Why a Chicago Homeowner's Tax Bill Depends on Someone Else's Appeal

Every Chicago closing statement has a line for property tax prorations. In Cook County, that line is usually an estimate. Illinois property taxes are paid in arrears, so the seller credits the buyer for the months the seller owned the home. When the county's bills come out late, both sides have to agree on a number without seeing the bill it is supposed to match.

The bills have come out late two years in a row. The tax year 2025 second installment arrived about two months behind schedule, with paper bills mailed in early September and payment due October 1, 2026. WTTW reported that the usual schedule is release in early July and a due date in early August, and that the previous year's second installment was four months late. That estimate matters more in Chicago than in most places, because a homeowner's bill can rise even when nothing about the house changed.

The proration is a negotiated guess

The first installment is simple. It equals 55% of the prior year's total bill and is typically due March 1. The second installment carries everything that moved during the year, including new assessments, tax rates and exemptions. When that second bill is late, the proration rests on the last real bill plus a cushion. Here is what local real estate attorneys describe as common:

• 100% of the prior bill. Braverman & Makhlouf calls this common in stable years, and suggests 105% or 110% in reassessment years.
• 105% to 110%. Chicagoland Property Law gives this as the typical scale-up under normal conditions.
• 115% to 120%. The same firm says buyers worried about large assessment jumps during reassessment cycles may ask for this, which leaves sellers giving up more at closing.

When the estimate comes in low, the buyer covers the shortfall once the real bill arrives. To guard against that, attorneys draft post-closing re-proration agreements, which recalculate the credit from the actual bill. The seller pays any underfunded difference and the buyer refunds any overage. Another option is an escrow holdback, where part of the seller's proceeds sits with the title company until the final bill is paid. Either way, the closing statement records a negotiated forecast, and both parties have to agree on it before signing.

Last year's bill is a weak guide in Chicago

The forecast is hard because a Chicago homeowner's share of the tax load is set partly by other people's appeals. The Cook County Assessor sets values first. The Cook County Board of Review then has final authority to change any assessment appealed to it before tax bills are calculated.

Here is how homes' share of Chicago's total assessed value moved through the 2024 reassessment, according to the Assessor's Office:

The Assessor's numbers would have cut homeowners' share. Then the Board of Review reduced Chicago commercial values by 17%, or $4.3 billion in assessed value, and reduced residential values by 1%, or $0.4 billion. Homes ended up carrying a larger share than before. The pattern repeats. After the 2021 Chicago reassessment, residential property made up 53% of citywide assessed value once appeals were final, largely because of $6.2 billion in commercial cuts.

Part of the gap comes from who files. WBEZ reported in March 2026 that across the 2021 to 2023 reassessment cycle, businesses appealed 64% of the time and homeowners appealed 27% of the time. Successful business appeals lowered businesses' collective bills by $3.3 billion, or 12.5%, while residential bills rose $1.9 billion, or 6.9%. When a buyer studies a home's tax history, they are also looking at the outcome of appeals on office towers, hotels and retail buildings they will never own.

What the 2025 bills did, block by block

Chicago was not reassessed for the bills that just came due, and the burden still shifted a little. The Cook County Treasurer's tax year 2025 bill analysis, published in August 2026, found that Chicago commercial and industrial values each dropped more than 2% while residential values dropped 0.7%. That moved a bit more of the burden onto homeowners.

For tax year 2025 bills, payable in 2026:

• Total Chicago property taxes rose about $196 million, or 2.2%. Homeowner taxes rose $120.9 million, or 2.7%, and business taxes rose nearly $75 million, or 1.8%.
• The median homeowner bill rose 3.2% to $4,597. The commercial median was $11,146 and the multifamily median was $22,322.
• Taxes went up on nearly 660,000 residential properties and down on fewer than 66,000.

That 3.2% came after a much bigger jump. On the bills paid in 2025, the Chicago median homeowner bill rose 16.7% to $4,457. The citywide median also hides a wide spread. In that earlier cycle, the Treasurer found that changes in median residential value across Chicago ranged from a 7.7% decrease to a 131.8% increase, depending on the area. A buyer comparing two Chicago homes with similar list prices can end up with very different tax trajectories.

The Treasurer names three drivers: levy increases by local schools, the city, park districts and other taxing bodies; how a property's assessment moved relative to every other property's; and whether the property sits inside a Tax Increment Financing district or a Special Service Area. Only some of those show up on a listing sheet.

Why 2027 makes the estimate harder

Chicago's scheduled reassessment years are 2024 and 2027. In 2026, the Assessor is reassessing the south and west suburbs, and city properties are revalued only for permits, division work or other special circumstances. Anyone buying in Chicago this fall or next spring will own the home through a full revaluation, followed by a new round of Board of Review appeals. Those are the same conditions under which Braverman & Makhlouf suggests a higher proration percentage.

The office running that revaluation may change hands. In the March 2026 Democratic primary for assessor, Lyons Township Assessor Pat Hynes defeated incumbent Fritz Kaegi. At his election-night victory party, WBEZ reported, Hynes said:

"We will make property taxes more accurate, more equitable and more transparent."

The same report said Hynes wants to make development in the city easier, which would widen the tax base, and to improve assessment data. Both are stated campaign goals.

City Hall adds its own uncertainty. The city's September forecast put the fiscal 2027 budget gap at $882.4 million. Block Club Chicago reported that a 29-member City Council coalition said it would oppose a 2027 property tax increase. The Chicago Sun-Times' October 7 budget preview described Mayor Brandon Johnson focusing on taxes aimed at corporations. The city levy is one of several on a Chicago bill, and the September forecast said Johnson would present a balanced budget recommendation this fall.

Four things to check before the contract is final

1. The proration percentage. Which figure the contract uses, and how it accounts for 2027 being a reassessment year.
2. Whether there is a re-proration clause or escrow holdback. Either one ties the final credit to the actual bill.
3. The exemptions on the seller's current bill. Chicagoland Property Law warns that an expired or unrenewed senior, senior freeze or homeowner exemption can make the previous bill look artificially low.
4. Whether the current installment is paid. The Cook County Treasurer lists October 1, 2026 as the due date for this installment, and a Treasurer's Office payment notice says unpaid balances after that date accrue interest at 0.75% a month.

This post is general information, not legal, tax or financial advice. Your real estate attorney should confirm the right terms for your transaction.

FAQ

Why did my Chicago tax bill go up when my assessment barely changed? Your share of the total depends on how your assessment compares with every other property's, and on what each taxing body levies. For bills paid in 2026, Chicago commercial values fell faster than residential values, which shifted part of the load onto homes.

Can homeowners appeal too? Yes. Owners can file with the Assessor's Office and with the Board of Review, and the Assessor's appeal calendar lists the filing windows by township.

When is Chicago reassessed next? The Assessor lists 2027 as Chicago's next scheduled reassessment year.

If you are selling in Chicago before the 2027 reassessment, your proration terms belong in the pricing conversation from the start. Maranda Real Estate Group can show you how recent tax bills on comparable homes affect your net proceeds. Start with a free home valuation.