How do Supplemental Property Tax Bills work?

Property tax bills can be very confusing after you purchase a home. Not only do you receive the regular tax bills, but you also receive “supplemental” tax bills. In addition, for some odd reason property taxes aren't due in uniform increments**. So how does this all work?

(original article updated to reflect most recent tax year)
2024-2025 Tax Bills are sent out in late September of 2024 for both installments (the 1st installment is due November 1, 2024…late December 10, 2024. The 2nd installment is due February 1, 2025 and late April 10, 2025).  

The tax bills will show amounts due for the previous owner (based on his/her value basis). Then you will be sent a supplemental bill(s) with the difference for your new value basis (based on your purchase price)…this will be applied by the county according to the date you took possession. These supplemental tax bills essentially adjust for the property value change from the previous owner’s basis to your new basis.
 
For those with impound accounts, supplemental tax bills are not automatically sent to loan servicers. Therefore, you may have to notify your loan servicer and send a copy of the bills over in order to get them paid by your servicer (assuming your impound account is sufficiently funded). Otherwise, the supplemental bills must be paid by you. Supplemental bills generally only occur in the first year and cease once the regular property tax bills reflect your accurate value basis for property taxes.

As such, the 2025-2026 Tax Bills will be sent out in late September of 2025 with the correct amounts…no more supplemental bills at that point to update the value basis. The 1st installment for this bill is due November 1, 2025 (late December 10, 2025). The 2nd installment is due February 1, 2026 (late April 10, 2026).

We hope this helps clear up how the county’s supplemental taxes work.

Let us know if you have any questions we can help answer.

**This article is based on the property tax structure for Southern California. Details may vary based on your county’s particular policy.

Updated 1/22/2025