Your Property Taxes Are Probably Wrong: How to Appeal and Save $1,000 to $3,000 Every Year

You opened your property tax bill, and the number looked wrong. Not “forgot about the garbage collection surcharge” wrong. More like “did they accidentally add a swimming pool to my records” wrong.

You are not imagining things. According to the National Taxpayers Union Foundation, between 30% and 60% of all taxable property in the United States is over-assessed. That means your county may be charging you too much in property taxes, and the fix costs nothing but a few hours of your time.

The average successful property tax appeal saves homeowners $1,000 to $3,000 per year. Over a decade, that adds up to $10,000 to $30,000 or more, depending on your area and how far off your assessment is. And the appeal process? It is free in most jurisdictions.

Let’s walk through how assessments work, how to check yours, and exactly how to file an appeal.

Want to see this in action? Try the Property Tax Appeal Estimator and get personalized results in seconds.

How Property Tax Assessments Actually Work

Every few years (annually in some states, every two to four years in others), your county assessor’s office determines the value of your property. They use this assessed value to calculate how much you owe in property taxes.

The formula is simple:

Assessed Value x Tax Rate = Annual Property Tax

A home assessed at $400,000 with a 1.5% tax rate owes $6,000 per year. If that home should actually be assessed at $350,000, the fair tax would be $5,250 per year. That is $750 walking out the door every year for no reason.

Mass appraisal: the system behind your assessment

County assessors do not visit every home individually. They use a process called mass appraisal, where computer models estimate property values using data points like square footage, lot size, year built, recent sales in the area, and general neighborhood conditions.

Mass appraisal works well for pricing a neighborhood in broad strokes. It fails at capturing the details that make individual homes different: the house next door that got a $60,000 kitchen renovation, the drainage issue on your lot, the busy road at the end of your driveway, or the market shift that happened after the data was collected.

This is why assessments are so often wrong. The system was never designed to be precise at the individual property level. It was designed to be efficient at the municipal level.

Why 30 to 60% of Properties Are Over-Assessed

The National Taxpayers Union Foundation has tracked assessment accuracy for decades, and their data consistently shows that a large share of residential properties are assessed above their actual market value. Several factors drive this:

Stale data. In states that reassess every two to four years, your assessment may be based on market conditions that no longer exist. If your neighborhood cooled off since the last assessment cycle, your tax bill does not reflect that.

Uniform models miss local variation. A mass appraisal model treats all 1,800 square foot colonials in a zip code roughly the same. But the one backing up to the highway and the one on the quiet cul-de-sac are not the same.

Errors in property records. Incorrect square footage, a finished basement that does not exist, an extra bathroom that was counted by mistake. These data errors are more common than most homeowners realize. The International Association of Assessing Officers (IAAO) acknowledges that property record errors are a leading cause of inaccurate assessments.

Assessment caps create inequity. In some states, assessment increases are capped (California’s Proposition 13 is the most famous example). When values rise unevenly, some homeowners end up paying a disproportionate share of the tax burden while others benefit from artificially low assessments.

Downturns take time to reflect. When the market drops, assessed values often lag behind. Your home may have lost value, but your assessment still reflects the higher number because the reassessment cycle has not caught up.

How to Check if Your Assessment Is Wrong: 3 Steps

Before you file anything, you need to know whether your assessment is actually too high. Here is how to check in about 30 minutes.

Step 1: Find your current assessed value

Go to your county assessor’s website (search “[your county] property assessor” or “[your county] property tax lookup”). Look up your property by address. Note the assessed value and check the property details: square footage, number of bedrooms and bathrooms, lot size, year built.

Compare the property details to what you actually have. If the county says your house is 2,400 square feet and it is actually 2,100, you already have grounds for a correction.

Step 2: Check recent comparable sales

Go to Zillow or Redfin and filter for “Sold” listings within 0.5 miles of your home, sold within the last six months. Look for homes with similar square footage (within 20%), similar lot size, and similar age and condition.

Write down the sale prices of three to five comparable homes. These are your “comps,” and they are the backbone of any successful appeal.

Step 3: Calculate the gap

If your assessed value is more than 10% higher than the average of your comparable sales, you likely have a strong case for appeal. Even a 5% to 10% gap may be worth pursuing, depending on your tax rate.

For example: if your comps sold for an average of $340,000 and your assessment is $400,000, that is a 15% gap. At a 1.5% tax rate, you are overpaying roughly $900 per year.

