Every Burr Ridge listing sheet carries a tax line: one dollar figure that buyers plug into their monthly payment math. On the Cook County side of the village, that figure comes from an assessment cycle that ended in 2023. A new valuation was mailed to owners on July 23, 2026, and it won't show up on a bill until 2027. On the DuPage County side, the figure comes from the same 2023 base plus annual adjustments, and on DuPage's four-year cycle the next full revaluation falls in 2027.
So two Burr Ridge homes at similar asking prices can be on very different tax paths. The tax figure on the listing sheet reflects valuations from the 2023 cycle and tells you nothing about the reset that's coming for either home.
The tax line is a snapshot of a cycle that already ended
Burr Ridge is the only village in our coverage area split by a county line. The Cook portion sits in Lyons Township, and the Cook County Assessor's August 1, 2026 release names Burr Ridge among the communities partly inside it. The Assessor reassesses one-third of the county each year, and the south and west suburbs were last reassessed in 2023. The same release says values certified in 2026 "will affect second-installment tax bills issued in 2027."
The DuPage portion sits in Downers Grove Township. The Illinois Department of Revenue's assessment guide says property outside Cook County must be revalued once every four years. DuPage County gives 2019 and 2023 as examples of general assessment years. Count four years forward from 2023 and the next one lands in 2027. In the years between, the county's Supervisor of Assessments looks at three years of township sales and applies an equalization factor across the township if one is needed.
Put side by side, the two calendars look like this:
| Cook side: Lyons Township | DuPage side: Downers Grove Township | |
|---|---|---|
| Last full revaluation | 2023 | 2023 |
| What happened in 2026 | Full reassessment, notices mailed July 23 | Uniform equalization factor of 1.0635 |
| 2026 Board of Review deadline | Friday, November 6, 2026 | Monday, November 2, 2026 |
| Next full revaluation | 2029, on the three-year cycle | 2027 |
| Latest bill timing | Tax Year 2025 second installment expected September 1, 2026, due October 1 | 2025 bills mailed April 29, 2026, due June 1 and September 1 |
The 2029 date comes from the Assessor's one-third-per-year rotation, counting forward from 2026. Everything else in the table comes straight from county sources.
The Cook side reset first, and it was top-heavy
On the Cook side, the 2026 reassessment was a big move. A Cook County property tax appeal firm, Cook County Tax Appeal, compiled the county's numbers and reported that the median Lyons Township home assessment rose 25.1% from 2025 final values to the 2026 notices. By its count, 96.9% of the township's 38,177 homes went up.
The more useful number for Burr Ridge is a different one. The same firm reported that total residential assessed value rose 29.6%, faster than the median, and concluded that increases were larger at the top of the market. It named Burr Ridge, along with Western Springs and Hinsdale, as places where owners should measure their increase against similar homes, not against the township figure. This is a private firm's analysis, not an official county release, but the math is simple. When the total rises faster than the median, the gains are concentrated in the higher-value homes.
That ties straight back to the listing sheet. For a Cook-side Burr Ridge home, the tax bill a seller paid in 2026 rests on the 2023 cycle. The value that will drive the 2027 bill is already printed on a reassessment notice that went out in July. Those are two different numbers, and in a top-heavy year the gap between them can be wider in Burr Ridge than in the township as a whole.
Why the township averages don't describe Burr Ridge
The Assessor's own Lyons Township residential valuation report shows a 2025 median single-family sale price of $462,000 and a 2026 Assessor median estimate of $418,000. Condos show $225,000 and $218,000. Those are fair figures for a township that also includes Lyons, Summit, Brookfield and Countryside. They aren't Burr Ridge figures.
According to MRED's Burr Ridge Local Market Update, the median detached sale price for the 12 months through September 2026 was $1,100,000, up 12.5% from the prior 12 months. The average was $1,416,744, up 32.2%. The average climbing much faster than the median shows the same top-end strength that the reassessment numbers point to. The expensive end of Burr Ridge's market has been moving faster than the middle.
The Assessor's report says each township is split into neighborhood codes, and owners can find theirs on the reassessment notice and the PIN detail page. For a Burr Ridge home, that neighborhood-level comparison is the one that matters. The township median sits at less than half of what a typical Burr Ridge house sells for.
The September median drop is mostly sample size
Anyone watching Burr Ridge prices this fall probably saw a scary number. MRED's September 2026 report puts the detached median at $885,000, down 28.0% from $1,230,000 in September 2025.
That median came from 14 closed sales. MRED's own footnote warns that "activity for one month can sometimes look extreme due to small sample size." The trailing 12-month median went up over the same stretch. With so few sales, a month's median mostly tells you which houses happened to close.
The September report does show a few other things:
- Detached homes sold in September 2026 brought 100.5% of original list price on average, up from 95.9% a year earlier.
- Average detached market time rose to 97 days from 36.
- Detached inventory at month end fell to 33 from 41.
- Attached inventory went from 1 home to 11, while attached market time fell to 22 days.
The attached side is where Burr Ridge buyers have suddenly gained options. The 12-month attached median held flat at $535,000.
The Assessor says Cook County assessments reflect market value "over the last three years." One soft September won't undo three years of top-end gains in the valuation.
What to pull before you compare two Burr Ridge houses
When a buyer is weighing a Cook-side home against a DuPage-side home, I want the tax picture for each one on paper, not the single listing-sheet number. Here's what I pull:
- The county and PIN. Cook PINs and DuPage parcel numbers look different. DuPage lists Downers Grove Township parcels under the 09 and 10 prefixes.
- On the Cook side, the 2026 reassessment value. This is the value the Assessor says will show up on the 2027 bill. Compare it with the value behind the most recent bill.
- On the DuPage side, the 2026 assessed value from the township. The Downers Grove Township Assessor's parcel search shows 2026 values that include the 1.0635 factor, with data updated September 30, 2026. Then keep 2027 in mind, because that's DuPage's next general revaluation.
- Whether an appeal is pending. On the Cook side, the Board of Review's Lyons window opened October 8 and closes Friday, November 6, 2026. There's no filing fee. On the DuPage side, the Board of Review deadline for Downers Grove Township was Monday, November 2, 2026. If a seller filed, the outcome may not be known until after you close.
- The bill calendar. Cook's Tax Year 2025 second installment was expected to mail September 1, 2026, and be due October 1. The county blamed the two-month delay on its tax-system technology overhaul. The year before, the second installment was expected November 14, 2025. DuPage's 2025 bills went out April 29, 2026. Cook's late bills move later every time the county's schedule slips.
Do this for both houses and the comparison changes. Two homes at the same price, one on each side of the county line, will each get a valuation reset, but at different times and through different processes. On one side the new value is already on paper. On the other, it's a year away.
FAQ
Does living on the DuPage side mean my taxes won't change? No. DuPage applied a 1.0635 equalization factor to Downers Grove Township assessments in 2026, and the county's four-year cycle puts the next general revaluation in 2027.
When does the Cook-side 2026 reassessment show up on a bill? The Assessor says values certified in 2026 affect second-installment bills issued in 2027.
Is the September price drop a sign Burr Ridge values are falling? The September 2026 median of $885,000 came from 14 detached sales. The 12-month median through September rose 12.5% to $1,100,000.
This post is general information about county calendars and published figures, not legal, tax or financial advice. Check your own property's situation with a tax professional or attorney before you act on an assessment or an appeal.
If you're pricing a Burr Ridge home on either side of the county line, the 2027 tax picture belongs in the list price and the buyer conversation from day one. Francesco Campobasso will pull both county records for your parcel and build them into your pricing plan. Get Your Free Home Valuation.
