How your property tax bill is calculated
In Cook County, property tax bills are not calculated using the fair market value of a parcel of real estate. The Cook County Assessor estimates the market value of a property for taxation purposes. Your property tax bill is calculated on the monies needed to fulfill budgetary obligations.
School districts, local municipalities, and the rest of the agencies listed on your second installment property tax bill determine their annual budgets a year ahead of time. Once the total amount of budget money needed is known the tax levy can be calculated.
The tax levy is the percentage rate for imposing taxes. This value is determined by the Cook County Clerk.
After the total amount of budget money needed is determined and the tax levy is calculated, the Illinois Department of Revenue must also calculate a State Multiplier value in order to equalize the Cook County tax burden to the remaining 101 counties in Illinois. Then each parcel of property in a taxing district is given their allotment of property tax liability to pay.
Understanding your property assessment

For purposes of taxation, property value is estimated by analyzing sales data of similar properties in a neighborhood. Other methods for determining value include the Cost Approach and the Income Approach.


Assessed value is the taxable portion of the estimated market value of a parcel of property. Residential property in Cook County is assessed at 10% of its estimated market value.


For example, a property with an estimated market value of $200,000 would have an assessed value of $20,000 (200,000 x 10%).

Assessed value can be broken down into two components - a land assessed value and a buiilding (or improvement) assessed value. The land value and building value combined yield a total assessed value.

The County Assessor mails out a Notice of Proposed Assessed Valuation to property owners when there is a change in assessment. Property assessments are reviewed by the County Assessor every three years in Cook County (2014 was a re-assessment year for property owners in Stickney Township; 2017 and 2020 will also be re-assessment years).

How to determine if your residential property assessment is uniform

The Illinois Property Tax Code allows for all like property to be assessed equally, or uniformly.


One way to determine if your property assessment is uniform is by the price per square foot of the building. You can find this number by dividing the square footage of your building into the building value of your property assessment. (Condominiums are valuated using different criteria)


Consider the following example - a home with a living area of 1,200 square feet; a land assessed value of 5,000; a building assessed value of 20,000; and a total assessed value of 25,000.


We then have:

                        20,000 / 1,200 = 16.67 per square foot

Now we need to identify comparable properties. Comparable properties must have a lower total assessed value; they must be within your neighborhood; they must be the same classification; and they should be similar in style and structure to the subject property. Use the Cook County Assessor's website to identify comparable properties.


Comparable properties that meet the above listed criteria and have a lower building price per square foot are the supporting evidence one needs to substantiate the claim that their property assessment lacks uniformity.