A buyer sits down at a title company on Elston or Lincoln Avenue this month, scans the closing statement, and stops on one line: a tax credit from the seller worth several thousand dollars more than the number they'd mentally budgeted. It isn't a mistake. It isn't a negotiating tactic gone sideways. It's Cook County's arrears system doing what it always does, except this fall it's doing it while the county's own tax bills are running behind schedule for the second year running.
If you're closing on a home anywhere in Chicago this September or October, that line item deserves more attention than most people give it. Here's the mechanism behind it, why the timing this year makes it worth double-checking, and what to do if the numbers on your statement don't match the bill that eventually lands.
Why There's a Tax Credit on Every Chicago Closing Statement
Cook County collects property taxes a year behind. The bill you pay in 2026 covers 2025. That single fact is the reason every Chicago purchase contract includes a tax proration, because at the moment of closing, nobody has a final bill for the months the seller actually owned the home during the current tax year.
The county splits payment into two installments. The first is simple: 55 percent of the prior year's total bill, due early in the year as a placeholder. The second installment is the real number. It reflects the actual assessed value, the current tax rate, and whatever exemptions applied, and it's typically not calculated and mailed until well into the second half of the year.
Because that second installment doesn't exist yet at most closings, buyer and seller agree to a proration instead. The seller credits the buyer for their share of an estimated bill, calculated for the number of days they owned the property that year. The buyer then owes the full year's tax bill once it eventually comes due, but they've already been compensated for the seller's portion.
The Percentage Nobody Explains Until Someone Asks
Here's the part that catches people off guard even in a normal year. The credit isn't simply the prior year's tax bill divided by 365 and multiplied by however many days the seller owned the home. It's that number multiplied by a percentage, and that percentage is negotiated.
Most Chicago-area contracts use somewhere between 105 and 110 percent of the last known full year's tax bill, not 100 percent. The reason is straightforward: property taxes in Cook County almost always go up year over year, so the extra cushion protects the buyer from being under-credited for taxes that will be higher by the time the real bill arrives. In a year with a fresh reassessment or an unusually large expected increase, some buyers negotiate for 115 or even 120 percent instead.
That percentage isn't written into state law. It's a term in the purchase contract, and it's often left open until the attorney review period under the standard Illinois Multi-Board Residential Real Estate Contract, which means it's genuinely up for discussion between the parties rather than a fixed formula either side can assume.
To see why the number matters, take an illustrative example. Say a north-side single-family home carried roughly $9,000 in annual property taxes on its last known bill. At a 100 percent proration, a seller who owned the home for the first 240 days of the year would credit the buyer about $5,918. At 110 percent, that credit rises to roughly $6,510. On a single closing, that's nearly $600 in the buyer's favor, and if the actual tax bill turns out even higher than the prior year's number suggested, a 100 percent proration leaves the buyer covering the gap out of pocket months later.
The Number Nobody Had All Year
This is where 2026 gets genuinely unusual, and it's the reason this deserves more than a passing mention in the fine print.
Second installment tax bills in Cook County are typically issued in early July and due about a month later. That schedule broke down badly for tax year 2024, when a system overhaul tied to a new Tyler Technologies platform at the Cook County Treasurer's Office pushed the second installment bill out four months late, with a due date of December 15, 2025. This year, tax year 2025's second installment bills were mailed by September 1, 2026, with payment due October 1, 2026, roughly two months later than the typical schedule. Cook County officials described the repeated delay as a cascade effect from the same system transition.
| Tax Year | Second Installment Due Date | Compared to Typical Schedule |
|---|---|---|
| 2023 | August 1, 2024 | On typical schedule |
| 2024 | December 15, 2025 | About four months late |
| 2025 | October 1, 2026 | About two months late |
Here's why that timeline matters more than a footnote about bureaucratic delays. Every closing that happened in Chicago between roughly January and August of this year was negotiating a tax proration without access to a current, finalized second installment bill for the most recent tax year. Sellers and buyers were working off whatever the last available full bill said, sometimes a year or more out of date, and applying the standard 105 to 110 percent cushion to a number that may or may not have reflected how much rates and assessments had actually moved.
Add in the fact that 2024 was Chicago's citywide triennial reassessment year, which reset assessed values across the city before that same bill got delayed four months, and you have a stretch of many months where the base number used for closings across Lincoln Park, Lakeview, North Center, and every other Chicago neighborhood was built on incomplete information by design, not by anyone's error.
Now that the real tax year 2025 bill has finally landed, anyone who closed earlier this year on an estimate is finding out for the first time whether their proration cushion was actually big enough.
The Error That's Cheap to Catch and Expensive to Miss
The most common mistake on a Chicago closing disclosure is using 100 percent of the prior year's bill instead of the standard 105 to 110 percent. Caught at the closing table, it costs nothing to correct. The title company simply adjusts the figure before anyone signs.
Caught after closing, it's a different conversation. Fixing it requires a re-proration agreement between the parties, and if the seller isn't cooperative, it can end up in small claims court over a few hundred or a few thousand dollars that could have been resolved with one extra look at the settlement statement.
If you have a mortgage escrow account, it's worth knowing that doesn't replace this credit either. Escrow covers your own future tax payments going forward. The proration is a separate, one-time settling of accounts between the two parties at the moment of sale.
A Note for Buyers Comparing Chicago to the Suburbs
The arrears system and the proration mechanics apply the same way whether you're buying in the city or in Cook County suburbs like Evanston or Oak Park, but the underlying tax burden doesn't. Chicago's effective property tax rate runs roughly 1.8 to 2.0 percent of market value, while towns like Oak Park and Berwyn commonly run 2.5 to 3.5 percent or higher. Worth noting for suburban buyers specifically: 2025 was the reassessment year for Cook County's northern suburbs, which means Evanston homeowners are seeing their first post-reassessment bill land in this same delayed cycle, on the same October 1, 2026 deadline. If you're weighing a north-side Chicago listing against a comparable home in an inner-ring suburb, the tax line on your eventual closing statement is worth pricing in specifically, not estimating from a citywide average.
A Few Questions Worth Asking Before You Sign
If I already closed this year, can I go back and fix the proration? Only if your contract allows for a post-closing re-proration once the actual bill is available, and only within whatever timeframe that agreement specifies. It's worth pulling your closing statement and checking the language now, before the window closes.
Is the percentage negotiable if I'm the buyer, not the seller? Yes. It's a contract term like any other, and it's common to raise it during attorney review, especially if the seller had an exemption, like a senior exemption, that won't carry over to you as the new owner and could mean the next bill jumps more than the standard cushion accounts for.
Does a higher proration percentage mean I'm overpaying? No. A higher percentage protects you as the buyer by building in a bigger credit against taxes that are expected to rise. The risk runs the other direction: a proration set too low leaves you short when the real bill arrives.
If you're weighing a purchase or a sale on the north side this fall and want to walk through what your specific numbers should look like before you're staring at them across a closing table, Clare Sells Homes offers a Free Home Valuation & Staging Consult where we can talk through timing, pricing, and exactly what belongs on your settlement statement before you ever sign a contract.
