What real estate tax is and how assessors calculate it
Real estate tax is a yearly property tax you pay to your local government based on what your home or land is worth. The amount you owe depends on three things: the assessed value of your property, the tax rate in your area, and any exemptions you may have. The basic formula is: assessed value × tax rate = your annual tax bill.
Your local assessor's office determines the assessed value, which is usually a percentage of the property's market value — not necessarily what you paid for it or what it would sell for today. That percentage varies by state and county. The tax rate, called the millage rate, is set by your local government and expressed as dollars per $1,000 of assessed value. A rate of 15 mills means you pay $15 in tax for every $1,000 of assessed value.
The assessed value is not the same as the market value. An assessor looks at recent sales of similar properties in your area, the condition of your building, the size of the lot, and local market trends. They update assessments on a schedule that varies by location — some counties reassess every year, others every three to five years. You receive a notice when your assessment changes, and you have the right to challenge it if you believe it is wrong.
Key Takeaways
- Real estate tax is calculated by multiplying your property's assessed value by the local tax rate, which is expressed in mills (dollars per $1,000 of assessed value).
- The assessed value is determined by your local assessor's office and is usually a percentage of market value, not what you paid for the property.
- Tax rates and assessment schedules vary significantly by county and state, so you cannot compare your bill directly to a neighbor's without knowing both properties' assessed values.
- You can challenge your assessment if you believe it is incorrect, and the process and important date for filing an appeal depend on your local assessor's office rules.
- Some properties receive exemptions that reduce the assessed value — homestead exemptions, senior exemptions, and agricultural exemptions are common — but you must request them.
Finding your property's assessed value
Your assessed value appears on your property tax bill, which you receive once or twice a year depending on your county. If you do not have a recent bill, you can find it through your county assessor's website. Most counties now publish assessment records online and searchable by address or parcel number. Search "[your county name] assessor" to find the office website.
When you access the record, you will see the assessed value listed separately from the market value estimate (if the assessor provides one). The assessed value is the number you use in the tax calculation. Some assessor websites also show the breakdown: land value and building value listed separately. This matters if you are trying to understand why your assessment changed or if you plan to appeal it.
If you cannot find your property online or the website is unclear, call your county assessor's office directly. They can tell you the current assessed value, when it was last updated, and when the next reassessment is scheduled. Keep a record of the assessed value and the date you received it, because assessments change and you will need to know which year's value you are working with.
Locating your local tax rate
The tax rate for your property is set by your county or municipality and is usually published on the same assessor's website or on your county's tax collector website. Search "[your county name] tax rate" or "[your county name] millage rate." The rate is often expressed as mills per $1,000 of assessed value, though some areas express it as a percentage.
Tax rates can vary within a county if you live in a school district, fire district, or other special taxing area. Your bill may show multiple rates stacked together — one for the county, one for the school district, one for the fire district — each applied to your assessed value. Add all the rates together to get your total millage rate, then use that in your calculation.
Rates change yearly because local governments set their budgets and adjust rates to meet revenue needs. If you are comparing your tax bill from one year to the next, the rate may have changed even if your assessed value stayed the same. Check both numbers before assuming your bill went up because of a reassessment.
The step-by-step calculation
Once you have your assessed value and your tax rate, the math is straightforward. Divide your assessed value by 1,000, then multiply by the millage rate. For example: if your assessed value is $250,000 and your millage rate is 15 mills, the calculation is ($250,000 ÷ 1,000) × 15 = $3,750 per year.
If your tax rate is expressed as a percentage instead of mills, multiply the assessed value by the percentage. A rate of 1.5% on a $250,000 assessed value would be $250,000 × 0.015 = $3,750. The result is the same; the format is just different.
If your property receives an exemption, subtract the exemption amount from the assessed value before you calculate. A homestead exemption might reduce your assessed value by $50,000, so you would calculate tax on $200,000 instead of $250,000. The exemption lowers the base number, not the rate.
Understanding exemptions and how they reduce your bill
Many states and counties offer exemptions that reduce the assessed value of your property, which lowers your tax bill. The most common is a homestead exemption, which applies if the property is your primary residence. Other exemptions exist for seniors, veterans, people with disabilities, agricultural property, and religious or nonprofit organizations.
Exemptions are not automatic. You must request them from your assessor's office, usually by filing a form and providing proof — a deed showing you own the property, a driver's license showing your address, discharge papers if you are claiming a veteran exemption. The important date to file varies by county, often in the spring or early summer. If you miss the important date, you may have to wait until the next year to claim the exemption.
An exemption reduces the assessed value, not the tax rate. If you have a $50,000 homestead exemption and your assessed value is $250,000, you pay tax on $200,000 instead. The exemption amount varies by state and sometimes by county within a state. Check your assessor's website or call to find out what exemptions you may be may have access to to and what the exemption amount is in your area.
Why your calculated amount might not match your bill
If you calculate your tax using assessed value and tax rate but the number does not match your actual bill, several things could explain the difference. Your bill may include fees that are not part of the property tax calculation — county clerk fees, tax collection fees, or school fees that are added on top. Some bills also show a discount if you pay early, or a penalty if you pay late.
Your assessed value on the bill might be from a different year than the tax rate. If your assessment was updated this year but the rate is from last year, or vice versa, your calculation will be off. Check the date on both numbers to make sure they are from the same tax year.
If you have a mortgage, your lender may be paying your property tax as part of your escrow account, and the amount they pay might differ slightly from what you calculated because they are using different dates or rounding. Your actual bill from the county is the authoritative number; use it to verify your calculation is in the right ballpark, but do not assume your math is wrong if there is a small difference.
Frequently Asked Questions
Is assessed value the same as market value?
No. Assessed value is what the assessor determines your property is worth for tax purposes, usually a percentage of market value. Market value is what the property would sell for on the open market today. The assessed value is typically lower than market value, but not always. Only the assessed value is used to calculate your tax bill.
Can I lower my property tax by lowering the assessed value?
You cannot lower the assessed value yourself, but you can challenge it if you believe it is wrong. If the assessor overestimated your property's value compared to similar homes in your area, you can file an appeal with your assessor's office or your county's board of appeals. You will need to provide evidence — recent sales of comparable properties, a professional appraisal, or documentation of property damage or defects.
What happens if I disagree with my assessed value?
Contact your assessor's office and ask about the appeal process. Most counties have a important date — often 30 to 60 days after you receive your assessment notice — to file a formal challenge. You will need to submit evidence that the assessment is incorrect. If the assessor does not change it, you can appeal to your county's board of appeals or tax assessment review board, depending on your state's process.
Do I have to pay property tax every year?
Yes, property tax is an annual obligation as long as you own the property. If you have a mortgage, your lender typically requires you to pay it through escrow. If you own the property outright, you pay the county directly. Failure to pay results in penalties, interest, and eventually a tax lien on your property.
How often does my assessed value change?
The schedule varies by location. Some counties reassess every year, others every three to five years. A few states reassess only when the property changes hands. Check your assessor's website or call to find out the reassessment schedule in your county and when your property was last assessed.