Property tax basis is the dollar value the assessor uses to calculate what you owe
Property tax basis is the assessed value of your property — the number your local assessor decides your home or land is worth. Your county or municipality multiplies this basis by the local tax rate (usually expressed as a percentage or per $1,000 of value) to arrive at your annual property tax bill. If your basis is $300,000 and your tax rate is 1%, you owe $3,000 that year.
The basis is not the same as what you paid for the property, what a real estate agent says it's worth, or what you could sell it for today. It is a separate number set by a government assessor, and it changes over time based on local assessment practices and state law.
Understanding your basis matters because it is the foundation of your tax bill. A higher basis means higher taxes. If you think your basis is wrong, you can challenge it — but you need to know what number you are challenging and how your assessor arrived at it.
Key Takeaways
- Your property tax basis is the assessed value your local assessor assigns to your property, and your tax bill is calculated by multiplying this basis by your local tax rate.
- The basis is set by the assessor's office, not by you or the real estate market, and it is updated on a schedule that varies by state — some reassess annually, others every few years.
- You can request a copy of your assessment from your county assessor's office, usually online or by mail, to see what basis they are using.
- If you believe your basis is too high, you can file a formal challenge called an appeal or grievance, but the process and deadline vary significantly by state and county.
How assessors determine your property's basis
Assessors typically start with the sale price of your property. If you bought your home for $250,000, that sale price is often used as the initial basis. However, assessors do not simply use your purchase price forever. They adjust the basis over time based on local market trends, property condition, and changes you make to the building.
Some states use a market value approach, where assessors look at comparable sales in your area — what similar homes sold for recently — and adjust your basis up or down accordingly. Other states use a cost approach, calculating what it would cost to rebuild your home from scratch, then subtracting depreciation. A few states use an income approach, mainly for rental properties, based on the income the property generates.
Assessors also account for physical changes. If you add a room, finish a basement, or install a pool, the assessor may increase your basis. If your roof is in poor condition or your foundation has damage, they may lower it. Some assessors conduct in-person inspections; others work from photographs, public records, and sales data alone.
When and how often your basis is reassessed
Reassessment schedules vary widely by state. Some states reassess every year. Others reassess every two, three, or five years. A few states reassess only when a property changes hands. You can find your state's schedule by contacting your county assessor's office or checking your state's department of revenue website.
Even in states with annual reassessment, the basis does not always change year to year. Assessors often apply a cap — a limit on how much the basis can increase in a single year, typically 2% to 5%. This protects homeowners from sudden, large tax jumps. However, caps reset when a property is sold, so a new owner may see a sharp increase in basis and taxes.
You will receive a notice when your assessment changes. This notice usually arrives in the mail and includes your new basis, the tax rate, and your estimated tax bill. Read this notice carefully — it often includes a deadline for filing an appeal if you disagree with the new basis.
How to find your property's current basis
Your property's basis is public record. The easiest way to find it is to visit your county assessor's website and search by address or parcel number. Most counties now offer online portals where you can view your assessment for free. If your county does not have an online system, you can visit the assessor's office in person or call to request a copy of your assessment.
Your assessment notice — the document you receive in the mail — also lists your basis. If you have received a recent notice, that is the fastest way to find the number. Keep in mind that the basis on an old notice may no longer be current if a reassessment has occurred since then.
When you find your basis, you will also see the assessed value broken down by category. For example, the assessment might list the value of the land separately from the value of the building. Some assessments also note whether any exemptions (such as a homestead exemption) have been applied, which can lower your taxable basis.
Challenging your property tax basis
If you believe your basis is too high, you have the right to challenge it. The process is called an appeal, grievance, or formal objection, depending on your state. You typically file this challenge with your county assessor's office or a separate board of assessment review.
To file a challenge, you will need to submit a written request by a specific deadline — often 30 to 60 days after you receive your assessment notice. You must include evidence that your basis is wrong. Common evidence includes recent appraisals, comparable sales of similar homes in your area, photographs showing property damage or poor condition, or documentation of missing features (such as a missing garage or bathroom).
The assessor's office will review your evidence and either agree to lower your basis or deny your request. If they deny it, you may have the right to appeal to a higher board or to court, but this process varies by state and often requires hiring a property tax attorney or appraiser, which costs money.
How basis affects your tax bill and future sales
Your property tax basis directly determines your annual tax bill. A basis of $400,000 with a 1% tax rate costs you $4,000 per year. A basis of $350,000 at the same rate costs $3,500. Over time, small differences in basis add up to hundreds or thousands of dollars in taxes.
Your basis also matters when you sell. In most states, the sale price of your home becomes the new owner's basis. However, in a few states with strict assessment caps, a new owner's basis may be lower than the purchase price, which means they pay less in property taxes than you did — even though they paid more for the house. This is one reason why assessment practices matter to both current and future homeowners.
If you are planning to buy a home, you can ask the seller or the assessor's office what the current basis is and what the property taxes are. This gives you a realistic picture of what your annual costs will be after you purchase.
Frequently Asked Questions
Is my property tax basis the same as the purchase price?
Not necessarily. The purchase price is often used as the starting basis, but assessors adjust it over time based on market conditions, property changes, and local assessment practices. After a few years, your basis may be higher or lower than what you paid.
Can my basis go down?
Yes. If your property loses value due to market decline, neighborhood changes, or physical damage, the assessor may lower your basis during the next reassessment. You can also request a reduction if you have evidence that your basis is too high.
What happens to my basis if I make home improvements?
Most improvements — adding a room, new roof, updated kitchen — increase your basis because they add value to the property. However, routine maintenance like painting or replacing worn carpet typically does not. Ask your assessor which improvements trigger a basis increase in your area.
How do I know when my basis will be reassessed?
Contact your county assessor's office or check their website for your state's reassessment schedule. Some states reassess annually; others every few years. You will receive a notice before or after each reassessment that shows your new basis.
What if I disagree with the assessor's basis but miss the appeal deadline?
Deadlines for appeals are strict and vary by state. If you miss the deadline, you may lose your right to challenge that year's assessment. However, you can usually file an appeal the following year when a new assessment is issued. Contact your assessor's office immediately if you think you have missed a deadline — some jurisdictions have limited exceptions.