Buying in Solano County and just heard about a “supplemental” tax bill? You’re not alone. Many buyers are surprised when a second property tax bill arrives after closing. The good news is you can plan for it. In this guide, you’ll learn what a supplemental bill is, when it shows up, how the amount is calculated, and how to handle payments or appeals in Solano County. Let’s dive in.
Supplemental bill explained
A supplemental assessment happens when you buy a home or complete new construction. The Assessor revalues the property to current market value, then taxes the difference from the prior assessed value for the rest of the fiscal year. This is separate from your regular annual tax bill and follows statewide rules under Proposition 13. You can review the state overview in the California Board of Equalization’s guide on supplemental assessments.
When Solano issues bills
- Effective date: The new value takes effect the first day of the month after your closing month. If you close in March, the effective date is April 1. The Assessor will mail you a Notice of Supplemental Assessment.
- One or two bills: Close June through December and you typically get one bill for the remainder of that fiscal year. Close January through May and you can receive two bills, one for the remainder of the current year and one for the next full fiscal year. Details appear in the BOE’s supplemental assessment explainer.
- Annual bill still applies: Your supplemental bill is in addition to your annual secured tax bill. Each has its own due dates.
How the amount is calculated
The county follows a standard method:
- New market value minus the prior assessed value equals the net supplemental assessment.
- The net amount is multiplied by your parcel’s tax rate. California’s general levy is 1 percent, but your actual rate is often higher due to voter-approved items. Learn more about Prop 13’s framework from this overview of the 1 percent levy.
- That result is prorated based on months remaining in the fiscal year.
BOE proration factors by month
- January: 6/12 (0.50)
- February: 5/12 (0.42)
- March: 4/12 (0.33)
- April: 3/12 (0.25)
- May: 2/12 (0.17)
- June: 1/12 (0.08)
- July: 12/12 (1.00)
- August: 11/12 (0.92)
- September: 10/12 (0.83)
- October: 9/12 (0.75)
- November: 8/12 (0.67)
- December: 7/12 (0.58)
Quick example
Say the prior assessed value was 400,000 and your new value is 700,000. The net supplemental assessment is 300,000. If your combined tax rate is 1.10 percent, the annual tax on that difference is 3,300. If you closed in March, the proration is 4/12. Your supplemental tax would be about 1,099 for the rest of that fiscal year.
Who gets the bill and who pays
- The owner receives the supplemental bill directly. Lenders do not automatically receive or pay supplemental bills from escrow accounts. This is a common surprise for first-time buyers. See the state’s clarification in the BOE’s supplemental assessment guide.
- The name on the bill is responsible for paying by the due date shown. If you expect your lender to pay, confirm in writing with your lender and escrow company.
- You may receive more than one supplemental bill if there are multiple changes, such as a sale followed by improvements. Across all supplemental bills, you will not pay more than if the full value had been on the annual roll for the entire year.
Paying in Solano County
- Payment methods: Solano County accepts online, mail, and in-person payments. Start with the Tax Collector’s main page for the payment portal and current instructions.
- Due dates and penalties: Your bill shows exact due dates and penalties for late payment. The county posts annual mailings and schedules on its secured annual property tax bills notice. If you do not receive a bill, contact the Tax Collector promptly at (707) 784-7485 or [email protected], or visit 675 Texas Street, Suite 1900, Fairfield, CA 94533.
- Lender impounds: For escrowed accounts, confirm whether the lender will pay the supplemental bill. The county’s Tax Collector FAQ explains secured vs. supplemental bills and common lender issues.
Appeals and deadlines
If you disagree with the new base-year value on your Notice of Supplemental Assessment, act quickly. You have 60 days from the notice date or postmark to file an appeal. While an appeal is pending, you must still pay on time. Start with Solano County’s Assessment Appeals information for forms, fees, and filing windows. Statewide rules are summarized in the BOE’s supplemental assessment resource.
Buyer and seller checklist
At escrow
- Ask how supplemental taxes will be handled. Get lender confirmation in writing if they will pay from an impound account.
- Plan cash reserves for one or two supplemental bills, especially if closing January through May.
After closing
- Watch for the Notice of Supplemental Assessment. If it does not arrive, contact the Assessor and the Tax Collector.
- If your lender is not paying the supplemental bill, pay it by the due date to avoid penalties.
If you disagree with value
- Request an informal review with the Assessor. If not resolved, file a supplemental appeal within 60 days. Keep paying on time during the appeal.
Common pitfalls to avoid
- Assuming the lender will pay the supplemental bill without written confirmation.
- Missing a second bill after a January through May closing.
- Ignoring the Assessor’s notice and missing the 60-day appeal window.
- Underestimating the tax rate by using only 1 percent instead of your parcel’s full rate.
Buying or selling in Solano County is easier when you understand how property taxes work. If you want local guidance on budgeting for closing, planning for supplemental bills, or navigating appeals, the Loney & Worley Team is here to help you move forward with confidence.
FAQs
What is a supplemental property tax bill in Solano County?
- It is a separate bill that taxes the difference between your new assessed value after a sale or new construction and the prior assessed value for the remaining months of the fiscal year.
When will I receive my Solano supplemental bill after buying a home?
- After you close, the value is effective the first day of the next month, and the county mails a notice and then the bill, which can be one or two bills depending on your closing month.
Will my mortgage escrow pay my supplemental tax bill?
- Usually not automatically; supplemental bills are mailed to you, so confirm in writing with your lender if they will pay from your impound account.
How do I estimate my supplemental tax amount?
- Use this formula: (new value minus prior assessed value) times your parcel’s tax rate times the BOE proration factor for your effective month.
How do I appeal a Solano supplemental assessment and what is the deadline?
- File with the Solano County Assessment Appeals Board within 60 days of the notice date or postmark, and keep paying on time while your appeal is reviewed.
