Los Angeles County Supplemental Property Tax Bill Explained
Learn what a Los Angeles County supplemental property tax bill is, why new homeowners receive one in addition to the annual bill, how the charge is calculated and prorated, and practical steps to handle it.
What a supplemental property tax bill is (and why you might get one)
A supplemental property tax bill is an additional tax bill you may receive when your property is reappraised because of a change in ownership or completed new construction. [1] It’s issued separately from your Annual Secured Property Tax Bill and does not replace that annual bill. [2] In Los Angeles County the supplemental billing process can produce two bills: the first covers the remainder of the fiscal year in which the triggering event occurred, and a second bill can arrive for the subsequent fiscal year. [3]
Why you might get one
- If ownership of the property changes, the county can reappraise the property and issue a supplemental bill for the difference between the prior assessed value and the new assessed value. [1]
- If new construction is completed, the county can reappraise for the added value from that construction and issue a supplemental bill. [1]
How it relates to your regular tax bill
- The supplemental bill is in addition to — and does not replace — the Annual Secured Property Tax Bill you already receive. [2]
- In practice, that means you could receive both your regular annual tax bill and one or two supplemental bills during a fiscal year. [3]
If you receive a supplemental bill, review the assessed-value change listed on it and contact the county assessor or treasurer if you have questions about the reappraisal or the timing of the supplemental billing. [1]
How supplemental taxes are calculated and what you’ll be charged
When a change in ownership or new construction triggers a reassessment, the county issues a supplemental tax bill that covers the increase in assessed value above the property’s previous assessment. [4] For more detail, see . Contra Costa County Property Tax Due Dates and How to Pay.
The supplemental bill is based on the difference between the property’s previous assessed value and its new assessed value, which is generally the purchase price. [4]
Because the change can occur at any point during the fiscal year, the first supplemental bill covers the remainder of the fiscal year in which the event occurred. [3]
If the reassessment takes effect before the end of a fiscal year, you may also receive a second supplemental bill that covers the next fiscal year. [3]
Supplemental taxes are prorated from the date of the qualifying event (for example, the closing date) through the end of the fiscal year on June 30, so the first bill reflects only that partial-year period. [1]
In practice this means you could get one bill for the remainder of the current fiscal year and a separate bill for the following fiscal year if the reassessment spans both periods. [3]
If you receive supplemental bills after a purchase or completion of construction, review the assessed values shown on the bill and compare them to your purchase price or new construction valuation to confirm the difference that produced the supplemental assessment. [4]
If anything looks incorrect, contact the assessor’s office for clarification and follow the appeal instructions they provide. [1]
When the supplemental bill arrives and what to expect
When the supplemental bill arrives and what to expect
Quick overview
- Expect a supplemental bill after your property is reappraised. [3]
- The supplemental bill is mailed in addition to the Annual Secured Property Tax Bill — it does not replace that annual bill. [2]
- Timing can vary; new owners should watch their mail and official county tax websites for notices. [2]
Steps
- Watch for the first supplemental bill: the county issues a first Supplemental Bill that covers the remainder of the fiscal year in which the triggering event occurred. [3]
- Watch for a second supplemental bill: the county may also issue a second Supplemental Bill for the subsequent fiscal year. [3]
- Remember this is in addition to your regular annual tax bill: the supplemental bill will arrive separately and does not replace the Annual Secured Property Tax Bill. [2]
- Stay alert for timing and delivery: because the county’s mailing schedule depends on when the property is reappraised, timing can vary, so check your mail and the official county tax pages for notices. [2]
- If you’re a new owner, monitor both the mailed notices and the county’s websites to make sure you don’t miss either supplemental or annual bills. [2]
If you need more detail about what appears on the supplemental bill or how the amount is calculated, check the county’s supplemental bill page or contact the Treasurer and Tax Collector’s office for guidance. [3]
Practical steps to handle a supplemental tax bill
Practical steps to handle a supplemental tax bill
- Verify the assessed values used on the supplemental bill: confirm the previous assessed value and the new assessed value that the county used to calculate the supplemental tax, and check the proration dates shown on the bill. [4] [3]
- Budget for the supplemental bill in addition to your regular annual tax bill, because the Supplemental Secured Property Tax Bill is in addition to the Annual Secured Property Tax Bill and does not replace it. [2]
- Note that supplemental billing can occur twice: the first Supplemental Bill covers the remainder of the fiscal year in which the change occurred, and a second Supplemental Bill can cover the subsequent fiscal year, so plan cash flow accordingly. [3]
- Contact the Los Angeles County Assessor or the Treasurer & Tax Collector if anything on the bill is unclear, and ask whether your escrow or impound account will cover supplemental bills so you aren’t surprised by an unexpected payment. [2]
- If you believe the new assessed value is incorrect, follow the county’s assessment appeal procedures to dispute the value rather than ignoring the bill. [4]
- Keep documentation from your purchase and any communications with county offices; accurate records will help if you need to appeal or reconcile proration dates and assessed values. [4]
Claims:
Common questions about LA County supplemental tax bills
Does the supplemental bill replace my annual property tax bill?
