Cook County Property Tax Reassessment: A Guide

In Cook County, properties are evaluated for tax purposes every three years through a process known as triannual reassessment. This applies to all districts within the county, including the City of Chicago, North Suburbs, and South Suburbs. The reassessment schedule follows a rotation, so that in any given year, only one district is being reassessed while the other two districts remain unchanged.

Valuation Process

The reassessment is based on the value of the property as of January 1st of the reassessment year. The Cook County Assessor’s Office evaluates properties using a combination of market data, property characteristics, and income (for commercial properties). They use sales of comparable properties, rental income, and other relevant data to determine the fair market value.


Property owners receive a notice of reassessment, which includes the new assessed value of their property and a comparison with the previous assessment.


If property owners do not agree with the recently assigned valuation, they have the option to challenge it through an appeal process. Appeals can be submitted to the Cook County Assessor’s Office and, if needed, can be further escalated to the Cook County Board of Review.


Once assessments are completed, an equalization factor (also known as the multiplier) is applied to ensure uniform property assessment levels across the county. This factor adjusts assessments to a uniform percentage of market value, as required by state law.

Tax Rates

After assessments are finalized, taxing bodies (e.g., municipalities, school districts, park districts) determine their budgets and levy property taxes. The total tax levy is divided by the total assessed value of all properties to determine the tax rate.

Tax Bill Calculation

Property taxes are calculated by multiplying the assessed value of the property (after applying exemptions, if any) by the tax rate. The tax bill is then issued to the property owner, typically in two installments.

Key Points to Remember

  • Assessment Cycle: Properties are reassessed every three years in a rotating schedule for Chicago, North Suburbs, and South Suburbs.
  • Appeals Process: Property owners can appeal their assessment if they believe it is incorrect.
  • Impact on Taxes: A change in assessed value does not necessarily mean a proportional change in property taxes due to various factors, including changes in tax rates and equalization factors.

How to Appeal Your Property Tax Assessment in Cook County

Step 1: Review Your Assessment Notice

  • Reassessment Notification: Take time to carefully review your reassessment notice and compare the new assessed value with your previous assessment.
  • Verify Accuracy: Double-check that all details about your property (such as size, type, and condition) are accurate.

Step 2: Gather Supporting Evidence

  • Similar Properties: Gather information on properties similar to yours in the surrounding area that have lower assessments. These are commonly referred to as “comps” (comparables).
  • Recent Transactions: Search for recent sales of properties comparable to yours in your community.
  • Property Condition: Note any potential problems with your property that could impact its worth, such as structural issues, necessary repairs, or other conditions.

Step 3: File an Appeal with the Cook County Assessor’s Office

  • Online Filing: Appeals can be filed online through the Cook County Assessor’s Office website. You need to create an account if you don’t already have one.
  • Forms and Documentation: Complete the appeal form and attach all supporting documentation. This includes your comparables, recent sales data, and any photos or reports on property condition.
  • Deadlines: Be mindful of the filing deadlines. Each township has specific appeal periods, so check the Assessor’s Office website for the exact dates.

Step 4: Attend a Hearing (If Required)

  • Assessor’s Office Review: In some cases, the Assessor’s Office may adjust your assessment based on your submitted evidence without a hearing.
  • Formal Hearing: If a formal hearing is required, you will be notified of the date and time. Prepare to present your case, including all supporting evidence, in person or virtually.

Step 5: Appeal to the Cook County Board of Review (If Necessary)

  • Board of Review: If you are not satisfied with the decision from the Assessor’s Office, you can appeal to the Cook County Board of Review. This process is similar to the initial appeal, requiring submission of forms and evidence. Check their website for specific instructions and deadlines.

Step 6: Further Appeals (Optional)

  • Property Tax Appeal Board (PTAB): If you disagree with the Board of Review’s decision, you can appeal to the Illinois Property Tax Appeal Board. This is a more formal and lengthy process.
  • Circuit Court: As a last resort, you can file a lawsuit in the Circuit Court of Cook County.

Tips for a Successful Appeal

  • Be Thorough: Provide as much relevant evidence as possible to support your claim that your property is over-assessed.
  • Meet Deadlines: Strict adherence to deadlines is crucial. Missing a deadline can forfeit your right to appeal.
  • Professional Help: Consider hiring a property tax attorney or a consultant, especially if your case is complex or involves significant amounts of money.
  • Persistence: Be prepared for a potentially lengthy process. Multiple levels of appeal may be necessary to achieve a satisfactory outcome.

When to Consider Using an Attorney

Complex Cases

If your property is complex, such as a large commercial property, multi-unit residential building, or has unique features that make valuation difficult, an attorney can provide expertise in navigating the nuances of property tax law.

High Property Value

For high-value properties, the potential tax savings can be substantial. An attorney can ensure that your case is presented effectively, maximizing the chances of a favorable outcome.

Limited Time or Expertise

If you lack the time or expertise to gather evidence, prepare documentation, and present your case, an attorney can handle these tasks on your behalf, ensuring that everything is done correctly and on time.

Previous Unsuccessful Appeals

If you have appealed before and were unsuccessful, an attorney might bring a new perspective and legal arguments that could be more effective.

Benefits of Using an Attorney

  • Expertise: Attorneys specializing in property tax appeals have in-depth knowledge of the laws, regulations, and procedures involved. They understand how to present evidence and arguments effectively.
  • Negotiation Skills: An attorney can negotiate with the Assessor’s Office or Board of Review on your behalf, potentially reaching a favorable settlement without a formal hearing.
  • Legal Representation: If your appeal progresses to higher levels, such as the Illinois Property Tax Appeal Board or Circuit Court, having an attorney can be crucial. They can represent you in these formal legal settings.
  • Stress Reduction: Handling an appeal can be time-consuming and stressful. An attorney can take on the burden, allowing you to focus on other priorities.

Costs of Hiring an Attorney

  • Fees: Attorneys typically charge a flat fee or a percentage of the tax savings if your appeal is successful. Make sure to understand the fee structure before hiring an attorney.
  • Cost-Benefit Analysis: Weigh the potential cost of hiring an attorney against the possible tax savings to determine if it is a financially sound decision.

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