Frequently Asked Question: What is a supplemental tax bill, and why did I receive it?

The County Treasurer/Tax Collector issues a supplemental tax bill when the assessed value of changes. The three most common events that trigger a supplemental tax bill are:

  • Change of Ownership
  • Death of Real Property Owner
  • Construction or Improvements

Supplemental tax bills are determined by taking the difference between your new assessed property value and the previous assessed property value.

Your supplemental tax bill(s) is due on the date(s) specified, and the time periods do not correlate with the regular tax year halves. Instead, they are only divided into two separate installments to give the taxpayer time to pay.

  • Los Angeles County Homeowners: For details on estimating a supplemental tax bill for a property being purchased in Los Angeles County click here:
  • For an explanation of the bill:
  • Orange County Homeowners:
  • Riverside County Homeowners:
  • San Diego County Homeowners:

Keep in mind that supplemental tax bills are a one-time obligation, unlike your annual property taxes that will recur.

What to expect in escrow
Any supplemental tax bills issued during escrow before or during escrow are paid by the seller. Buyers will see a debit on their statement reflecting the prorated amount they owe for the remainder of the tax year.

What to expect after close?
The County Assessor will update the tax roll and issue the supplemental tax bill about 8-12 months after a triggering event such as a purchase, construction, or death of the real property owner.

If you have any questions about prorated amounts or tax bills issued during escrow or on the preliminary title report, contact your escrow officer for more details.