Tinley Park's 2026 Cook Reassessment Reaches Across the County Line

Cook County's 2026 reassessment reaches Tinley Park homes on the Will County side too, according to the village's own tax FAQ. Each spring the Will County side gets its tax bill before anyone knows Tinley Park's final Cook County value. Will County fills that gap with an estimate and settles the difference on the next year's bill.

This fall that has a deadline attached. Orland Township homeowners got Cook County reassessment notices on September 24, 2026, and the Assessor's appeal deadline is Friday, November 6, 2026, according to the Cook County Assessor's Orland Township valuation page. If you're buying in Tinley Park right now, on either side of the line, that date belongs on your calendar. You don't need it to file anything. You need it because the value being finalized now feeds the bills that come later.

Two Clocks Inside One Village Boundary

Tinley Park covers parts of four assessment townships. Bremen, Orland and Rich are in Cook County, and Frankfort is in Will County. The two counties set values on different schedules, and in 2026 those schedules don't line up.

On the Cook side, the Cook County Assessor's calendar confirms the south and west suburbs are in their reassessment year. Bremen Township notices went out August 12, 2026, and that appeal window with the Assessor closed September 24. Orland's window is the one still open. Both township pages say the estimated fair market value on the notice will show up on tax bills in 2027.

On the Will side, the Will County Supervisor of Assessments lists a 2026 equalization factor of 1.0415 for Frankfort Township, applied to residential property only. The county explains that these factors come from a three-year sales-ratio study of 2023, 2024 and 2025 transactions for the 2026, payable 2027, tax year. Put simply, the posted factor lifts residential assessments in Frankfort Township by about 4.15 percent. Will County last ran a quadrennial reassessment in 2023, according to Tinley Park's 2024 annual financial report, so the next countywide general reassessment would likely come in 2027.

The Look-Back That Ties the Two Sides Together

The Village of Tinley Park and the Tinley Park Public Library each levy one dollar amount across the whole village. That levy gets split between the counties based on how much property value sits in each. The catch is timing. Will County prepares its bills in April, and Cook County's value for that same tax year isn't final yet. The village's Will County Property Tax FAQs lays out what happens next:

"The difference between the estimated share previously billed, and the actual share (that should have been billed, if the actual EAV had been available), is added to the following year's estimated share of the levy, factored into the Will County tax rate, and ultimately billed to taxpayers in the Will County portion of Tinley Park."

The same FAQ says this look-back "will skew the comparison of tax rates and the amount of taxes computed for the Village of Tinley Park between two tax years." Tinley Park isn't unusual here. The FAQ cites the Will County Tax Extension Office as reporting about 90 taxing districts that reach into other counties.

Here's how it runs, step by step:

1. The Village Board adopts its levy. For 2025, the board adopted a levy of $32,225,279 on December 16, 2025, including $6,035,031 for the Public Library, according to the December 16, 2025 board packet.
2. In spring, the Will County Clerk's Tax Extension Office estimates Tinley Park's Cook County tax base and bills the Will side its share based on that estimate.
3. Later in the year, once Cook's actual value is known, Will County works out what the Will side should have paid.
4. The difference goes onto the following year's Will County rate, up or down.

Now drop a Cook County reassessment into step 3. If the reassessment moves Tinley Park's Cook value one way or the other, the Will side's share of a fixed levy shifts with it, and a buyer on that side sees the correction a year late. Cook's bills have also been running behind. Cook County announced on June 9, 2026 that the next bills would come about two months late, and WTTW reported that the 2025 second installment was due October 1, 2026.

Why Comparing Rates Across the Line Misleads

Most buyers comparing two Tinley Park homes put the tax rates side by side. The village's historical numbers show how far off that can lead you. For levy year 2023, the most recent year on the village's transparency portal, the Village's general corporate rate was $1.251 per $100 of equalized assessed value on Cook County property and $1.5954 on Will County property. The library fund rate was $0.309 on the Cook side and $0.3943 on the Will side.

Those rates fund the same village and the same library, yet they differ by county. Part of the reason is the look-back. Part of it is that each rate is charged against a tax base built a different way. The FAQ describes a rate as the levy divided by the tax base, so "when the tax base (EAV) decreases, the tax rate will increase; even if the tax levy does not change." The state also equalizes each county with its own multiplier. The Illinois Department of Revenue set Cook County's final 2025 factor at 3.0300 on June 16, 2026, and Will County's final 2025 factor at 1.0000 on February 9, 2026, according to the IDOR press release archive.

The village's tax-year 2023 sample bills show the same pattern for the whole bill:

• Orland Township, Cook County side: total rate of $9.205, with 68% to education, 14% to the Village, 11% to county and township, 4% to the park district and 3% to the library.
• Frankfort Township, Will County side: total rate of $10.1019, with 65% to education, 16% to the Village, 10% to county and township, 5% to the park district and 4% to the library.

On its own, a higher Will-side rate tells you little about which home costs more to own. The number that counts is the dollar amount on the actual bill for the actual parcel.

How Much the Cook Side Weighs

The look-back matters on the Will side because Cook holds most of the village's tax base. On the village's township chart for 2023, the three Cook townships total $1,576,390,198 in EAV: Bremen $415,139,859, Orland $1,024,951,660 and Rich $136,298,679. Frankfort Township, the Will County piece, holds $437,286,895. That puts roughly a fifth of Tinley Park's 2023 value on the Will side. A modest swing in the much larger Cook base moves a big share of the levy compared with what the Will side carries.

The Assessor's own estimates show the two Cook townships aren't moving the same way. For single-family homes, Orland's 2026 Assessor estimate is $408,000 against a 2025 median sale price of $405,000. Bremen's 2026 estimate is $239,000 against a 2025 median sale price of $264,000. These are township-wide figures covering more than Tinley Park, so they won't predict any one house. Even so, Orland is the largest piece of the village's tax base, and its median estimate sits slightly above 2025 sales, while Bremen's sits below.

Questions Buyers Ask About the County Line

Does the November 6 deadline apply to me if I'm buying in Orland Township? The deadline covers the Assessor appeal window tied to the 2026 reassessment notice. Whether a buyer under contract can or should do anything about it depends on the transaction and who owns the property on that date. The Orland Township valuation page has the official details.

Is 2026 a reassessment year on the Will County side? Will County's last quadrennial reassessment was in 2023, according to Tinley Park's 2024 annual financial report, so on a four-year cycle the next general reassessment would fall after 2026. Frankfort Township's posted 2026 residential factor of 1.0415 still changes assessments for taxes payable in 2027.

When does the Will side get its bills? The Frankfort Township Assessor's site says Will County bills went out at the beginning of May 2026, with installments due in June and September.

This post is general information about how the tax process works. It isn't legal, tax or financial advice, so confirm your own situation with the assessor's office, a tax professional or an attorney.

If you're weighing a Tinley Park home on either side of the county line, the Michelle Madden team can pull the parcel's actual tax history, show you which township and county it falls in, and set it beside comparable sales before you write an offer. If you're selling, start with Get Your Home Value, and we'll show how your home's tax picture fits into the price buyers will pay.