How to Appeal Your Property Tax Assessment (And Actually Win)
Think your property tax bill is too high? You can appeal your assessment. Here is how the process works in Illinois and Wisconsin and what you need to make a strong case.
Property taxes in Illinois are among the highest in the country. According to propertytaxsolutions.com, the state's average effective rate sits around 2.08% of home value. For a $300,000 house, that is $6,240 per year. If your assessment is off by even 10%, you could be overpaying by hundreds of dollars every single year.
The good news is that you can challenge it. The appeal process is not complicated, but it does take some preparation. This guide walks you through what a property tax assessment is, how to know if yours is wrong, and exactly how to file an appeal in Illinois and Wisconsin.
What Is a Property Tax Assessment?
Your local assessor assigns a value to your property. That assessed value is then used to calculate how much you owe in property taxes. In Illinois, counties do not always assess at full market value. Cook County, for example, assesses residential properties at 10% of their estimated market value before applying the state equalizer and local tax rates.
The problem is that assessors are working with limited information and large volumes of properties. Mistakes happen. Your assessment might reflect outdated data, wrong property characteristics, or values that simply do not match what comparable homes are actually selling for.
How to Tell If Your Assessment Is Too High
Before you file anything, you need to know whether you actually have a case. There are two primary ways to check.
Check Comparable Sales
Look at what similar homes in your area sold for in the recent past, typically the year before the assessment date. If your assessed value implies a market value higher than what comparable homes are selling for, that is a meaningful discrepancy.
You can find recent sales data through your county assessor's website, the Illinois Department of Revenue property transfer data, or public real estate sites.
Check Your Assessment Ratio
In Illinois, there are rules about how assessments should relate to market value. If your county is supposed to assess at a certain percentage and your assessment implies a much higher ratio than your neighbors, that is also grounds for appeal. Your county assessor's office is required to publish assessment notices that include the basis for the valuation. Review it carefully.
The Illinois Property Tax Appeal Process
Illinois gives property owners multiple levels at which to appeal. You do not have to win at the first level to keep going.
Step 1: Appeal to the Township Assessor
This is the starting point in most Illinois counties outside Cook. When you receive your assessment notice, there is usually a window of 30 days to contact the local township assessor and request a review. This is informal and low-cost. Bring your evidence.
Cook County uses a different structure. Owners in Cook County start with the Cook County Assessor's Office, which opens appeals by township on a rolling calendar throughout the year. Check the Assessor's website for your township's open period.
Step 2: Appeal to the Board of Review
If you are not satisfied with the result from the assessor, the next step is the Board of Review. Every county in Illinois has one. In Cook County, the Cook County Board of Review is a separate elected body that handles residential appeals after the Assessor's window closes.
This is where most homeowners focus their effort. According to data from the Cook County Board of Review, more than 56% of taxpayer appeals filed in Cook County result in a reduction. In 2024 specifically, 39.4% of decided appeals won a reduction through the Board of Review alone, up from 28.4% in 2022.
Deadlines vary by county and by township within Cook County. You need to verify the open period for your specific property each year. Missing the window means waiting until the next assessment cycle.
Step 3: Illinois Property Tax Appeal Board (PTAB)
If you lose at the Board of Review and still believe your assessment is wrong, you can escalate to the Illinois Property Tax Appeal Board, known as PTAB. This is a state-level administrative body. PTAB hearings are more formal than local board appeals and typically take longer to resolve, but they are an option for significant disputes.
Step 4: Circuit Court
The final escalation is filing a tax objection complaint in the circuit court of your county. This is where you would typically work with a tax attorney. It is also the most expensive route.
The Wisconsin Appeal Process
In Wisconsin, property tax appeals go through the local Board of Review, which meets annually after assessment notices are mailed. Each municipality sets its own schedule, but most Boards of Review convene in May or June.
To appeal in Wisconsin, you must file a completed objection form before the Board of Review convenes in your municipality. You cannot simply show up without filing first. Once filed, you present your evidence at a scheduled hearing.
If you are not satisfied with the Board of Review's decision, you can appeal to the Wisconsin Department of Revenue or file a claim in circuit court.
As in Illinois, deadlines vary by municipality. Verify the exact dates for your property's jurisdiction directly with your local assessor's office.
What Evidence Makes a Strong Case
Showing up without documentation rarely works. Here is what actually moves the needle.
Comparable sales data. Pull three to five recent sales of properties similar to yours in terms of size, age, condition, and location. This is the single strongest piece of evidence in most appeals. Present the data in a clear, organized format.
An independent appraisal. A certified appraisal from a licensed appraiser carries significant weight, especially at the Board of Review level or above. It is not free, typically running $300 to $600, but it can be worth it if the potential savings are large enough.
Evidence of incorrect property characteristics. If the assessor has the wrong square footage, the wrong number of bedrooms, or does not account for physical problems with the property, document it with photos, a survey, or a contractor's estimate.
Recent purchase price. If you purchased the property recently at arm's length and the assessed value is significantly higher than what you paid, that is direct evidence. Bring the closing documents.
How Much Can You Actually Save?
Nationally, according to appealdesk.com, successful appeals reduce assessed values by an average of 10% to 15%, translating to roughly $1,000 to $3,000 per year in tax savings. In a high-tax state like Illinois, the numbers at the higher end of that range are not uncommon for properties with meaningful overassessments.
Keep in mind that in Cook County, a successful appeal during a reassessment year can lock in the reduced value for up to three years.
When to Hire a Tax Attorney or Consultant vs. Doing It Yourself
For straightforward appeals with clear comparable sales evidence, most homeowners can handle the process themselves at the assessor and Board of Review levels. The filings are not technically complex, and many counties offer step-by-step instructions on their websites.
Consider hiring a professional when:
The potential savings are large enough to justify the cost
You are escalating to PTAB or circuit court
The property type is commercial or mixed-use
You lack time to gather and organize evidence
Your situation involves unusual property characteristics that require expert interpretation
Tax consultants often work on a contingency basis, taking a percentage of the first year's savings. Tax attorneys typically charge hourly. If you hire a contingency firm, confirm in writing exactly what percentage they take and for how many years.
One More Thing: Set a Reminder
Assessment appeals are time-sensitive. Deadlines are set by local jurisdictions, and missing the window means waiting another full cycle. Once you know your county's schedule, put a recurring reminder on your calendar so you review your assessment notice every year.
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