If you are closing on a Chicago home between now and the end of the year, the number on your Closing Disclosure marked "property tax proration" is doing more work than usual. It always has to estimate a bill that does not exist yet. This year, that estimate is built on an older, shakier foundation than normal, because Cook County's second installment tax bill is late again, and the standard math both sides rely on to split the difference was not built for a delay this size.
That is the part worth sitting with before you sign anything. The delay itself is a county administrative problem. What it does to your proration credit is a transaction problem, and it lands on whichever party guessed wrong.
Why the Bill Is Late, and Why This Time Is Different
Cook County property tax bills go out in two installments. The first is simple: it is fixed by law at 55 percent of the prior year's total bill, mailed early in the year. The second installment is the one that actually reflects current assessments, current levies, and any exemptions on file, and it typically mails by early July with payment due August 1.
On June 9, 2026, Cook County Board President Toni Preckwinkle confirmed that the second installment for tax year 2025 would run about two months behind schedule, with payment unlikely before October and no firm date set at the time of the announcement. To help schools, libraries, and other taxing bodies manage the resulting cash-flow gap, the county reopened its Property Tax Bridge Fund Program, offering up to $300 million in no-interest loans, with applications accepted from July 20 through August 24, 2026.
This is the third year in a row the second installment has missed its normal schedule. The prior cycle was worse: the tax year 2024 bill was not mailed until November 14, 2025, with payment due December 15, 2025, four months late instead of two. That delay was expensive in ways that reached beyond individual homeowners. Chicago Public Schools alone absorbed an extra $33 million in borrowing costs from the cash-flow gap created by the late bill, according to reporting on the delay's downstream effects. The county has tied the recurring slippage to an ongoing overhaul of its property tax technology system, one that officials acknowledge still has unresolved issues.
None of this changes how much tax anyone owes. It changes when the number becomes known, and in a closing that happens between the estimate and the actual bill, that timing gap is exactly where money gets misallocated.
Every Chicago Closing Is Already a Guess
Illinois taxes are paid in arrears, meaning the bill you pay this year covers last year's obligation. A seller who owned a Chicago home through June of this year has accrued a real tax liability for those months, but no bill exists yet to attach a number to it. The seller credits the buyer at closing for that estimated share, and the buyer later pays the actual bill once it arrives.
Because nobody has the real number at the closing table, Illinois contracts prorate against the most recent available bill and apply a percentage designed to approximate the increase. In the collar counties, DuPage and Lake among them, that convention typically runs at 105 percent of the prior bill, reflecting more modest and more predictable year-over-year growth. In Chicago, the customary figure under the standard Multi-Board Residential Real Estate Contract runs higher, at 110 percent, because Cook County assessments and levies have historically climbed faster and less predictably than in the surrounding suburbs.
That 110 percent convention was built to absorb a normal amount of uncertainty. What it was not built for is a bill that arrives on a schedule nobody can pin down three years running, based on an assessed value from a reassessment cycle where one third of the county's townships get revalued each year. The second installment takes longer to calculate precisely because it has to reflect that year's actual assessment and rate changes, which is also why it is the installment that keeps slipping. Every additional month of delay stretches the gap between the number a proration is estimating and the number that eventually shows up, and a 110 percent guess against an older baseline carries more risk in either direction than it did in a year when the bill arrived on time.
What This Looks Like on a Fall Closing
Picture a closing in September, with the seller crediting the buyer using 110 percent of the prior year's bill because that is still the most recent figure available. If the bill that eventually arrives in October runs meaningfully higher than that estimate, the buyer absorbs the shortfall unless the parties agreed in advance to revisit the number. If it runs lower, the buyer keeps the difference and the seller has no path back to it. Both outcomes are allowed under a standard proration. Neither is what either side actually intended.
A re-proration agreement, entered into after the real bill is issued, is the mechanism Illinois closings use to true up that gap. It is a standard tool, not an unusual request, and it is worth confirming in writing before closing rather than negotiating after the fact once the numbers no longer match anyone's expectations.
There is a second, more mechanical squeeze building for anyone who pays taxes directly rather than through mortgage escrow. The first installment for tax year 2025 was itself delayed a month this year, pushed to an April 1 due date instead of the usual March 1. If the second installment lands in October as projected and the next first installment returns to something closer to its normal early-year schedule, two sizable payments could land closer together than usual instead of spread comfortably across the year. That is a cash-flow planning question worth raising with a lender or accountant now, not in October when the bill actually shows up.
| Normal schedule | Tax year 2024 bill | Tax year 2025 bill | |
|---|---|---|---|
| Mailed | Early July | November 14, 2025 | Projected September 2026 |
| Due | August 1 | December 15, 2025 | At least October 2026 |
| Delay | None | About 4 months | About 2 months |
None of this is unique to a small slice of the market. Closed sales activity across the Chicago area is projected to grow another 5.1 percent in 2026 compared with 2025, according to a forecast built by DePaul University's Institute for Housing Studies for Illinois REALTORS. A meaningful number of buyers and sellers are walking into this exact timing gap this fall, whether they know it or not.
The Exemption That Does Not Follow the House
There is a second detail worth confirming before closing, separate from the delay itself but related to it. The Homeowner Exemption, which reduces a property's equalized assessed value by $10,000, is tied to whoever owned and occupied the home as of January 1 of the tax year, not to the property itself. It does not transfer to a new owner at closing. A buyer who assumed the tax figure they saw while shopping already reflected their own future exemption can find the real bill runs higher once it arrives, because the seller's exemption comes off and the new owner has not yet filed under their own name.
The fix is straightforward. New owners apply for the Homeowner Exemption directly with the Cook County Assessor's Office after closing, and once approved it renews automatically in future years as long as ownership and occupancy stay the same. The point is not to skip the step, but to know it exists before the first real bill lands and the gap between expectation and reality becomes a conversation instead of a surprise.
A Few Questions Worth Asking Before You Sign
Does the delay change how much tax I ultimately owe? No. It changes when the bill is calculated and issued, not the underlying tax obligation. The timing does affect which calendar year a payment counts toward for anyone tracking deductions.
If my mortgage is escrowed, do I need to do anything? Your lender pays the bill once it is issued and typically adjusts your monthly escrow contribution afterward to account for the actual amount. It is still worth asking your lender how they plan to handle a bill that lands later than usual, so an escrow shortage does not surprise you next year.
Is this a Chicago-specific issue or does it affect the whole county? The delay is county-wide, since the Cook County Treasurer's Office issues and processes bills for the entire county. This piece focuses on Chicago closings because that is where the 110 percent proration convention and the exemption transfer question come up most often in day-to-day transactions.
A late tax bill is an inconvenience for most homeowners. At a closing table, it is a number two parties are trusting each other to estimate correctly, based on assumptions that were more reliable in a year when the county's own timeline held. If you are buying or selling in Chicago this fall, it is worth a direct conversation with your attorney about how your contract handles a proration gap before you get to the closing table, not after.
If you want to talk through how this affects a specific purchase or listing, from the proration language in your contract to what an accurate escrow cushion looks like given this year's timeline, Nina Trivedi brings 25 years of accounting and tax background to exactly these kinds of questions. Start the Conversation before you sign.
