Illinois Property Tax Calculator (2026)

Illinois property tax calculator: the formula

Illinois homes are assessed at one-third of market value, except in Cook County, where residential property is assessed at 10%. The Department of Revenue then applies an equalization factor so that, on average, Cook assessments match the statewide one-third level. The result is the equalized assessed value (EAV). Exemptions come off EAV, and the remainder is taxed at the composite rate of every district on your tax code.

Example: a $350,000 Chicago home has an assessed value of $35,000. Multiplied by the 3.03 factor, the EAV is $106,050. After the $10,000 homeowner exemption, $96,050 is taxed at 6.853%, giving $6,582 a year.

Cook County equalizer

The final 2025 factor for Cook County is 3.03, almost unchanged from 3.0355 for 2024. The factor does not raise total taxes: districts levy a fixed dollar amount, and the rate adjusts to the tax base. It shifts the share paid by Cook County compared with other counties for state-wide limits and moves the value of the fixed-dollar exemptions.

Homestead and senior exemptions

The general homestead (homeowner) exemption reduces EAV by $10,000 in Cook County, $8,000 in the collar counties next to Cook and $6,000 elsewhere. Owners 65 or older get a further $8,000 in Cook and the collar counties and $5,000 elsewhere. The Senior Freeze holds EAV at its base-year level for seniors with household income of $65,000 or less and must be filed every year.

In the Chicago example the senior exemption cuts the bill from $6,582 to $6,034. Other exemptions cover people with disabilities, veterans with disabilities and new improvements (up to $75,000 of added value for four years).

Chicago and suburban tax rates

Chicago's general composite rate rose to 6.853% for tax year 2025 from 6.619%, mostly because of a higher Board of Education levy. Suburban rates are often higher because less commercial property shares the load. In DuPage, Lake and Will counties median bills are larger than in Cook even though homes are similar in value. Find your composite rate on your bill or the County Clerk's tax code rate summary.

Same home, different Illinois counties

The assessment level and exemptions change the result even before rates differ. The table applies one 7% composite rate to a $350,000 home in each county type, so only the assessment rules vary. Real suburban and downstate rates are often higher or lower than this, so use the rate on your own bill.

How to lower an Illinois property tax bill

Check that every exemption you qualify for appears on the bill; missed exemptions in Cook County can be claimed for earlier years through a certificate of error. If the market value looks too high, compare it with recent sales of similar homes. In Cook County you can appeal first to the Assessor when your township is reassessed, then to the Board of Review, and finally to the state Property Tax Appeal Board. Elsewhere, appeals go to the county board of review. A lower assessment reduces only your share; the districts still collect their levy.

Property tax in DuPage, Lake, Will and Kane counties

The collar counties around Chicago have some of the highest bills in the state. Homes there are assessed at one-third of market value with an equalization factor near 1, and both the general homestead and senior exemptions are $8,000 of EAV. Census figures for owner-occupied homes show how the median bill compares with Cook County:

Illinois income tax credit for property tax

Homeowners can claim a credit of 5% of the property tax paid on their Illinois principal residence on Form IL-1040, Schedule ICR. It is not available if federal adjusted gross income exceeds $500,000 on a joint return or $250,000 on other returns. The credit is nonrefundable: it can cut your Illinois income tax to zero but not below. In the Chicago example the $6,582 bill is worth a credit of up to $329. Rental property, second homes and vacant land do not qualify.

When Cook County bills arrive

Illinois taxes are paid a year behind. The first installment, due in spring, is 55% of the prior year's total. The second installment, usually mailed in summer or autumn, reflects the new assessment, exemptions and rates. In 2026 the second installment of the 2025 tax year was due October 1.