How to Appeal Your Property Taxes in Kendall County, IL (and When Is the Appeal Deadline?)

by Brian Wittman

Getting your assessment right is one of the few tax fights you can win on your own. The form is free. The office is in Yorkville. You don't need a lawyer, and you don't need an appraisal.

Here's what you may not realize. Kendall County doesn't give each township its own window. It sets one date for the whole county, about 30 days after it publishes the new values, and once that date passes the Board of Review can't take your complaint at all.

Say your house is assessed $30,000 higher than it would sell for. At the 2025 rate in the Plainfield South area of Joliet, which sits in Kendall County, that's about $690 a year in property tax on value your house doesn't have. Miss the window and you pay it. Next year's window doesn't refund this year's bill.

How do I appeal my Kendall County property taxes?

File a written complaint with the Kendall County Board of Review on the county's own appeal form, with the comparable sales grid filled in, by the countywide deadline, and send every piece of evidence with it. The deadline is 30 days after the county publishes the year's assessments. For 2026 values, it's October 19, 2026, and the Board of Review's own rules say emailed or faxed copies won't be accepted. There's no fee listed on the form or in the rules.

Which tax bill are you actually appealing?

This trips up almost everybody, so it's worth one minute.

The bill you paid this summer was built on your 2025 assessment. The appeal window open right now is for your 2026 assessment, and that one becomes the bill you pay in 2027. Kendall bills come out in May and are due in two installments, early June and early September of the following year.

So if this year's bill felt high, you can't fight that bill anymore. What you can do is make sure the number it grew from is right before it turns into next year's bill.

And one more thing before you start. You can't appeal the tax rate. The rate is the sum of every taxing body on your bill, from the school district to the library. What you can appeal is the assessed value the rate gets multiplied by. That's the whole fight.

Why is there only one deadline in Kendall County?

Illinois law gives you 30 calendar days from the date the county publishes its assessment list. Every county outside Cook works off that rule. What changes is how each county publishes.

Kendall publishes for every township at once, so everybody gets the same date. In 2026, the new values were published September 17. Thirty days lands on a Saturday, so the deadline rolled to Monday, October 19. The county's assessment site, the 2026 Board of Review rules and the township assessors all say the same thing.

That's not how it works next door. In Grundy County, each township's list publishes on its own schedule, so the deadline floats. If you own in both counties, or you just moved from one to the other, don't assume the dates match. The Grundy County appeal process works on that floating date, and it's easy to miss for exactly that reason.

How do you find next year's deadline?

Look on the Kendall County assessment website after your township publishes. The county posts the final filing date right on its home page, and it updates every year. Publication typically lands in mid-September, which puts the deadline in mid-October, but that's a pattern, not a promise.

Don't wait for the date to show up in the mail. The 30 days start when the list is published, not when you notice it.

Is your house actually in Kendall County?

Check before you file anything. A lot of Kendall County homes don't have a Kendall County town on the envelope.

Joliet is the biggest example. Neighborhoods like Greywall Club and Lakewood Prairie carry Joliet mailing addresses, but they sit in Na-Au-Say and Seward townships in Kendall County. Same story for parts of Plainfield and Minooka. If you're weighing a move to Minooka, IL, the county line runs right through town, and it decides which Board of Review you'd file with.

The fastest check is your tax bill. Your parcel number and your township are printed on it. If the bill came from the Kendall County Treasurer, you're in the right place. If it came from Will or Grundy, you're not, and how to appeal your property taxes in Will County is the process you want instead.

Who is your township assessor in Kendall County?

Each Kendall township has an assessor, and that office sets the starting value before the county ever sees it. A few of them share one office. The state certifies Lisbon, Seward and Na-Au-Say as a single multi-township assessment district, which is why some Joliet and Minooka bills show a line called "Multi-Twp Assmt Dist."

Before you file, call your assessor. You don't have to. But some of them will look at your comparables and fix an obvious error right at the counter, which saves you the hearing. For 2026, the Kendall Township assessor asked for comparables by October 12 so there was time to review them before the formal deadline. Ask yours about their cutoff.

While you're on the phone, ask for your property record card. That's the sheet the assessor uses to value your house: square footage, bedrooms, bathrooms, basement finish, garage. If it says you have a finished basement and you don't, you've found your appeal.

What counts as a reason to appeal?

There are really two good ones.

