A buyer under contract on a home near Route 59 got her Closing Disclosure two weeks before closing. The seller's attorney had prorated property taxes at 105 percent of the most recent bill, standard practice for most of Illinois. Her attorney sent it back. The house sat in Hanover Township, the Cook County slice of Bartlett, where the customary proration is 110 percent, not 105. The gap was a few hundred dollars, small enough to fix with one phone call, large enough that nobody wants to discover it at the closing table.
That phone call only happens because someone knew which county the house was in. Most buyers don't ask, because most towns don't require the question. Bartlett does.
Bartlett Is Three Tax Systems Wearing One Name
Bartlett sits across Cook, DuPage, and Kane counties, a genuine rarity among Chicago suburbs. A house on one street can carry a Cook County PIN while a house two blocks over carries a DuPage or Kane number, with no visual cue on the lot line to tell you which. The zip code doesn't sort it. The subdivision name doesn't sort it. Only the parcel number does.
That split shows up in real numbers, not just paperwork. Effective property tax rates run close to 2.89 percent on the Cook County side of Bartlett, versus about 2.73 percent in the DuPage County portion. On the Kane County side, published rates land in the high 2.8 to 2.9 percent range depending on the source and snapshot date, with one county-wide comparison naming Bartlett the highest rate in Kane County at 2.80 percent. None of these numbers is dramatically higher than the others in isolation. Stacked against different median home prices in each county pocket, they add up to genuinely different ownership costs for houses that a listing photo would never distinguish.
The price spread reinforces the point. The median home price in Bartlett's DuPage County pocket runs around $314,070, while the Kane County pocket runs closer to $373,337. Same village, same school buses, same downtown, different math depending on which side of an invisible line the deed sits.
| Bartlett portion | Effective property tax rate | Median home price | Standard proration |
|---|---|---|---|
| Cook County (Hanover Township) | ~2.89% | varies by parcel | 110% |
| DuPage County | ~2.73% | ~$314,070 | 105% |
| Kane County | ~2.80–2.91% | ~$373,337 | 105% |
None of this is a reason to avoid one part of Bartlett over another. It's a reason to ask the question before you fall in love with a floor plan.
The Bill That's Landing This Summer
Here's what makes 2026 a worse year than usual to skip that question if you're buying or selling on the Cook County side.
Cook County reassesses property in thirds, on a rotating three-year cycle by geography. Hanover Township, which covers the Cook County portion of Bartlett, was reassessed in 2025. The Cook County Assessor's Office mailed reassessment notices to Hanover Township homeowners on November 6, 2025, with an appeal deadline of December 22, 2025. Under Cook County's billing structure, the reassessed value shows up on the second installment tax bill the following year, which Hanover Township's own assessor's office estimated would arrive in July 2026, subject to change.
That means anyone closing on a Cook County side Bartlett home right now is buying into a freshly reassessed tax base before the bill that reflects it has even been mailed. Every prior real estate closing this cycle was working from a stable, three-year-old assessment. This year's closings are working from a number that's about to move, in either direction, and nobody signing the contract knows by how much until the new bill lands.
Why The Proration On Your Closing Disclosure Might Not Match The Real Bill
Illinois pays property taxes a year behind. The bill you receive in a given year covers the prior year's taxes, not the current one. That single fact is why every Illinois closing includes a tax proration credit at all: the seller owes the buyer money for taxes accrued during their ownership that haven't been billed yet, and that credit is built from the best available guess, not the final number.
The standard guess uses a percentage of the last known bill. Outside Cook County, that's typically 105 percent. Inside Cook County, it's typically 110 percent, because Cook County taxes have historically climbed faster year over year. Both are estimates. Neither is a guarantee.
In a normal year, the estimate holds up reasonably well because the underlying assessment hasn't changed. In a reassessment year, the estimate is built on a bill from before the reassessment, applied to a property whose assessed value is about to shift. A buyer who closes on a Hanover Township home this year, with a proration based on the pre-2025 bill, may find the real bill lands well above or below what the seller credited, once the reassessed value works its way into the second installment.
There's a second trap layered on top. Property tax exemptions in Cook County, including the homeowner exemption and senior exemption, follow the person, not the house. When a home sells, the seller's exemptions come off the bill, and the buyer has to apply for their own. If the proration was calculated using a bill that still reflected the seller's exemption, the buyer's real first-year bill can come in higher than the credit accounted for, independent of any reassessment at all.
Neither of these problems is unique to Bartlett. Illinois works this way everywhere. What's unique to Bartlett is that the answer to "does this apply to my closing" depends on which of three counties the parcel sits in, and this particular year, one of those three just had its assessed values reset.
What This Means With The Market Moving Fast
Bartlett's market hasn't been forgiving of slow decisions. As of August 2026, homes here carried a median list price around $414,990 and spent a median of about 13 days on the market, roughly 27 percent faster than the same month last year. A tighter window between an accepted offer and a signed contract means less time to catch a proration mismatch before it's baked into the paperwork, and more reason to raise the county question during attorney review rather than after.
What To Ask Before You Write An Offer
- Which county does this specific parcel sit in? Ask your agent or check the PIN before assuming based on address or school district.
- If it's in Hanover Township or elsewhere in Cook County, has the 2025 reassessment already changed the assessed value, and has the new tax bill been issued yet?
- What proration percentage does the contract use, 105 or 110, and does that match the property's actual county?
- Did the seller carry a homeowner or senior exemption, and does the proration account for that exemption disappearing after closing?
- Is there a reproration clause in the contract, so both sides can true up the number once the real bill arrives?
None of these questions require a lawyer to ask out loud. They just require someone in the transaction to know that Bartlett isn't one tax system pretending to be complicated. It's three tax systems that happen to share a village hall.
A Few Common Questions
Does my subdivision tell me which county I'm in? Not reliably. Subdivision names and school attendance boundaries don't follow county lines in Bartlett. The parcel number is the only definitive source.
Do all three counties use the same tax bill schedule? No. Cook County bills in two installments, with the second installment reflecting any reassessment from the prior year. The collar counties, including DuPage and Kane, follow a similar arrears principle with their own billing calendars.
If I'm buying in the DuPage or Kane portion of Bartlett, does any of this apply to me? The reassessment timing is specific to Hanover Township's Cook County cycle, but the underlying proration logic, arrears billing and exemption disappearance, applies statewide. The percentage your attorney should use is the part that changes by county.
Bartlett rewards buyers and sellers who ask one extra question before the ink dries. If you're weighing a home here and want someone who already knows which side of the line it sits on, The Luxury Connection Home Team can walk through the numbers with you. Schedule a consultation before you write the offer, not after.
