It is the question that comes up at almost every kitchen table we sit at, usually about ten seconds after the number does: "If we do this, what happens to our taxes?"
It deserves a real answer, because the two versions homeowners usually hear are both wrong. One says a remodel is a tax trap that quietly costs you for the rest of the time you own the house. The other says nobody ever really finds out. In Illinois, your township assessor almost certainly will find out — and the increase is almost certainly smaller and slower than you are picturing, because state law includes a four-year cushion written for people doing exactly what you are doing.
Here is how the process actually runs in Naperville and across DuPage, Will and Kane counties: who sets the number, what they look at, what the home improvement exemption does and does not cover, and when any of it reaches a bill. None of this is tax advice — your township assessor's office is the authority on your parcel, and a CPA or a property tax attorney is the right call for anything unusual. But knowing the sequence lets you put a realistic line in the budget instead of a vague worry.
Start With How an Illinois Tax Bill Is Actually Built
Almost every misunderstanding here begins with the same assumption: that your tax bill is a percentage of what your house is worth. It is not. It is your share of what your local taxing bodies asked for.
The chain runs like this. Your township assessor sets a fair cash value for the property — an estimate of market value. Outside Cook County, the assessed value is one third of that: the statutory level of assessment in Illinois is 33 1/3 percent of fair cash value. A state equalization factor is applied to produce the equalized assessed value, or EAV. Your homestead exemptions come off the EAV. Only then is a tax rate applied — and that rate is set by dividing what your schools, municipality, park district, library and county levied by the total EAV of the district.
Two consequences follow, and they matter more than anything else in this article.
First, assessed value is one third of market value. An improvement that adds $60,000 of fair cash value adds roughly $20,000 of assessed value, not $60,000. Homeowners routinely picture the wrong number by a factor of three.
Second, the rate floats. Because the rate is levy driven, an assessment increase does not lift your bill by the same proportion. What lifts your bill is your assessment rising faster than your neighbors'. If every house in the township moved the same amount and the levies did not change, the rate would fall and the bills would land in roughly the same place. Your remodel changes your share of a pie whose size was set by the levy, not by your kitchen.
What the Assessor Picks Up, and How
Township assessors review building permit records as part of their annual revaluation work, alongside recent sales and other changes to the property. In plain terms: pulling a permit is how the assessor finds out you built something.
That is not an argument for skipping the permit, and we want to be blunt about it. Unpermitted work surfaces anyway — at resale, at refinance, in aerial imagery, in the next general reassessment — and it surfaces at the worst possible moment, with a buyer's attorney asking why the finished lower level is not on the property record card. Our DuPage and Will County remodeling permit guide covers what unpermitted work costs a homeowner at closing, and the tax question is nowhere near the largest exposure there.
What the assessor is looking for is a physical change that affects value: finished square footage where there was none, an added bathroom, an addition, a converted attic or basement, a new garage. The property record card is updated to match what is actually standing there.
Not everything you spend moves the number
This is where homeowners over-worry. Assessors value the house, not the invoice.
- Maintenance and repair is not an improvement. Will County's assessment office states it directly: maintenance or repair work does not qualify — only new improvements, or rebuilding after a catastrophic event. Replacing a failing roof or a dead furnace is not the same category of event as adding a bedroom.
- Finish level is not square footage. Moving from laminate to quartz, or from builder-grade to custom cabinetry, changes what you spend far more than it changes a mass-appraisal valuation. The two numbers are not proportional.
- New living area is the real mover. Additions, attic and basement conversions, and added bathrooms are the changes that reliably show up on a property record card, because they change the physical description of the house.
The Home Improvement Exemption Is the Part Most Homeowners Miss
Illinois has a provision written for exactly this situation, and in our experience most homeowners planning a remodel have never heard of it.
Under 35 ILCS 200/15-180, the homestead improvement exemption shields the increase in value created by a new improvement to your principal residence — up to $75,000 of fair cash value per year, which is $25,000 in assessed value — for four years from the date the improvement is completed and occupied.
