If you bought a house in Winnetka between January and late summer of 2026, your closing statement was probably built on a tax bill that no longer existed in any practical sense. Cook County's tax year 2025 second-installment bills went out about two months late, so north suburban closings in that window prorated property taxes on the 2024 bill. That bill still reflected values from the 2022 reassessment. The bill that reflected Winnetka's 2025 reassessment was scheduled to be mailed by September 1, 2026, and came due October 1.
So the reassessment did not hit Winnetka owners mainly through a much larger annual bill. The annual bill rose modestly. The cost landed in a specific place: the gap between what a closing credit assumed and what the October installment actually asked for.
How a 36% assessment jump became an 8.5% bill
Winnetka posted one of the largest assessment increases in the county's north region. According to the Cook County Treasurer's tax year 2025 bill analysis, the median residential assessed value across Winnetka's 4,490 residential properties went from $103,802 in tax year 2024 to $141,000 in tax year 2025, a 35.84% increase. Only Kenilworth, at 39.21%, and Prospect Heights, at 35.87%, rose more. Across the north and northwest suburbs as a whole, values grew 20%.
Bills moved far less. An analysis by the law firm Braverman & Makhlouf compared each property's 2025 bill with its own 2024 bill. It found the typical Winnetka single-family bill rose $2,246, or 8.5%, and the typical Winnetka condominium bill rose $151, or 2.8%.
The mechanism is the levy. Each taxing body decides how much money it will collect. The Cook County Clerk then sets a rate that spreads that levy across all the property in the district. When values rise across the board, rates fall. By the firm's count, the average tax rate in Winnetka fell about 19% for tax year 2025, compared with about 13% across the north and northwest suburbs.
That makes a home's assessment change relative to its neighbors the number that decides its bill. The Clerk's office illustrated this with a north suburban home worth $250,000 in 2024, carrying a $6,004 bill at the region's average rate. If that home's assessment stayed flat, its 2025 bill would fall to $5,268. A 20% increase would bring it to $6,482. A 30% increase would bring it to $7,089.
Here is how Winnetka sits beside its New Trier neighbors and Glenview. All figures compare each property's tax year 2025 bill with its own 2024 bill.
| Town | Median assessed value change, 2024 to 2025 | Typical single-family bill change | Typical condo bill change | Homes with bills up 10% or more |
|---|---|---|---|---|
| Kenilworth | +39.21% | +$3,458, 12.1% | too few to report | 55% |
| Winnetka | +35.84% | +$2,246, 8.5% | +$151, 2.8% | 45% |
| Wilmette | +32.93% | +$1,134, 7.9% | +$85, 1.2% | 41% |
| Glencoe | +28.56% | +$1,718, 7.3% | +$513, 6.6% | 42% |
| Glenview | not in Treasurer's top-ten list | +$1,043, 8.4% | +$342, 6.2% | 43% |
The bill-change figures come from the firm's own calculations on Treasurer data, so they measure something different from the Treasurer's median-bill figures. They also cover only incorporated towns. The Chicago Sun-Times reported that the median bill in unincorporated New Trier Township rose 27.8%, or more than $7,800. That figure describes a different set of properties than the Village of Winnetka.
Why the October installment carried the whole change
The Cook County billing schedule explains why a modest annual increase felt sharp at closing. The first installment is 55% of the prior year's total bill. The second installment absorbs everything else, including the full year-over-year change.
Braverman & Makhlouf works through the arithmetic with a bill that rises from $10,000 to $11,500:
- The first installment is $5,500, which is 55% of last year's $10,000.
- An estimate built on last year's bill would put the second installment at $4,500.
- The actual second installment is $6,000.
- That is $1,500 above the estimate, or one-third more.
For a Winnetka single-family home whose bill rose by the town's typical $2,246, the same structure put all $2,246 into the installment due October 1, 2026. Illinois property taxes are paid in arrears, so a bill the buyer receives and pays can include months the seller owned the house. The seller's closing credit is an estimate of that share.
Where a 105% proration stopped covering it
The Multi-Board Residential Real Estate Contract 8.0, the standard form in the Chicago area, prorates general real estate taxes through closing using the "most recent ascertainable full year tax bill." The percentage applied to that bill is left blank for the parties to fill in. Under paragraph 12, the proration is final at closing unless the parties agree otherwise in writing.