Use our Property Tax Appeal Estimator to run the numbers for your specific situation.

The Appeal Process, State by State

Every state handles property tax appeals slightly differently, but the general structure is remarkably consistent. Most states offer a two-step process: an informal review followed by a formal appeal if the informal review does not resolve the issue.

Informal review (start here)

Most counties allow you to request an informal review of your assessment before you file a formal appeal. This usually means scheduling a meeting or phone call with the assessor’s office, where you present your evidence and ask them to reconsider.

Informal reviews are free, fast, and often successful. Many homeowners get their assessment reduced at this stage without ever filing a formal appeal. In Cook County, Illinois, roughly 30% of informal review requests result in a reduction, according to county data.

Formal appeal

If the informal review does not work, you file a formal appeal with your county’s Board of Review, Board of Equalization, or Appraisal Review Board (the name varies by state). This typically involves:

1. Filling out a one-page appeal form
2. Attaching your comparable sales evidence
3. Submitting by the deadline (usually 30 to 90 days after your assessment notice)
4. Attending a brief hearing (15 to 30 minutes) if required

Filing fees range from $0 in most states to $25 to $50 in a few. The process is designed to be accessible to homeowners without legal representation.

State-specific highlights

Texas has one of the most homeowner-friendly appeal systems. The appraisal district must prove your value is correct, not the other way around. Success rates are high, often exceeding 50% for residential appeals. Homeowners can also file online in many counties.

Illinois (especially Cook County) sees extremely high appeal volumes and correspondingly high success rates. The county even publishes guides to help homeowners file.

New Jersey requires you to prove your assessment exceeds the “common level range” by a certain threshold. The process is more technical, but the potential savings are significant given the state’s high tax rates.

New York varies by municipality. New York City has its own Tribunal system, while suburban counties have Boards of Assessment Review with different deadlines and procedures.

California operates under Proposition 13, which caps assessment increases at 2% per year. Appeals are still possible if your market value dropped below the Prop 13 value.

Building Your Case with Comparable Sales

The single most important piece of evidence in a property tax appeal is comparable sales data. Assessors and review boards respect hard numbers more than any other argument.

What makes a strong comp

A strong comparable sale is a property that is similar to yours and sold recently in your area. Specifically:

• Location: Within 0.5 miles of your property, ideally in the same subdivision or neighborhood
• Recency: Sold within the last 6 months (12 months at the outside)
• Size: Within 20% of your home’s square footage
• Style: Same general type (ranch, colonial, split-level, etc.)
• Condition: Similar age and maintenance level
• Lot: Similar lot size

How many comps do you need?

Three to five comps is the standard. One comp is not enough because reviewers want to see a pattern. More than five starts to dilute your argument unless every single one supports your case.

Where to find them

• Zillow (zillow.com): Filter by “Sold” listings. Zillow shows sold prices, square footage, and property details for most markets.
• Redfin (redfin.com): Often has more detailed sold data, including price per square foot and days on market.
• County assessor website: Many counties publish recent sales data and assessment records for all properties.
• MLS data: If you have a real estate agent willing to pull comps for you, MLS data is the gold standard.

Presenting your evidence

Create a simple comparison sheet. For each comp, list the address, sale date, sale price, square footage, lot size, and key features. Then show the average sale price of your comps alongside your assessed value. Let the numbers make the argument.

Informal vs. Formal Appeal: Which to Use

Always start with the informal process if your county offers one. Here is why:

Informal review is faster (often resolved in one meeting), free, and does not require formal documentation. If the assessor agrees your evidence is compelling, they can adjust your value on the spot. There is no downside to trying the informal route first.

Formal appeal is your backup if the informal process fails or is not available. It adds structure and accountability: you get a hearing before an independent board, your evidence goes on the record, and the board must issue a formal decision. In some states, a formal appeal is also a prerequisite for taking your case to tax court if you want to escalate further.

One important note: in most states, filing a formal appeal cannot result in your assessment going up. The worst outcome is that your current assessment stands. This is a common misconception that stops people from filing.

Hiring a Tax Appeal Firm vs. DIY

You will see advertisements for property tax appeal services that offer to handle the entire process for you. These firms typically charge 25% to 50% of the first year’s savings as their fee, and they only charge if they win.

