Supplemental tax bill San Diego
Supplemental tax bill amount, mailing and timing
- The County bills the rise in assessed value at 1 percent plus bonds, from the first of the month after the sale or new construction to June 30.
- The Treasurer-Tax Collector mails the supplemental bill to the owner only, and the owner asks the lender whether it will pay the bill from the impound account.
- The County sends two bills for a purchase between January and May: one for the rest of the fiscal year and one for all of the next.
The Treasurer-Tax Collector bills a change in assessed value separately from the annual bill, generally six to twelve months after a sale or new construction.
What is a supplemental tax bill
The County collects the tax on a change in assessed value for the rest of the fiscal year through a supplemental tax bill. The Assessor issues a supplemental assessment after a change of ownership or completed new construction, unless the Assessor approves an exclusion, such as the parent-child exclusion.
How the supplemental property tax bill is prorated
- The County Auditor and Controller prorates the tax from the first day of the month after the event to June 30, one-twelfth for each month left.
- Supplemental tax: value change × tax rate (1 percent plus voter-approved bonds) × proration factor.
Supplemental tax on a $900,000 Clairemont purchase in September
A Clairemont buyer closes on September 15, 2026, and the Assessor raises the home's value from $500,000 to $900,000:
- Value change: $900,000 − $500,000 = $400,000
- Full-year tax at the County's 2025-26 average rate: $400,000 × 1.16729 percent = $4,669.16
- Supplemental tax bill, 9 months from October 1: $4,669.16 × 0.75 = $3,501.87 (2026-27)
- For a March 15 closing: $4,669.16 × 0.25 = $1,167.29, plus a second bill of $4,669.16 for 2027-28
Supplemental tax bills, lenders, refunds and appeals
- The Treasurer-Tax Collector cancels no penalty caused by a misunderstanding between the owner and the lender.
- For a lower value, the Treasurer-Tax Collector mails a negative supplemental bill and refund check, which the owner can apply to other open bills on the parcel.
- The owner pays the annual bill in full after a negative supplemental bill.
- An owner who disputes the new value appeals to the Assessment Appeals Board within 60 days of the bill's mailing date and keeps paying meanwhile.
Supplemental tax bill San Diego due dates and penalties
Delinquent dates by mailing month (Revenue and Taxation Code section 75.52):
| Bill mailed | First installment delinquent | Second installment delinquent |
|---|---|---|
| July to October | December 10 | April 10 |
| November to June | Last day of the month after mailing | Last day of the fourth month after the first delinquent date |
- The Treasurer-Tax Collector adds a 10 percent penalty to a late installment, plus $10 on a late second installment.
- With either installment unpaid at June 30, the Treasurer-Tax Collector puts the property in tax default and adds 1.5 percent a month and a $33 redemption fee.
San Diego County transfer tax at closing
- The San Diego County Recorder collects a documentary transfer tax of $0.55 per $500 of value, or $1.10 per $1,000, at recording, for the County and its cities.
- The Recorder taxes the value or price minus any existing liens or encumbrances, on transfers over $100.
- Transfer tax on a $900,000 sale with no lien carried over: $900,000 ÷ $500 × $0.55 = $990
When to hire a CPA for a supplemental tax bill
Bring in a CPA when the owner rents out a new unit or home: the owner deducts the rented share of the supplemental tax from rental income. Before hiring, check how to choose a CPA.