No — the Supplemental Secured Property Tax Bill is in addition to the Annual Secured Property Tax Bill, not a replacement. [2]
How many supplemental bills will I get?
You will often receive one supplemental bill for the remainder of the fiscal year in which the event occurred and a second supplemental bill for the following fiscal year, depending on timing. [3]
On what basis is the supplemental amount calculated?
Supplemental bills are based on the difference between the old assessed value and your new assessed value, which is generally your purchase price. [4]
Who issues these supplemental bills?
Supplemental Secured Property Tax Bills are issued through Los Angeles County property tax offices responsible for supplemental assessments and billing. [3]
What should I do if I have questions about a supplemental bill?
Contact the Los Angeles County Treasurer and Tax Collector or the Assessor’s office for details specific to your property and bill. [2]
Claims:
- text: "The Supplemental Secured Property Tax Bill is in addition to the Annual Secured Property Tax Bill; it does not replace the Annual Secured Property Tax Bill."
material: true
evidenceRef: E2
quote: "The Supplemental Secured Property Tax Bill is in addition to the Annual Secured Property Tax Bill; it does not replace the Annual Secured Property Tax Bill." - text: "The first Supplemental Bill is for the remainder of the fiscal year in which the event occurred. The second Supplemental Bill is for the subsequent fiscal year."
material: true
evidenceRef: E1
quote: "The first Supplemental Bill is for the remainder of the fiscal year in which the event occurred. The second Supplemental Bill is for the subsequent fiscal year." - text: "Supplemental bills are based on the difference between the old assessed value and your new assessed value, which is generally your purchase price."
material: true
evidenceRef: E4
quote: "Supplemental bills are based on the difference between the old assessed value and your new assessed value, which is generally your purchase price." - text: "Supplemental Secured Property Tax Bills are in addition to the Annual Secured Property Tax Bill."
material: false
evidenceRef: E1
quote: "The first Supplemental Bill is for the remainder of the fiscal year in which the event occurred. The second Supplemental Bill is for the subsequent fiscal year." - text: "Contact the Los Angeles County Treasurer and Tax Collector or the Assessor’s office for details specific to your property and bill."
material: false
evidenceRef: E2
quote: "The Supplemental Secured Property Tax Bill is in addition to the Annual Secured Property Tax Bill; it does not replace the Annual Secured Property Tax Bill."
Bottom line: be prepared and check the details
Bottom line: be prepared and check the details
Supplemental property tax bills are a normal part of revaluation when you buy a property or complete new construction, and they are in addition to your regular annual tax bill, not a replacement for it [2].
You can receive two supplemental bills related to a qualifying event: the first covers the remainder of the fiscal year in which the event occurred, and the second covers the subsequent fiscal year [3].
Supplemental bills are calculated on the difference between the prior assessed value and your new assessed value, which is generally your purchase price, so the supplemental amount reflects that increase in assessed value [4].
Because supplemental bills are additional to the annual bill, it’s wise to confirm the assessed values shown, plan for the extra cost when budgeting after a purchase or new construction, and contact Los Angeles County offices promptly if anything looks incorrect or you need clarification [2].
If something appears wrong—such as an incorrect assessed value—reach out to the Los Angeles County Assessor or Treasurer and Tax Collector to verify records and discuss next steps [3][2].
Keeping a close eye on both your annual and any supplemental notices will help you avoid surprises and ensure you address questions or appeals quickly.
Claims:
- Supplemental property tax bills are a normal part of revaluation when you buy a property or complete new construction, and they are in addition to your regular annual tax bill, not a replacement for it. (material: true) [2]
- You can receive two supplemental bills: one for the remainder of the fiscal year in which the event occurred and a second for the subsequent fiscal year. (material: true) [3]
- Supplemental bills are calculated on the difference between the prior assessed value and your new assessed value, which is generally your purchase price. (material: true) [4]