When DIY makes sense

If your case is straightforward (clear comps showing your assessment is too high, no unusual property characteristics), you can absolutely handle this yourself. The forms are simple, the process is designed for homeowners, and the evidence is the same whether you present it or a professional does.

For most homeowners with a clear 10%+ gap between assessed value and market value, DIY is the right call. Your total time investment is 4 to 6 hours.

When a professional might be worth it

Consider hiring a firm if your property is unusual (waterfront, historic, commercial/residential mixed use), if you are dealing with multiple properties, or if your state has a particularly complex appeal process. Some states, like New York, have more procedural requirements that professionals can navigate more efficiently.

Also consider a firm if you simply do not have the time. Paying 25% to 50% of one year’s savings is still a good deal when the alternative is letting the overpayment continue year after year.

When NOT to Appeal

Not every homeowner should appeal. There are situations where filing makes no sense or could even backfire:

Your assessment is at or below market value. If comparable sales suggest your home is worth $420,000 and your assessment is $400,000, you are already getting a favorable deal. Filing an appeal draws attention to your property and could theoretically result in a reassessment closer to market value. (This is rare, but why poke the bear?)

You recently made significant improvements. If you added a $50,000 addition or finished your basement, your higher assessment may be accurate. Focus on making sure the assessment reflects only the actual improvements, not inflated estimates.

The gap is tiny. If your assessment is 2% to 3% above market value, the potential savings may not justify the time investment. Run the numbers: at a 1% tax rate, a 3% overassessment on a $300,000 home is only $90 per year.

Your deadline has passed. Every state has strict filing deadlines, usually 30 to 90 days after your assessment notice is mailed. If you missed the window, you will need to wait until next year.

Here’s the Thing

Studies show 30 to 60% of residential properties are over-assessed. Your county assessor uses mass appraisal techniques that can miss renovations to neighboring homes, lot irregularities, or market shifts in your micro-neighborhood. The appeal process is free in most jurisdictions, takes a few hours total, and succeeds 30 to 50% of the time nationally. In states like Texas and Illinois, success rates are even higher (up to 65%).

What I’d Actually Do

Pull up your property’s assessed value on your county assessor’s website right now. Compare it to recent sold prices of similar homes on Zillow. If there is a gap of 10% or more, file an appeal. The form is usually one page. Attach 3 to 5 comparable sales printouts. That is it. If your county has an informal review process, start there because it is faster and often resolves the issue without a formal hearing.

If you want to see the math for your specific situation, use our Property Tax Appeal Estimator. Plug in your assessed value, your estimated market value, and your tax rate. It will show you exactly how much you are overpaying and what a successful appeal could save you over 10 years.

Frequently Asked Questions

How long does a property tax appeal take?

The entire process typically takes 2 to 4 months from filing to decision. Your time investment is about 4 to 6 hours total: a couple hours researching comps, 15 to 30 minutes filing the paperwork, and potentially 1 to 2 hours at a hearing.

Can my taxes go UP if I appeal?

In most states, no. The review board can only consider whether your assessment should go down. They cannot raise your assessment as a result of your appeal. However, check your state’s specific rules, as a small number of jurisdictions allow upward adjustments.

Do I need a lawyer to appeal my property taxes?

No. The process is designed for homeowners to handle on their own. You do not need a lawyer, a professional appraiser, or a tax consultant. Comparable sales data and a simple one-page form are usually all you need.

How often can I appeal?

In most states, you can appeal every year after you receive your new assessment notice. Some homeowners make it an annual habit, especially in states with frequent reassessments.

What if I just bought my home?

Your purchase price is strong evidence of market value. If you bought your home for $350,000 and the county assesses it at $400,000 the following year, your closing documents are powerful evidence for an appeal.

Does a successful appeal affect future assessments?

Yes, typically in your favor. A reduced assessment becomes the new baseline for future years. In states with assessment caps, this can lock in a lower starting point that benefits you for years to come.

What is the deadline to file a property tax appeal?

Deadlines vary by state and county, but most fall within 30 to 90 days of your assessment notice being mailed. Check your county assessor’s website or call their office to confirm the exact deadline for your jurisdiction. Missing the deadline means waiting until next year.

This guide is for informational purposes only and does not constitute legal or tax advice. Property tax laws and appeal procedures vary by state and municipality. Consult a licensed tax professional or attorney for advice specific to your situation.