Property tax starts with your home's assessed value, not what you paid for it
Your property tax bill is not based on the price you paid when you bought the house. Instead, a county or municipal assessor estimates what your property is worth on the open market — this is called the assessed value. The assessor then multiplies that value by a tax rate (also called a millage rate) set by your local government. That multiplication gives you the dollar amount you owe each year.
The formula is straightforward: Assessed Value × Tax Rate = Annual Property Tax. But each piece of that equation varies by location and changes over time, which is why two identical houses in different towns can have very different tax bills, and why your own bill can jump from one year to the next.
Key Takeaways
- Your property tax bill is based on an assessor's estimate of your home's market value, not the price you paid for it.
- The assessed value is multiplied by a tax rate set by your county or municipality to produce your annual bill.
- Assessments happen on different schedules in different places — some yearly, some every three years, some every five years.
- You can usually challenge an assessment if you believe the value is too high, though the process and important date vary by location.
- Some properties receive exemptions or reductions — homestead exemptions, senior exemptions, agricultural exemptions — that lower the taxable value.
How assessors determine your home's value
Assessors use three main approaches, though they do not always use all three for every property. The sales comparison approach looks at recent sales of similar homes in your area — if a house like yours sold for $300,000 six months ago, that sale informs your assessment. The cost approach estimates what it would cost to rebuild your house from scratch, then subtracts wear and tear. The income approach applies mainly to rental properties and calculates value based on the income the property generates.
Most residential assessments rely heavily on the sales comparison method because it reflects what buyers actually pay. Assessors look at square footage, lot size, age, condition, number of bedrooms and bathrooms, recent renovations, and whether the property has a garage or pool. They also account for location — a house on a busy road may be valued lower than an identical house on a quiet street.
Assessors do not visit every property every year. Many use computer models that adjust previous assessments based on new sales data and known changes to the property. If you have made major improvements — added a room, replaced the roof, finished a basement — you should report these to the assessor's office, because they will eventually show up in records anyway and affect your value.
Assessment schedules and when your value can change
How often your property is reassessed depends on where you live. Some counties reassess every year. Others do it every three years, every five years, or only when the property changes hands. A few states use fractional assessment, meaning they assess all properties at a percentage of market value rather than 100 percent — this does not change what you owe, but it explains why your assessed value looks lower than comparable sales prices.
Even if your county reassesses annually, your assessed value may not change every year if the market is stable. But when the market shifts — either up or down — your assessment will eventually reflect it. If your neighborhood has seen rapid appreciation, expect your assessed value to rise. If values have fallen, you may be able to challenge an assessment that is now too high.
The timing of when assessments take effect also varies. Some go into effect January 1, others on July 1, and some on the anniversary of your purchase. Your tax bill for a given year is usually based on the assessment as of a specific date — often called the "assessment date" — which may be months before you receive the bill.
Tax rates and how they are set
The tax rate is set by your local government — usually the county, but sometimes the city, school district, or special district (for fire, water, or library services). These bodies set a budget for the year, calculate how much revenue they need from property tax, and divide that by the total assessed value of all properties in their jurisdiction. The result is the tax rate, expressed as a percentage or as dollars per $1,000 of assessed value.
A rate of 1.2 percent means you pay $1.20 for every $100 of assessed value. A rate of 12 mills means you pay $12 for every $1,000 of assessed value — these are the same thing, just different ways of stating it. Your bill may include rates from multiple taxing bodies stacked together: county rate plus school district rate plus city rate plus special district rate.
Tax rates can change year to year because budgets change. A school district that needs more money for new buildings or teacher salaries will raise its rate. A county that collects more revenue than expected (because property values rose) may lower its rate. You can usually find your local tax rate on your county assessor's website or on your property tax bill itself.
Exemptions and reductions that lower your bill
Many states and localities offer exemptions that reduce the assessed value of certain properties. A homestead exemption reduces the taxable value of a primary residence — the amount varies widely, from a few thousand dollars to 50 percent of the home's value depending on the state. Some states offer larger exemptions to seniors, veterans, disabled persons, or surviving spouses.