Berardi Law Office describes 105% of the prior bill as usual in many transactions, while noting that the figure is negotiated. A 105% figure builds in room for a 5% increase. Winnetka's typical single-family increase for tax year 2025 was 8.5%, and 45% of the town's homes saw their bills rise 10% or more. In a normal year that buffer might hold. In a reassessment year, with bills arriving after the spring closing season, it often fell short.
According to Braverman & Makhlouf, a buyer whose credit was based on 100% of the 2024 bill generally has to absorb the difference. The firm's separate explainer on reassessment years lists the tools parties have used when a closing falls before the new bill. They include a higher percentage, an estimate built from newly published assessed values, a written reproration agreement, or an agreed escrow. Each of those has to be written into the contract before closing. Once the proration is final, the contract offers no default way to revisit it.
What the 2025 bill settles for contracts signed now
For a Winnetka contract written in October 2026, the tax year 2025 bill is now the most recent ascertainable full-year bill, and it reflects the new values. That makes this fall's prorations more reliable than spring's. Three variables still sit outside that bill:
- Levy growth. For tax year 2026, the state tax cap limits most districts' levy increases to 2.6%. Payments on voter-approved bonds fall outside the cap.
- Exemptions that stay with the seller. A seller's senior exemption or senior freeze does not carry over to the buyer. A bill reduced by those exemptions understates what a new owner would pay.
- Pending appeals. If the seller has an appeal pending, the contract determines who receives any refund and how a changed bill is handled.
The exemption point matters most for downsizers. A long-held Winnetka home carrying a senior freeze can show a tax bill well below what the next owner will see. A buyer comparing that figure with a neighboring listing is comparing two different tax situations. Our Winnetka neighborhood page and seller resources go further into how listings in town are prepared and presented.
Why the 2025 assessment carries into 2026 and 2027
The north suburbs will not be reassessed again until tax year 2028. Unless a property changes or wins an appeal, its 2025 assessment is the base for its 2026 and 2027 bills. As of October 1, 2026, the appeal windows for New Trier Township were closed at both the Cook County Assessor and the Board of Review. For a Winnetka listing that goes live this fall or next spring, the 2025 assessment is the figure buyers and their lenders will see.
Regional shifts will still move bills at the margin. The Assessor's office reported in August 2026 that residential property now makes up 68% of total assessed value across the 13 north and northwest suburban townships after Board of Review appeals, up from 66% before the reassessment began. That is the highest residential share since the office began tracking the metric in 2019. The shift was smaller than in 2022, because Board of Review appeals cut commercial values by 14% this cycle compared with 20% in 2022. Across the region, the Treasurer reported that residential taxes rose $359.5 million, or 9.9%, for tax year 2025, while the median homeowner bill rose 6.7% to $8,007.
Short answers to the questions this raises
Did Winnetka's tax rate go down? On average, yes. Braverman & Makhlouf put the drop at about 19% for tax year 2025, because levies were spread across a much larger assessed base. A rate cut paired with a 35.84% median assessment increase still produced higher bills for most homes.
Why did Winnetka condo bills barely move? The typical Winnetka condominium bill rose 2.8% for tax year 2025, compared with 8.5% for single-family homes. Across the wider region, condominium bills rose faster than house bills, so Winnetka and Wilmette run against the regional pattern.
Why were the bills late? Cook County attributed the roughly two-month delay to the effects of last year's overhaul of its property tax technology on processes and timelines.
Does any of this apply to Lake County towns like Highland Park or Lake Forest? No. This post covers Cook County's billing schedule and its 2025 north-suburbs reassessment, which apply to towns such as Winnetka, Wilmette, Glencoe, and Glenview.
The tax proration is one of the few lines on a closing statement that can come back months later, and in a reassessment year it carries more weight than usual. If you're weighing an offer or preparing a Winnetka listing, Lotzof Malk Residential can walk you through how the 2025 bill, the seller's exemptions, and the contract's proration terms fit together, so the conversation with your attorney starts from the right numbers. Start the Conversation.
This article is general information, not legal, tax or financial advice. Consult a qualified professional about your situation.
