When an Orland Park sale closes this December, the seller's tax credit to the buyer is calculated from the most recent full-year bill already issued. In Orland Township right now, that bill was calculated on values that came out of the 2023 reassessment, and the 2026 reassessment just replaced them.
The Cook County Assessor mailed Orland Township's reassessment notices on September 24, 2026. Across 37,567 residential parcels, the median assessment rose 19.9% from each home's final 2025 value, and 98.8% of homes went up, according to an analysis of county assessment files by Cook County Tax Appeal published September 29, 2026. None of that shows up yet on the bill your closing credit will be calculated from.
The Bill on the Closing Table Predates the New Values
Cook County property taxes are paid in arrears. When a home sells, the seller credits the buyer for the stretch of time they owned it before any bill for that period arrived. The Multi-Board Residential Real Estate Contract 8.0, the standard form for most Chicago-area residential deals, handles this in paragraph 12. It prorates general taxes through the closing date against a blank "% of the most recent ascertainable full year tax bill." The form doesn't fill in a default number. It also makes that proration final at closing unless the parties sign a written agreement saying otherwise.
Here is how Orland Township's calendar lines up against that clause:
| Item | Timing | What it reflects |
|---|---|---|
| Tax Year 2025 second installment | Due October 1, 2026 | Values from the 2023 reassessment cycle |
| 2026 reassessment notices | Mailed September 24, 2026 | New 2026 values |
| Assessor appeal deadline | November 6, 2026 | Last day to contest the 2026 notice at the Assessor |
| Tax Year 2026 first installment | Customarily around March 1, 2027; not yet published | Exactly 55% of the Tax Year 2025 total |
| Tax Year 2026 second installment | 2027 | The first bill to use the 2026 reassessed value |
The Assessor's own explainer says the first installment is a fixed 55% of the prior year's total. The new assessment only flows into the second installment the following year. The Cook County Treasurer hasn't posted Tax Year 2026 due dates yet, so the March date is the usual timing, not a confirmed deadline.
Put those pieces together. A sale that closes between now and the summer of 2027 will usually prorate against the Tax Year 2025 bill, because it's the latest full-year bill on record. And a December closing credits the buyer for nearly all of 2026, which is the very year that was reassessed.
What a 19.9% Assessment Increase Does to a Bill
A 20% higher assessment doesn't mean a 20% higher tax bill. When the total assessed value of a taxing district grows, the rate is recalculated by dividing each district's levy over that larger base. The Assessor's Orland Township page says an individual bill can't be predicted from one property's assessment change, because each property's tax depends on its share of total assessed value in each taxing district.
That makes a home's increase relative to everything else in the district the number that matters. The Cook County Tax Appeal analysis reports these median changes from 2025 to the 2026 notices:
- Residential parcels: +19.9%, with total residential assessed value up 20.8%
- Class 3 large apartment properties: +18.6% across 94 parcels
- Class 5 commercial and industrial properties: +15.6% across 950 parcels
These are the firm's figures, drawn from county files. They aren't a summary percentage the Assessor published. If gaps like these survive the appeal season, homes would carry a somewhat larger share of the same levies than they did under the 2023 values. That would push residential bills up even after rates come down. Appeals at the Assessor and the Board of Review will move those medians before any 2027 bill is calculated, so treat this as a direction, not a forecast.
The Assessor's estimates are close to recent sales. For single-family homes across the township, the 2026 Assessor estimate is $408,000, against a 2025 median sale price of $405,000. In other words, the new values roughly match what homes have actually sold for. The old ones, in place since the 2023 cycle, didn't. The bill most closings will prorate against carries that older, lower base.
Running the Arithmetic on a December Closing
The proration math is simple. Lauren Jackson Law lays it out as the prior bill, times the negotiated percentage, divided by 365, times the number of days the seller owned the home.
Here is a hypothetical. Say a home's Tax Year 2025 bill totaled $9,000 and the sale closes December 15, 2026. The seller owned the home for 349 days of 2026.
- At 100%, the credit is about $8,605.
- At 110%, the credit is about $9,466.
The 10-point difference in the percentage is worth about $860 in this example. That's the money moving between buyer and seller at the table, and the clause makes it final unless the parties agree otherwise in writing.
Now compare that with a median Orland Township home under the new values. In the firm's illustration, a home assessed at $38,000, or about $380,000 of market value, is multiplied by the 3.03 state equalizer to reach $115,140 of equalized value. At the township's median 2025 composite rate of 8.98% of equalized value, that comes to about $10,340 of gross tax. After roughly $900 for the Homeowner Exemption, it's around $9,440. Those figures combine a 2026 assessment with a 2025 rate, and the firm notes that the rate will be recalculated on the larger base. So the example is an upper reference point, not a prediction of anyone's 2027 bill. Composite rates in the township also range from 7.8% to 10.8% depending on tax code, which is why two Orland Park homes at the same price can carry noticeably different bills.
How Attorneys Handle the Gap
Since the contract leaves the percentage blank, it gets negotiated in every deal, and attorneys describe the usual range differently. Braverman & Makhlouf says 100% is common in stable assessment years, with 105% or 110% used as a buffer when increases are expected. Lauren Jackson Law says most contracts land between 105% and 110%. A September 2026 post from Chicagoland Property Law says buyers worried about large reassessment jumps may push for 115% to 120%, "forcing sellers to leave significantly more money on the table at closing."
A higher percentage is a guess made at closing. Chicagoland Property Law describes two ways to settle the number later:
- A post-closing re-proration agreement. Buyer and seller agree to recalculate once the actual bill comes out. The seller pays any shortfall, or the buyer refunds any overpayment.
- A title escrow holdback. Part of the seller's proceeds stays with the title company until the final bill is calculated and paid.
Braverman & Makhlouf also lists estimating the credit from newly published assessment data as another option for a reassessment year. The same Chicagoland Property Law post notes that these arrangements add legal friction, cost, and paperwork after the closing date. For an Orland Park sale this winter, a re-proration could stay open until the Tax Year 2026 second installment is issued sometime in 2027.
The Appeal Window Overlaps the Contract Period
Appeal deadlines matter for the same deals. The Assessor's window for Orland Township closes November 6, 2026. The Orland Township Assessor's office offers help with appeals but asks residents to submit its request form or visit by November 4, 2026. It also warns that it may stop taking requests earlier if it reaches capacity. When the Board of Review portal was checked, it listed Orland under pre-file townships, with no opening or closing date posted yet.
Last cycle shows why that second window matters. For Tax Year 2025 residential appeals in Orland Township, the Assessor reduced 350 of 3,700 appeals, or 9.5%, with an average cut of 7.1% for those that won. The Board of Review reduced 2,367 of 6,353, or 37.3%, with an average cut of 6.5%. Any appeal of the reassessment shows up on the second-installment bill the following year.
For a home under contract right now, that creates a timing problem. The seller still owns the property and is the one positioned to appeal before November 6, but the buyer will pay most of the 2027 bill that any reduction affects. With a re-proration agreement in place, a lower 2026 assessment also lowers the actual bill the seller's share is reconciled against. That gives both sides a reason to coordinate on the appeal before the deadlines pass rather than after closing.
This post is general information, not legal, tax, or financial advice. Confirm the proration terms and appeal options for your own transaction with your real estate attorney and a qualified tax professional.
If you're buying or selling in Orland Park this winter, the tax line in your contract deserves as much negotiation as the price. My team at Amanda Stapleton will run the proration numbers for your exact closing date, map them against the 2026 reassessment, and coordinate with your attorney before the November 6 appeal deadline. Book a Market Strategy Call.
