The Property Tax Process

The Assessor's Office determines the value of each property within the County. It operates on a three-year, or “triennial”, cycle. Approximately one-third of the County is reassessed each year (meaning each individual property faces assessment every three years, rather than annually). Property values are determined through a statistical model based on factors like sale prices for similar properties. This model approximates the fair market value for each property in the County. The Assessor's Office also hears an initial round of appeals, allowing people to contest their property value if they feel it was determined incorrectly.

After the Assessor's Office certifies property values, property owners have the opportunity to appeal the value once again at the Board of Review. The determination of the Board of Review is the final opportunity to change the value at the County level.

The Illinois Department of Revenue calculates an equalization factor to standardize how properties are assessed throughout the state. Illinois law mandates that property is assessed at 33.33%, or one-third, of its market value. In Cook County, commercial property is assessed at 25% of its value and residential property at 10%, so the equalizer is applied to ensure all property in the County is assessed at an average of 33.33%. This classification system is permitted under the Illinois Constitution adopted in 1970, which authorizes counties to assess different property classes at varying levels.

Once the equalization factor is applied, the Assessor’s Office applies exemptions to all properties which receive them. Each exemption has certain eligibility criteria that property owners must meet, and taxpayers must apply to receive them.

Local governments set their budget levies. In other words, they decide how much money they need to collect from their jurisdiction to operate and administer their programs. They submit these levies to the Cook County Clerk.

The County Clerk’s office, using the set of assessed property values and the local governments’ budget levies, calculates tax rates for each unique set of taxing districts in the County. These rates are multiplied by a property’s assessed value, reflecting both the equalization factor and any exemptions, to calculate the actual amount owed. 

Calculations from the Clerk are transmitted to the Cook County Treasurer. The Treasurer’s Office is responsible for printing, mailing, and collecting property tax bills, as well as distributing funds back to local governments.