More than 40% of U.S. homes are overassessed. That means nearly half of all homeowners are paying more in property tax than they should. The median potential savings for those who successfully appeal? $539 per year. Not life-changing money, maybe. But over a decade of homeownership, that's $5,390 you handed to your county for no reason.
The average property tax bill on a single-family home hit $4,300 in 2024, a 5.8% jump over the previous year. Collectively, American homeowners paid $382.7 billion in property taxes that year. And the system that calculates what you owe is surprisingly opaque. Most people never question it.
They should.
30-Second Summary: Property tax is based on your home's assessed value multiplied by your local tax (mill) rate. Assessments are frequently wrong. You can appeal yours with comparable sales data, and the process is free in most jurisdictions.
How Property Tax Actually Works
Property tax is an ad valorem tax, meaning "according to value." The more your property is worth (according to the government), the more you pay. Two numbers drive your bill: your home's assessed value and your local mill rate.
That's the entire formula. Everything else is detail.
Assessed Value vs. Market Value
Your assessed value is what your county's tax assessor says your home is worth for taxation purposes. This is not the same as what you could sell it for (market value), and it's not what your bank's appraiser said during your mortgage process.
Many jurisdictions apply an assessment ratio that deliberately sets the assessed value below market value. If your town uses an 80% ratio and your home's market value is $450,000, your assessed value is $360,000.
Here's where things get messy. Assessors don't visit every home every year. Some counties reassess annually. Others do it every three to five years. A few states, like California under Proposition 13, only fully reassess when a property changes hands. Between reassessments, your home's value in the tax system can drift far from reality.
A University of Chicago study found that property tax assessments are frequently regressive, meaning owners of lower-value homes get overassessed at higher rates than owners of expensive ones. The system isn't just imprecise. It can be unfair.
The Mill Rate (And Why 20 Mills Isn't 20%)
The mill rate is your local tax rate. One mill equals $1 in tax for every $1,000 of assessed value. This trips people up because "20 mills" sounds like 20%, but it's actually 2%.
Your local government sets the mill rate each year based on how much revenue it needs to fund schools, roads, fire departments, and parks. Different taxing districts (county, city, school board, special districts) can each add their own mills, stacked on top of each other.
| Component | Mill Rate | What It Funds |
|---|
| County | 8 mills | Roads, sheriff, courts |
| City | 6 mills | Police, parks, zoning |
| School District | 10 mills | Public schools |
| Special District | 1 mill | Library, flood control |
| Total | 25 mills | |
If your assessed value is $360,000 and the combined mill rate is 25:
($360,000 ÷ 1,000) × 25 = $9,000 per year
That's the basic math. But it often gets more favorable from here.
Exemptions That Lower Your Bill
Most states offer exemptions that reduce your taxable value before the mill rate is applied.
Homestead exemption is the most common. If you live in the home (it's your primary residence), you may shave $25,000 to $100,000 off your assessed value, depending on the state. Texas, for instance, offers a $100,000 homestead exemption for school district taxes.
Other common exemptions:
- Senior citizen exemptions (age 62 or 65+, varies by state)
- Veteran/military exemptions (partial or full, especially for disabled veterans)
- Disability exemptions
- Income-based exemptions for low-income homeowners
Here's the thing most people miss: exemptions are not automatic. You have to apply. Your county assessor's office handles applications, and deadlines vary. Miss the deadline, and you pay full freight for the year. I've talked to homeowners who went three years without claiming a homestead exemption simply because nobody told them the form existed.
A Worked Example
Alex owns a home in a town with a mill rate of 25 and an assessment ratio of 80%. The home's fair market value is $450,000.
Step 1: Assessed Value
$450,000 × 0.80 = $360,000
Step 2: Apply Mill Rate
($360,000 ÷ 1,000) × 25 = $9,000
Step 3: Apply Homestead Exemption ($50,000)
New taxable value: $360,000 − $50,000 = $310,000
($310,000 ÷ 1,000) × 25 = $7,750
That $50k exemption saved Alex $1,250 per year. One form. Ten minutes.
Why Your Assessment Might Be Wrong
Between 30% and 60% of taxable property in the U.S. is overassessed, according to the National Taxpayers Union Foundation. Several things cause this:
Stale data. If your county reassesses every three years, your value is based on market conditions from three years ago. Markets shift. Neighborhoods change.
Errors. Assessors sometimes get the square footage wrong, count an extra bathroom, or miss that the "finished basement" is actually unfinished. One wrong checkbox on a data card can add thousands to your bill.
Blanket adjustments. Instead of appraising each property individually, many counties apply percentage increases across the board. If your neighborhood went up 8% on average but your specific block didn't, you're overpaying.
Comparable sale distortion. An assessor might use a recently sold home two streets over as a "comp" for your property, even though that home had a renovated kitchen and yours has original 1990s laminate.
Assessment data is messy. And nobody but you has an incentive to fix it.
How to Appeal Your Property Tax Assessment
This is the section most competitors skip or treat as a footnote. It shouldn't be. In New Jersey alone, county tax boards granted $2 billion in assessment reductions from 15,717 appeals in 2025. That's an average reduction of over $127,000 in assessed value per successful appeal.
Step 1: Get Your Property Record Card
Contact your county assessor's office (many have this online) and request the property record card for your home. This document shows every detail the assessor used: square footage, number of rooms, lot size, condition rating, and comparable sales.
Review it for errors first. Wrong square footage? An extra half-bath that doesn't exist? A condition rating of "excellent" when your roof is 20 years old? These are the easiest wins.