Read what that actually does. If your project adds $75,000 or less of market value to the house, the value it added is exempt for four years. You are not dodging anything; the legislature decided that a homeowner who improves their own house should not be taxed on that improvement immediately. In year five, the sheltered value comes onto the rolls and the bill reflects it.
The limits worth knowing:
- It applies to homestead property — your principal residence, not a rental or a second home.
- The four-year clock runs from completion and occupancy, not from the date you file anything.
- The $75,000 is an annual maximum, and you cannot receive the exemption on another Illinois property in the same assessment year.
- It shelters only the increase attributable to the improvement. The rest of your assessment keeps moving with the market underneath it.
- Maintenance and repair do not qualify, which is the same line drawn above.
Naperville Sits in Two Counties, and the Paperwork Differs
Here is the local wrinkle, and it is specific to this market in a way that catches even long-time residents.
Naperville is not in one county. The City spans DuPage and Will, and it is covered by six townships: Lisle, Milton, Naperville and Winfield in DuPage County, and DuPage and Wheatland townships in Will County. Two houses a few streets apart can be in different counties, under different assessment offices, with different procedures for the same exemption.
DuPage County — no form to file. The county's guidance is explicit: if the township assessor increases the assessed value on an eligible property as the result of a physical change to the home, the assessor will automatically initiate the exemption on behalf of the taxpayer, and it is then automatically renewed over the following three years. DuPage describes the maximum deduction as $25,000 of assessed value.
Will County — you apply. The Supervisor of Assessments directs homeowners to apply with their local township assessor; if you qualify, that assessor files the paperwork with the county office. Same $75,000 cap, same four years from completion and occupancy — but nobody starts it for you.
Kane County — no application either. Kane's assessment office states you need not file an application; the township assessor verifies the amount to the County Assessment Office. That is the relevant rule if you are building in Geneva, St. Charles, Batavia, Aurora or Montgomery.
Where a form is required, the state form is PTAX-323. The practical rule, wherever your house sits: when the project is finished, call your township assessor and ask whether the improvement exemption has been applied to your parcel. The call is free, it takes five minutes, and on the Will County side of Naperville it is the difference between having the exemption and not having it.
The Timing: Why the Bill Arrives Almost Two Years Later
Homeowners expect the tax consequence to arrive quickly. It does not, and understanding the calendar prevents a lot of unnecessary anxiety in the meantime.
Assessments in Illinois are made as of January 1 of the assessment year. In DuPage, township assessors are required to complete entry of their revaluation information into the county's assessment system by November 15 of that year. Change-of-assessment notices are mailed and assessment changes are published by township. The tax bills built on that assessment year are typically printed and mailed in the last week of April of the following year, with installments due June 1 and September 1.
So a kitchen finished in the spring of 2026 falls into the 2026 assessment year, is reviewed and entered by that November, and first appears on a bill mailed in the spring of 2027. If the improvement exemption applies, what appears is the portion that was not sheltered.
One more date worth marking. DuPage runs a general assessment year every four years, when every parcel is reviewed and every owner receives a notice. 2019 and 2023 were the last two, which puts the next one in 2027. If your project lands near that cycle, expect a notice whether or not you built anything — that one is the cycle, not your remodel.
If the New Assessment Looks Wrong
Assessors work from permits, sketches and property record cards, and paperwork produces paperwork errors: square footage counted twice, a powder room recorded as a full bath, a rec room and storage area recorded as finished living space.
You have a defined window to say so. Complaints go to the county Board of Review, and the filing period runs 30 days from the publication of the assessment list for your township. Publication dates are set township by township, so check your county assessment office for your township's posted deadline rather than assuming a date.
Before you file anything, do the cheap thing first: pull your property record card and read it. Confirm the square footage, the bath count, the basement finish description and the year of the improvement. A large share of the assessment complaints that succeed are corrections of fact, not arguments about market value — and a fact you can document is a much easier conversation than an opinion you have to defend.
How We Put This in a Budget
The practical version, the way we walk clients through it before a project starts:
- Assume any project that adds finished living area will eventually be assessed. Plan for it rather than hoping around it.
- Assume roughly one third of the added market value reaches assessed value — and that the first $75,000 of added value is sheltered for four years.
