The Illinois Property Tax Number You Have Read Is a Homeowner's Number

Key takeaways

Illinois publishes tax rates against equalized assessed value, not market value. The Department of Revenue's 2024 average residential rate is 7.94 statewide and 8.25 in Cook County, per its own Table 8.
Outside Cook, property is valued at 33 1/3% of fair cash value under 35 ILCS 200/9-145, so 7.94 against a third of market works out near 2.6% of market value before any exemption.
Cook assesses residential classes at 10% and then the state equalizer lifts it, tentatively 2.8683 for 2025, so 8.25 against roughly 28.7% of market works out near 2.4% of market value before any exemption.
The general homestead exemption requires the owner to occupy the property as a principal residence under 35 ILCS 200/15-175. An investor receives none of it, which is why the tax line inside PITIA sits above the published homeowner median.

Program and regulatory figures verified September 15, 2026. Details change; confirm your scenario with us.

By Mike Certo, Cornerstone First Mortgage · NMLS #260555 · Updated September 15, 2026

Every article about Illinois property tax quotes an effective rate around two percent. That figure describes a house somebody lives in, with the exemptions that come with living in it. Your rental carries none of them, and the difference lands in the denominator of your DSCR.

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Illinois rates are not what you think they are measured against

An Illinois tax rate is quoted against equalized assessed value, not against what you paid. That single fact produces most of the confusion. The Department of Revenue publishes the rates in its annual Property Tax Statistics, and the 2024 averages are these.

Area	Average total rate	Average residential rate
Statewide	7.89	7.94
Cook County	8.13	8.25
Collar counties	7.64	7.60
Rest of state	7.74	7.87

Illinois Department of Revenue, Property Tax Statistics, Table 8, Average Tax Rates, 2020 to 2024. These are rates on equalized assessed value.

Converting to something you can underwrite with

To turn that into a share of market value you need the assessment level, and Illinois has two of them. Outside Cook, 35 ILCS 200/9-145 values property at 33 1/3% of fair cash value. In Cook, residential classes are assessed at 10% and the Department of Revenue then applies an equalization factor, tentatively 2.8683 for 2025. The arithmetic is worth seeing rather than taking on trust.

Where	Assessed share of market	Rate	Roughly, as a share of market value
Outside Cook	33 1/3%	7.94	about 2.6%
Cook County	10% lifted by 2.8683, about 28.7%	8.25	about 2.4%

Derived, not published: we are multiplying the Department's rate by the assessment level. Both results are before exemptions, and the equalization factor is tentative and annual.

The part that applies to you and not to the article you read

The general homestead exemption reduces equalized assessed value, and 35 ILCS 200/15-175 conditions it on the owner occupying the property as a principal residence. That is the whole mechanism behind the friendly effective rates in circulation. You do not get it on a rental. So when a calculator pre-fills an Illinois tax line from a published median, it is pre-filling a number that belongs to an owner-occupant, and your DSCR comes out better on the screen than it will in underwriting.

Cook adds one more thing worth knowing if you are converting a home you used to live in. In counties of three million or more, where the assessor issues a notice of discovery and the property is no longer occupied by its owner as a principal residence on January 1, the owner has to say so on the assessor's form, received by March 1 of the collection year. Miss it and the exemption comes off anyway.

Where Cook genuinely helps, and where it does not

Cook is the only Illinois county that classifies, and the classification is real money on larger buildings. Residential classes sit at 10% and commercial and industrial at 25%, and Major Class 3 Multi-Family sits inside the residential section, apartment buildings of seven or more units included. A building that would be pushed into a commercial class elsewhere stays residential in Cook. What Cook does not do is make your bill smaller than a downstate bill, because the equalizer exists precisely to pull every county toward the same standard. The class detail is here.

We run the real tax line when we underwrite rather than a median. See the programs, then let us check it against the actual bill.

Mike Certo · NMLS #260555 · Cornerstone First Mortgage NMLS #173855 · Equal Housing Lender. Educational content, not a loan commitment and not legal or tax advice. Assessment levels, the state equalization factor, county tax rates and city rental ordinances change, and the figures here carry the date we verified them. Confirm current requirements with the county assessor, the county clerk, your CPA, or an Illinois real estate attorney before you buy. Loans are subject to buyer and property qualification.