Using Comparable Properties to Appeal Your Cook County Assessment

The most effective way to appeal your Cook County property taxes is by showing that similar homes in your area are assessed at lower values. These similar homes are called "comparable properties" or "comps" — and they're the foundation of nearly every successful appeal.

What Makes a Good Comp in Cook County?

A comparable property should be similar to yours in the ways the Assessor uses for valuation:

• Size: Within 20-30% of your home's square footage
• Age: Built within 10-15 years of your home
• Location: Same township, ideally the same neighborhood or block
• Features: Similar number of bedrooms, bathrooms, and overall condition

Comps within your neighborhood carry the most weight. With over 1.5 million residential properties in Cook County, there's no shortage of potential comparables.

The $/sqft Metric

The single most important number in a property tax appeal is value per square foot. If your property's Fair Market Value works out to $300/sqft but comparable homes in your neighborhood are valued at $250/sqft, that's strong evidence your assessment is too high.

To calculate: divide the Assessor's Fair Market Value by the building square footage. For example, a home valued at $400,000 with 1,600 sqft = $250/sqft.

Understanding Cook County's 10% Ratio

Cook County residential properties are assessed at 10% of Fair Market Value. When comparing properties, you can use either Fair Market Value or Assessed Value — just be consistent. A home with a $400,000 market value has a $40,000 assessed value. The $/sqft comparison works the same way regardless of which value you use.

Two Types of Evidence

Equity — Comparable Assessments

Show that similar properties in your area have lower Fair Market Values per square foot. This is the most common and effective approach in Cook County. The Assessor and Board of Review both recognize that similar properties should be valued similarly — if yours is an outlier, that's grounds for a reduction.

Market Value — Recent Sales

Show that recent sales of similar homes indicate your property is worth less than the Assessor's Fair Market Value estimate. Use sale dates, addresses, and prices from the last 1-2 years. This is especially effective when the market has softened.

How Cook County Value Finds Your Comps

Cook County Value automatically analyzes your property against all residential properties in the Assessor's data. Our algorithm scores each potential comp on square footage similarity, year built, neighborhood proximity, and features. Higher-scoring comps carry more weight in the analysis.

Building a Winning Case

• Use 3-5 strong comps rather than many weak ones — quality over quantity
• Highlight the median $/sqft of your comps vs. your own $/sqft
• Be consistent — compare Fair Market Values to Fair Market Values
• Include both equity and sales evidence when available — they reinforce each other
• File at both levels (Assessor and Board of Review) for the best chance of success
• Cook County Value generates both types of evidence with a match-scored comp list ready for your appeal