Agricultural land often receives a special exemption so that farmland is taxed based on its value as farmland, not its potential value if developed. Some jurisdictions offer exemptions for historic properties, renewable energy installations, or properties in economically distressed areas. To receive an exemption, you typically must file a form with the assessor's office by a specific important date — missing the important date usually means losing the exemption for that year.
Exemptions are not the same as deferrals. Some states allow seniors or disabled homeowners to defer property taxes — meaning you do not pay them now, but the debt is recorded as a lien on the property and comes due when you sell or pass away. Deferrals can be useful if you are house-rich but cash-poor, but they do not reduce what you ultimately owe.
How to challenge an assessment you believe is wrong
If you think your assessed value is too high, most jurisdictions allow you to file a formal challenge, usually called an appeal, a protest, or a reassessment request. The process and important date vary significantly. Some places give you 30 days after receiving your bill; others give you until a specific date each year, often in spring. Missing the important date usually means you cannot challenge that year's assessment.
To file a challenge, you typically submit a form to your county assessor's office or a board of appeals. You will need to explain why you believe the value is wrong — for example, you can provide recent appraisals, comparable sales of similar homes that sold for less, or evidence of property damage or deferred maintenance. Some jurisdictions require you to hire an appraiser; others allow you to submit evidence yourself.
If the assessor agrees your value is too high, they will lower it. If you disagree with their response, you can usually appeal to a county board of appeals or equalization board. A few states allow further appeal to tax court, though this is expensive and most homeowners do not pursue it. Even if you lose the appeal, you have lost nothing except the time spent filing.
Understanding your property tax bill
Your annual property tax bill shows the assessed value, the tax rate or rates applied, and the total amount due. It may also show the previous year's assessment so you can see whether your value went up or down. Some bills break out the portion going to each taxing body — school district, county, city, fire district — so you can see where your money goes.
The bill usually specifies a due date and whether payment is due in one lump sum or in installments. Some jurisdictions allow you to pay in two installments (often in spring and fall); others require full payment by a single date. If you pay late, you will owe a penalty and interest. If you do not pay at all, the jurisdiction can place a lien on your property, and eventually foreclose and sell it to recover the debt.
If you own property in multiple jurisdictions — for example, a house in one county and a rental property in another — you will receive separate bills from each. Each bill is calculated independently using that jurisdiction's assessed value and tax rates.
Frequently Asked Questions
Why did my property tax bill go up when I did not make any improvements?
The most common reason is that your assessed value increased because property values in your area rose. This happens automatically on the assessor's next reassessment cycle, even if you did nothing to your house. Tax rates can also increase if your local government needs more revenue. You can check your assessor's website to see whether your assessed value changed, and by how much.
Can I lower my property tax by disputing the assessed value?
Yes, if you can show the assessor that the value is genuinely too high. You will need evidence such as a recent appraisal, comparable sales of similar homes that sold for less, or documentation of major damage or needed repairs. The process is called an appeal or protest, and you must file by your jurisdiction's important date — usually 30 to 60 days after receiving your bill.
What is the difference between assessed value and market value?
Market value is what your home would sell for today on the open market. Assessed value is the assessor's estimate of that market value, used to calculate your tax bill. They should be close, but assessed values often lag behind actual market changes because assessments are not done every year in every place. Your assessed value may be lower or higher than what your home would actually sell for.
Do I have to pay property tax if I own my home outright?
Yes. Property tax is owed by the owner of record, whether the property is paid off or financed. If you have a mortgage, your lender may require you to pay property tax through an escrow account as part of your monthly payment, but you are still legally responsible for it. If you do not pay, the jurisdiction can place a lien on your property.
How do I find out what my property is assessed at?
Your assessed value appears on your annual property tax bill. You can also search your county assessor's website — most provide free online databases where you can look up any property by address or owner name. The assessor's office can also mail or email you this information if you call or visit in person.