- Do not assume added market value equals what you spent. They are different numbers, and on high-finish work they are not close.
- Call your township assessor after completion and confirm the exemption is on the parcel. On the Will County side, treat this as a required step.
- Never let the tax question push you toward unpermitted work. It is the most expensive way to save a small amount of money in this business.
And keep it in proportion. Across the projects we build in this market — a multi-room renovation like our Alyssa remodel in Naperville, a kitchen, a finished lower level — the property tax change is rarely the line that decides whether a project makes sense. The construction budget decides that. Our renovation budget guide for the western suburbs covers the current ranges by project type, and our guide to the hidden costs of remodeling covers the numbers that genuinely do surprise people.
Where the Conversation Starts
Every municipality in this market runs its own permit desk, and the permit is the first document in the chain that eventually reaches your assessor. In Naperville, that desk is the TED Business Group at (630) 420-6100, Monday through Friday, 9 a.m. to 4 p.m. In Geneva, the City's Building Division is at (630) 232-0032. Elsewhere, call the municipality your house is in — not the county — before anyone starts drawing.
Ask early who will apply for that permit. Our guide to hiring a remodeling contractor in Naperville covers that question along with the rest of the paperwork, from the written contract to lien waivers.
If you are weighing an addition, our guide to planning a home addition in Naperville covers the zoning and stormwater checks that decide what is buildable. If the lower level is the cheaper route to the same square footage, finishing a basement in Naperville walks the code side of that decision. The service pages for room additions, kitchen remodeling and basement finishing lay out how we scope each one, and our Naperville page and locations directory cover the towns we build in.
Frequently Asked Questions
Will a kitchen remodel raise my property taxes in Naperville?
Usually far less than homeowners expect, and often not at all in the first four years. A kitchen remodel that does not add square footage changes finish quality rather than the physical description of the house, and assessors value the property rather than your invoice. Where a remodel does add value, the Illinois homestead improvement exemption shelters up to $75,000 of that added fair cash value for four years from completion and occupancy. Adding finished living area — an addition, a converted attic, a new bathroom — is what reliably moves an assessment.
What is the Illinois home improvement exemption?
It is a homestead exemption under 35 ILCS 200/15-180 that shields the increase in value created by a new improvement to your principal residence, up to $75,000 of fair cash value per year, which equals $25,000 of assessed value at Illinois's 33 1/3 percent assessment level. It runs for four years from the date the improvement is completed and occupied. It does not apply to maintenance or repair work, and you cannot receive it on another Illinois property in the same assessment year.
Do I have to apply for the home improvement exemption in DuPage County?
No. DuPage County's guidance is that if the township assessor increases the assessed value as the result of a physical change to the home, the assessor will automatically initiate the exemption on behalf of the taxpayer, and it is automatically renewed over the following three years. Kane County likewise states that no application is needed. Will County is different: the Supervisor of Assessments directs homeowners to apply with their local township assessor. Because Naperville spans DuPage and Will, which rule applies depends on which side of the county line your house is on.
How long after a remodel do property taxes go up?
Longer than most people assume. Illinois assessments are made as of January 1 of the assessment year, DuPage township assessors must enter their revaluation work by November 15 of that year, and the resulting tax bills are typically mailed in the last week of April the following year, with installments due June 1 and September 1. A project finished in spring 2026 therefore first shows up on a bill in spring 2027 — and if the improvement exemption applies, only the unsheltered portion shows up at all.
Can I avoid a tax increase by not pulling a permit?
No, and it is a bad trade. Unpermitted work still surfaces at resale, at refinance, in aerial imagery and at the next general reassessment, and it surfaces in front of a buyer's attorney rather than in front of your assessor. It can also complicate insurance claims and force retroactive correction of work that is already closed up. Given that the improvement exemption shelters up to $75,000 of added value for four years anyway, the amount being avoided is usually small relative to what unpermitted work costs at closing.
Have a question we haven't covered? Our remodeling FAQ page answers the broader set, or tell us what you're planning and we'll scope it honestly — including what it does and doesn't do to the line items you'll still be paying in five years.