Step 2: Gather Comparable Sales ("Comps")
Find 3 to 5 recently sold homes within a half-mile of yours that are similar in size, age, and condition. If those homes sold for less than your assessed value (adjusted for the assessment ratio), you have a case.
Where to find comps:
- Zillow, Redfin, or Realtor.com "Recently Sold" filters
- Your county's online property records
- A licensed appraiser (costs $300 to $500, but worth it for high-value appeals)
Step 3: Document Property Condition Issues
If your home has problems that reduce its value (foundation cracks, outdated systems, flood zone location), photograph everything. Bring repair estimates if you have them.
Step 4: File the Appeal
Every jurisdiction has a deadline, usually 30 to 90 days after your assessment notice arrives. Filing is typically free. You'll submit your evidence to the local Board of Equalization, Board of Assessment Review, or equivalent body.
Most appeals start with an informal review (a conversation with the assessor). If that doesn't resolve it, you'll get a formal hearing. You don't need a lawyer for most residential appeals, though property tax consultants exist and typically charge a percentage of the savings.
Step 5: Show Up
Bring your comps, your photos, and your property record card with errors highlighted. Be respectful, be organized, and focus on data. "My taxes are too high" isn't an argument. "My assessed value is $40,000 above comparable sales in my neighborhood" is.
One common fear: "Will appealing raise my taxes?" It's theoretically possible if the board finds your home is underassessed, but this is rare. The overwhelming outcome is either a reduction or no change.
Property Tax Rates by State: The Extremes
The spread across states is enormous. Where you live determines more about your tax bill than almost any other factor.
| State | Effective Tax Rate | Avg Tax on Avg-Value Home |
|---|
| New Jersey | 2.23% | $10,485 |
| Illinois | 1.84% | $4,995 |
| Connecticut | 1.41% | $5,838 |
| Texas | 1.38% | $4,237 |
| U.S. Average | 0.86% | $4,300 |
| Colorado | 0.50% | $2,835 |
| Tennessee | 0.46% | $1,483 |
| Alabama | 0.41% | $960 |
| Hawaii | 0.27% | $3,643 |
Source: ATTOM Data Solutions (2024), Tax Foundation (2024)
Notice Hawaii: it has one of the lowest rates (0.27%) but a substantial bill ($3,643) because home values are sky-high. Alabama has a similar rate but an average bill under a thousand dollars because homes cost less. Rate and bill are different conversations.
For a deeper look at how these numbers stack up with insurance, utilities, and maintenance, see our breakdown of the annual cost of owning a home by state.
The Federal Deduction (And Its Limits)
You can deduct property taxes on your federal income tax return, but only if you itemize. The Tax Cuts and Jobs Act capped the state and local tax (SALT) deduction at $10,000 ($5,000 if married filing separately). That cap includes property taxes and state income taxes combined, and it remains in effect through 2025.
For homeowners in high-tax states like New Jersey or New York, this cap is painful. If you're paying $8,000 in state income tax and $10,000 in property tax, you're leaving $8,000 on the table. Congress has debated raising the cap, but as of this writing, $10,000 is the law.
Understanding how marginal tax brackets work can help you estimate the actual dollar value of your deduction.
Your Next Move
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Pull your property record card from your county assessor's website. Check for errors in square footage, room count, and condition rating. This takes 10 minutes.
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Check if you've claimed every exemption you qualify for. Homestead, senior, veteran, disability. Go to your assessor's website or call their office. Applications usually take one page.
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Compare your assessed value to recent sales. Search Zillow or Redfin for 3 to 5 similar homes sold within the last year near yours. If they sold for less than your assessed value, you have grounds to appeal.
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Mark the appeal deadline on your calendar. It's on your assessment notice. Miss it, and you wait another year.
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Use our mortgage calculator to see how a lower property tax bill changes your total monthly housing cost. Even $50/month adds up.
Property taxes aren't optional. But overpaying is.
References
- Realtor.com. (2025). Are Homeowners Overpaying on Property Taxes? Now They Can Find Out on Realtor.com. https://www.realtor.com/research/tax-protest-report-2025/
- ATTOM Data Solutions. (2025). Average Property Tax Amount on Single-Family Homes Up 5.8 Percent Across U.S. in 2024. https://www.attomdata.com/news/market-trends/home-sales-prices/2024-annual-tax-report/
- Tax Foundation. (2025). Property Taxes by State and County. https://taxfoundation.org/data/all/state/property-taxes-by-state-county-2024/
- Berry, C. (2021). Reassessing the Property Tax. University of Chicago Harris School of Public Policy.
- State of Connecticut Office of Policy and Management. (2024). Mill Rates. https://portal.ct.gov/opm/igp/grants/mill-rates
- National Association of Counties. (2024). Property Taxes: A Look at Exemptions, Tax Limits and Assessment Cycles. https://www.naco.org/sites/default/files/documents/Property%20Taxes%20A%20Look%20at%20Exemptions,%20Tax%20Limits%20and%20Assessment%20Cycles.pdf
- Hanover Advisors. (2025). Property Tax Assessment Data. https://www.hanoveradvisorsinc.com
- Fox 29 Philadelphia. (2026). New Jersey Property Tax Appeals Summary. https://www.fox29.com
- Taylor, M. & Probasco, J. (2025). Property Tax Rates by State. Bankrate. https://www.bankrate.com/real-estate/property-tax-by-state/
- Grovehopper. (2025). Property Tax Appeal Guide. https://www.grovehopper.com
- NerdWallet. (2025). Property Tax Deduction: How It Works, Annual Limits. https://www.nerdwallet.com/taxes/learn/property-tax-deduction
