The Three-Part Formula Behind Your Bill
Every property tax bill comes down to three factors working together: assessed value, the mill rate (also called the tax rate or levy rate), and any applicable exemptions. Local governments — typically counties or municipalities — control each of these levers, which is why two neighboring counties can produce very different bills for homes of similar value.
The basic calculation looks like this: take your property's assessed value, subtract any exemptions you qualify for, then multiply the remaining taxable value by the local mill rate. The result is your annual property tax bill. Understanding what moves each of those inputs helps you anticipate changes and spot potential errors.
$3,000+
Median annual U.S. property tax paid
According to U.S. Census Bureau data, median real estate taxes paid by homeowners exceed $3,000 per year nationally, though amounts vary widely by state and county.
0.3%–2.5%
Effective property tax rate range across U.S. states
Effective rates (tax as a share of home value) vary dramatically by state, from under 0.5% in some low-tax states to over 2% in higher-tax jurisdictions, per publicly available state tax data.
~40%
Share of local government revenue from property taxes
The Lincoln Institute of Land Policy has estimated that property taxes account for roughly 40% of local government own-source revenue, making them a primary funding mechanism for schools and services.
How Assessed Value Is Determined
Your local tax assessor's office is responsible for estimating the value of every taxable property in the jurisdiction. This assessed value is not always the same as your home's market value — in many states, assessors apply a fixed ratio (called an assessment ratio) to market value. For instance, a jurisdiction might assess homes at 80% of estimated market value.
Assessors use several approaches to estimate value: sales of comparable homes nearby, the cost to replace the structure, or income potential for investment properties. Residential homes are most commonly valued using recent comparable sales. For a deeper look at the factors that shape a home's estimated value, see what drives a home's appraised value.
Reassessments happen on different schedules depending on where you live — annually in some states, every several years in others. A rising local market means assessed values often climb at reassessment, even for homeowners who haven't touched their property.
Mill Rates and How Local Budgets Drive Your Bill
The mill rate is set each year by local taxing authorities — school districts, counties, and municipalities — based on how much revenue they need to fund public services. One mill equals $1 of tax per $1,000 of assessed value. A property assessed at $250,000 subject to a 20-mill rate would carry a base tax of $5,000 before exemptions.
Most properties fall under multiple taxing jurisdictions simultaneously. Your total mill rate may be the sum of a county rate, a school district rate, a municipal rate, and possibly others. Each body sets its own levy independently, which is why understanding the breakdown on your bill can reveal which service areas are driving increases.
Check Your Property Record for Errors
Before your next assessment cycle, request your property record card from the assessor's office — it lists the characteristics used to value your home, such as square footage, bedroom count, and condition. Errors in these details can inflate your assessed value unnecessarily. Catching a mistake early gives you strong grounds for an appeal.
Exemptions That Can Reduce What You Owe
Exemptions reduce your taxable assessed value — the number the mill rate is actually applied to. The most common is the homestead exemption, available in most states to owners who occupy a property as their primary residence. A $50,000 homestead exemption on a $300,000 assessed value means you only pay tax on $250,000.
Additional exemptions exist for seniors, veterans, people with disabilities, and agricultural land, among others. These vary significantly by state and locality in both eligibility requirements and dollar amounts. Importantly, most exemptions are not applied automatically — you typically need to submit an application to your assessor's office, and deadlines are strict. Missing the filing window often means waiting another full year.
Property taxes represent a significant slice of the ongoing cost of homeownership. For a complete picture of annual expenses beyond the mortgage, see the true annual cost of owning a home.
When and How to Question Your Assessment
Assessors handle thousands of properties, and errors do occur — a wrong square footage, an uncredited exemption, or a comparable sale that doesn't reflect your neighborhood's nuances. If your assessed value appears higher than what similar nearby homes would support, you have the right to appeal.
Most jurisdictions publish an appeal window that opens shortly after assessment notices are mailed — typically 30 to 90 days. Missing this deadline generally means waiting until the next assessment cycle. Evidence that strengthens an appeal includes recent sales of genuinely comparable homes, a recent independent appraisal, and documentation of any property condition issues the assessor may not have accounted for. Our practical walkthrough for challenging a property tax assessment covers the typical steps in detail.
