Your property tax assessed value is the taxable figure your local government assigns to your home, and it’s calculated by multiplying the assessor’s estimate of your property’s market value by your jurisdiction’s assessment ratio. If your home has a market value of $300,000 and your area uses a 40% assessment ratio, your assessed value is $120,000. That number is then multiplied by the local tax rate to produce your annual bill. When the figure comes in too high, you have the right to challenge it, and roughly 40 to 60 percent of homeowners who file a formal appeal walk away with a reduction.
How the Assessed Value Is Calculated
Every property tax bill starts with two numbers. The first is the market value, which is the assessor’s estimate of what your property would sell for in a normal transaction between a willing buyer and seller. The second is the assessment ratio, a percentage set by your jurisdiction that converts market value into a taxable figure. Some jurisdictions assess at 100% of market value, so a home worth $400,000 has an assessed value of $400,000. Others use a fraction. At 10% or 20%, that same home carries an assessed value of $40,000 or $80,000 depending on where you live.
This is why comparing your assessed value directly to a neighbor’s sale price can mislead you. A home that just sold for $500,000 in a jurisdiction with a 15% assessment ratio would carry an assessed value of only $75,000. The ratio itself is not something you can challenge, because it applies uniformly across your jurisdiction. What you can challenge is the assessor’s estimate of your property’s market value, and that is where errors most commonly appear.
How the Assessed Value Turns Into a Tax Bill
Once you have your assessed value, the local tax rate (often called the millage rate or mill levy) determines your actual bill. A mill is one-thousandth of a dollar, so a rate of 50 mills means you pay $50 for every $1,000 of assessed value. Divide the millage rate by 1,000 and multiply by your assessed value. At 50 mills, a home with an assessed value of $120,000 owes $6,000 in property tax.
Your total millage rate is actually a stack of separate levies from every taxing entity that covers your property: the county, the municipality, the school district, the fire district, the library, and so on. Each entity sets its own rate, and your bill reflects all of them combined. Two homes with identical assessed values in the same county can carry noticeably different bills if one falls inside a city or special district and the other doesn’t. This matters because a successful assessment appeal reduces your tax across every one of those levies at once, not just one.
Growth Caps and What Triggers a Reassessment
Many states limit how much your assessed value can climb from year to year, even when market value is rising faster. California’s cap is the most well-known at 2% per year. Florida caps homestead value increases at 3%, and states like New York and South Carolina restrict total assessment growth over five-year periods. These caps exist to keep longtime homeowners from being taxed out of their homes during real estate booms.
The catch is that most caps reset when a property changes hands. Buy a home the previous owner held for 20 years, and the assessed value may jump significantly to reflect the current market price. Newer buyers in capped states frequently pay more property tax than neighbors in comparable homes who bought years ago. Two other events commonly trigger reassessment: finishing new construction and completing major renovations. Adding a bedroom, building a deck, or finishing a basement typically triggers reassessment of the improvement’s value. Routine maintenance such as repainting, replacing a roof with similar materials, or fixing a furnace generally does not.
Check Your Exemptions Before You Do Anything Else
Before disputing an assessed value, make sure you’re already receiving every exemption you qualify for. Missing an available exemption is one of the most expensive property tax mistakes, and you can fix it with a simple application rather than a formal appeal.
A homestead exemption is available in most states and reduces the assessed value of your primary residence by a fixed dollar amount, ranging roughly from $1,000 to $100,000 depending on the state. You typically need to own and occupy the property as your primary home, and you must file an application with the assessor’s office. It’s rarely automatic. Many states set a filing deadline in early spring for the upcoming tax year.
Senior exemptions target homeowners age 65 and older, often with an income ceiling. Some states freeze the assessed value entirely so it never increases. Others apply a flat reduction or a refundable credit. Income limits vary widely, from $37,000 in some states to over $500,000 in others.
Veteran and disability exemptions are available in many states for veterans with a service-connected disability. A 100% disability rating typically qualifies for the largest exemption, though some jurisdictions extend partial relief to veterans with any compensable disability rating.p>
Programs and deadlines differ enough from state to state that only your local assessor’s office or county website will give you the accurate specifics. The application is usually a one-page form, and once approved, many exemptions renew automatically each year.
Pull Your Property Record Card and Look for Errors
The single best thing you can do before deciding whether to appeal is pull up your property record card. This document, available from your county assessor’s office and often online, contains every data point the assessor used to value your home: lot size, total square footage, number of bedrooms and bathrooms, year built, construction quality, and any listed features such as a finished basement, swimming pool, or detached garage. Each property has a unique parcel number you’ll need for any filings.
Errors on the record card are more common than most homeowners expect. Multi-story homes are particularly prone to incorrect square footage because upper floors are sometimes measured wrong or double-counted. Other frequent mistakes include listing a garage that was demolished, counting a half-bath as a full bath, recording a finished basement when it’s unfinished, or using an incorrect lot size. Any of these can inflate your assessed value by thousands of dollars.
