Why would two houses half a mile apart, both carrying a Naperville mailing address, arrive at closing with property tax bills that differ by more than a thousand dollars a year even though they sold for close to the same price? The listing agent didn't make a mistake. The county did, or rather, the county line did, because it cuts across the southern part of the city and splits it in ways that never show up on a listing sheet.
Naperville sits inside two counties. Most of the city falls in DuPage County, but a meaningful slice of the south side falls in Will County, and each county sends its own tax bill through its own treasurer's office. On top of that, the city's two school districts, Naperville Community Unit School District 203 and Indian Prairie School District 204, draw their boundaries around enrollment and feeder patterns rather than around the county line or the city limits. A buyer comparing two homes under one city name is often comparing two different administrative systems layered on top of each other, and the "median" figure that shows up on a valuation estimate is really an average across both of them.
One City, Two County Treasurers
Property tax records for Naperville parcels are kept in two separate places. Most addresses fall in DuPage County, which handles the majority of the city's tax rolls, but homes on the south side can just as easily land in Will County, with its own assessor, its own Board of Review, and its own treasurer collecting the payment. The rates aren't close. Naperville's DuPage County portion carries a median effective property tax rate of about 2.05 percent, while the Will County portion runs closer to 2.35 percent, both measured against Illinois' statewide median of 2.33 percent.
On a $650,000 home, that 0.30 percentage point gap works out to roughly $1,950 a year, or about $162 a month, purely as a function of which side of an invisible line the parcel happens to sit on. It has nothing to do with the home's condition, its square footage, or how recently it was updated.
There's a second layer to this that catches even careful buyers off guard. Naperville Township, the local governing body responsible for assessing property values before they reach the county, doesn't track the city limits either. Its own office notes that if you live in the City of Aurora but sit east of the Kane County border, you're probably still inside Naperville Township, meaning the taxing bodies attached to your bill can carry the Naperville name even when your mailing address doesn't. A "Naperville" tax bill and a "Naperville" address aren't guaranteed to be the same thing.
Even the Zip Code Isn't a Safe Shortcut
The instinct once a buyer learns about the county split is to use zip code as a stand-in, on the assumption that at least a zip code is a fixed, contiguous area. It isn't, not here. Effective tax rate data broken out by zip code shows 60563 running a median rate of 2.03 percent while 60564 runs 2.23 percent, a 0.20 point spread entirely within the DuPage County side of the city. Meanwhile, the same 60564 zip code shows up again in Will County's records, this time carrying a median effective rate of 2.37 percent, alongside 60540 at 2.13 percent.
That means 60564 isn't one number. Part of it sits in DuPage, part of it sits in Will, and the two halves carry different rates from different counties. A buyer who narrows a search to "60564" because a friend mentioned the zip code is still going to need the specific parcel before the tax number means anything.
Here's what that looks like translated into dollars on a $650,000 home:
| County | Zip Code | Median Effective Rate | Illustrative Annual Tax |
|---|---|---|---|
| DuPage | 60563 | 2.03% | ~$13,195 |
| DuPage | 60564 | 2.23% | ~$14,495 |
| Will | 60540 | 2.13% | ~$13,845 |
| Will | 60564 | 2.37% | ~$15,405 |
Zip code 60564 appears in both rows because it spans the county line. The swing between the cheapest and most expensive combination in this table, all under the same city name, comes to more than $2,200 a year, wider than the gap between the two counties on their own.
School District Lines Don't Follow the County Either
Layer the school districts on top and the picture gets more particular still. District 203 and Indian Prairie District 204 assign students by address, and their boundaries were drawn around enrollment and feeder paths rather than around the DuPage-Will line or the city limits. A single street can be split between the two districts, which is why local guidance consistently warns buyers never to assume a home's district from the house next door.
District 203 serves roughly 16,000 students across central and northern Naperville, including small portions of neighboring Lisle and Bolingbrook, and its two high schools are Naperville Central and Naperville North. District 204 is considerably larger, stretching into Aurora, Bolingbrook, and Plainfield, and feeding Neuqua Valley, Metea Valley, and Waubonsie Valley high schools. Both districts publish their own boundary tools, District 203's at naperville203.org and District 204's at ipsd.org, and both maintain enrollment offices that will confirm the exact assignment for a specific address before a buyer writes an offer.
None of this is about which district serves a family better. It's that a home's district, like its county and its township, is a property of the parcel, not the city name printed on the envelope.
What the Headline Median Is Actually Averaging
This is why a single "Naperville" number, whether it's a median sale price or a median tax bill, tends to understate how much variation sits underneath it. A Q4 2025 analysis of Naperville sales, drawn from BlockShopper data and reported by DuPage Policy Journal, put the city's median sale price at $653,000 across 98 transactions, with a median tax bill of $13,141, more than double the national average effective rate. That single median bill is the blend of every DuPage parcel and every Will County parcel, every 203-zoned lot and every 204-zoned lot, averaged into one number that describes no specific house particularly well.
Buyers comparing named subdivisions like Ashbury, White Eagle, Tall Grass, or the streets closer to downtown and the Riverwalk are, in effect, comparing pockets that can sit on different sides of these lines even when the subdivision names suggest a single, uniform community. The subdivision name is a marketing label. The county, township, and school assignment are matters of record tied to the parcel itself.
Checking Which Side of the Line a Home Sits On
Before treating any Naperville tax estimate as final, it's worth confirming four things at the parcel level rather than the zip code or subdivision level.
- Pull the property's PIN and confirm whether it's recorded with DuPage County or Will County. DuPage County's own property lookup tool covers parcels on that side of the city.
- Ask for the seller's current, actual tax bill rather than an estimate based on a comparable sale, since the comparable may sit across the line.
- Confirm the school district assignment directly through the district's own boundary tool rather than assuming it from a neighboring address.
- Check whether the parcel carries a special service area or other local assessment layered on top of the base rate, since these vary by subdivision even within the same county.
Naperville Township's assessor office publishes side by side examples of how a typical tax bill breaks down for a home in Aurora within District 204 compared to one in Naperville within District 203, which is a useful gut check before assuming any two "Naperville" bills look alike.
A Couple of Questions Worth Settling Early
Does a Naperville zip code tell me which county a home is in? Not reliably. Zip code 60564 has parcels recorded in both DuPage and Will counties, each carrying a different median effective tax rate. The zip code narrows the search. It doesn't answer the question.
Can a buyer choose which school district a Naperville home feeds into? No. Assignment runs with the parcel's address, and boundaries between District 203 and District 204 don't align with the county line or with subdivision names. The only reliable way to confirm assignment for a specific home is through the district's own boundary tool before writing an offer.
Working through which county, township, and school boundary apply to a specific Naperville parcel is exactly the kind of detail that's easy to miss when comparing listings side by side. If you're weighing a move within Naperville or into it from elsewhere in the Fox Valley, The Kelly Schmidt Group can pull the parcel-level facts on a specific address before you get attached to a number that might belong to a different part of the city.
