receive an annual tax bill in October?
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