Walk through your home with the record card in hand and compare every line item to reality. If something doesn’t match, you already have grounds for a correction, and in many cases the assessor’s office will fix a factual error administratively without requiring a formal appeal.
Building a Case With Comparable Sales
If the record card is accurate but you still believe your home is overvalued, comparable sales are your strongest evidence. The assessor valued your property by looking at what similar homes in your area sold for, so the most effective way to challenge that conclusion is to show the sales data points in a different direction.
Start by identifying homes that sold recently and share key characteristics with yours: similar square footage, lot size, age, construction quality, number of bedrooms and bathrooms, and location within the same neighborhood or school district. Sales within the past 12 months carry the most weight, and the closer the properties are to yours geographically, the more persuasive they’ll be. Aim for at least three to five strong comparables.
Raw sale prices aren’t enough on their own. You need to account for differences between each comparable and your property. If a comparable home has a pool and yours doesn’t, the sale price should be adjusted downward to reflect what it would have sold for without the pool. If your home has an extra bedroom, adjust upward. Calculating a price per square foot of living area for each comparable (sale price divided by livable square footage, excluding garages and porches) gives you a quick way to compare across properties with slightly different sizes. Drive by each comparable and take photos. A board reviewing your appeal will want to see that the homes are genuinely similar, and photos showing condition differences can be persuasive.
One thing that trips up a lot of homeowners: the sales you use as evidence need to be arm’s-length transactions. A sale between family members, a foreclosure, or a quick sale under financial pressure doesn’t reflect what the market would actually pay. Stick to conventional, open-market sales where both sides negotiated freely.
Filing the Appeal
Start With an Informal Review
Before filing anything formal, call or visit your assessor’s office and ask for an informal review. Many jurisdictions offer this as a first step, and it’s often the fastest path to a correction. Bring your property record card, any errors you’ve found, and your comparable sales. An informal conversation with the assessor may resolve the issue on the spot, especially if the problem is a factual mistake rather than a judgment call about value. An informal review is not required in most places, so if the assessor isn’t receptive, you can skip straight to the formal process.
The Formal Filing
Your official notice of assessment arrives by mail each year and includes your assessed value, the deadline to file an appeal, and instructions for how to do it. That deadline is strict and usually falls 30 to 45 days after the notice date. Miss it, and you’re locked in for the full tax year regardless of how strong your case is.
Filing typically requires a specific appeal form, available from the assessor’s office or downloadable from your county’s website. You’ll need your parcel number, the current assessed value you’re challenging, the value you believe is correct, and the evidence supporting your position. Some jurisdictions accept filings online. Others require submission by mail or in person. Filing fees range from roughly $15 to $300 depending on where you live.
The Hearing
After filing, expect to wait 60 to 120 days before your case is heard by a Board of Equalization, assessment review board, or similar local body. The panel is typically made up of appointed officials who are independent of the assessor’s office.
Here’s the part most people don’t realize going in: you carry the burden of proof. The assessor’s valuation is presumed correct, and it’s on you to present enough evidence to overcome that presumption. Showing up and saying “my taxes are too high” accomplishes nothing. Present your comparable sales analysis, point out any errors on the record card, and explain specifically why the assessor’s market value estimate is wrong. You can present your case yourself or hire a representative, often a property tax consultant or attorney, to do it for you. Professional representation tends to improve success rates. For straightforward cases built on clear factual errors or strong comparables, presenting your own case is entirely reasonable.
The Decision and What Comes Next
The board issues a written decision, usually within a few weeks of the hearing, explaining whether your assessed value will be reduced or maintained. If you win, the reduction applies to the current tax year, and you’ll either receive a refund or a credit on your next bill. A successful appeal typically reduces assessed value by 10 to 15 percent.
If the board rules against you, most states allow a further appeal to a state tax court or equivalent judicial body. This level is more formal, closer to an actual courtroom proceeding, and the cost and complexity go up accordingly. For most homeowners, the administrative hearing is the practical endpoint. If a significant amount of money is at stake and you have strong evidence the board ignored, the tax court option exists.
What Happens If You Don’t Pay
Ignoring a property tax bill sets off consequences that escalate faster than most people expect. Penalties and interest start accruing almost immediately after the due date, and rates vary by jurisdiction but can add 10 to 20 percent or more to the balance within the first year. The longer you wait, the more expensive the problem becomes.
If the balance remains unpaid, your local government will eventually place a tax lien on the property. A tax lien takes priority over nearly all other claims, including your mortgage. The government can then sell that lien to an investor or proceed directly to a tax sale of the property itself. In most states, you get a redemption period after the sale, typically one to two years, during which you can reclaim the property by paying the full amount of unpaid taxes plus all accumulated penalties, interest, and costs. Some states offer no redemption period at all, meaning the sale is final.
One important protection: in 2023, the U.S. Supreme Court ruled that a government cannot keep surplus proceeds from a tax sale beyond what the homeowner actually owed. If your home is sold at a tax sale for $200,000 but you only owed $15,000 in back taxes and fees, the remaining $185,000 belongs to you, not the government.1Supreme Court of the United States. Tyler v. Hennepin County, Minnesota (2023)