The facts on your record card are wrong. Wrong square footage, a phantom bathroom, a finished basement that's still bare concrete. These are the easiest wins, because you're not arguing about value. You're correcting a record.

Your assessment implies a value higher than your house would sell for. Outside Cook County, the assessed value is meant to be about one third of market value. So multiply your assessment by three. If that number is more than your house would realistically sell for, and you can show sales that prove it, you've got a case.

What doesn't count: your taxes went up, your neighbor pays less, or you think the rate is too high. None of those are about your assessed value, and the Board of Review can only rule on that.

What evidence do you have to send with it?

Kendall is strict about this, and it's where most homeowners lose before the hearing even starts.

The comparable sales grid on page 2 of the residential form has to be filled out. The rules don't make it optional.
Three comparable sales. For 2026 appeals, the sales have to fall between January 1, 2025 and July 1, 2026.
An appraisal is optional. If you use one, it has to be by a licensed Illinois appraiser with an effective date of January 1 of the assessment year, and a bound appraisal needs five copies.
Everything goes in with the complaint. You can't file now and send evidence later.
Your signature, or your attorney's authorization. Without it, no hearing gets scheduled.

Good comparables are the whole game, and they're where you'll spend your time. They should be close by, similar in size, age and style, and actually sold, not just listed. Knowing how to find comps for a property tax appeal matters more than anything else on this page, because the sales you throw out are as important as the ones you keep.

How do you actually file it?

Download the residential appeal form from the Kendall County assessment website, fill out both pages, attach your evidence, and get it to the Board of Review:

Kendall County Board of Review 504 S. Main St., Yorkville, IL 60560 630-553-4146

Hand-deliver it or use the county's drop box at 504 S. Main, and keep a copy with the date on it. If you mail it, send it early enough that it arrives before the deadline, and call the office first if you're cutting it close. Don't email it, and don't fax it. The rules say neither one counts.

One heads-up. Some websites still list the old courthouse address on Fox Street. The 2026 rules and forms use 504 S. Main.

What happens after you file?

The Board of Review mails you a hearing date. At the hearing, witnesses are sworn in, and you walk through your evidence. Show up. If you don't, the board says it'll take whatever action it considers legal and just, which isn't a sentence you want deciding your appeal.

Then you get a written decision in the mail.

If the Board of Review turns you down, you're not done. You have 30 days from the date on that written decision to take it to the Illinois Property Tax Appeal Board. There's no filing fee, you can represent yourself, and you can file by mail or online. It's worth knowing what happens if your property tax appeal is denied before you ever file, because the clock on that second step is short.

You can also go to circuit court instead, but you'd pick one path. Filing at the state board closes off the court route for the same valuation argument.

Is it worth the trouble?

Run your own number before you decide. It's quick.

Every $10,000 your house is over-assessed, in market value, costs you roughly $230 a year at the 2025 rate in the Plainfield South area of Joliet, and about $277 a year at the Lakewood Prairie rate on the Minooka side. Those are illustrative, before exemptions.

So a $5,000 error probably isn't worth an afternoon. A $40,000 error is close to $1,000 a year. And Kendall County's next general reassessment is 2027, so a value that's wrong now can follow your bill for a while if nobody catches it.

If you're planning to stay in the house five to ten years, that's the real math. A one-time afternoon against a mistake that repeats every year until someone fixes it.

The Bottom Line

Kendall County makes this simpler than most counties do. One deadline for everybody. One form. One office. No fee.

What it doesn't do is chase you. The window opens when the county publishes, it closes 30 days later, and the Board of Review can't take a complaint after that. Check your parcel's county, pull your record card, find three real sales, and get the whole package in before the date. Your 2026 assessment becomes your 2027 bill whether you look at it or not.

Last updated: October 2026

Frequently Asked Questions

When is the deadline to appeal property taxes in Kendall County?

It's 30 days after the county publishes the year's assessments, and it's the same date for every township. For 2026 assessments, the deadline is October 19, 2026. The county posts the final filing date on its assessment website each year.

Can I appeal my Kendall County property taxes online?

No. The Board of Review takes its own written forms, and its rules say emailed or faxed copies won't be accepted. Hand it in, use the drop box at 504 S. Main St., or mail it early enough to arrive on time.

Does it cost anything to appeal?

The 2026 Kendall County appeal form and Board of Review rules don't list any filing fee. Your cost is your time and, if you choose to get one, an appraisal.

Do I need a lawyer or an appraisal to appeal?

No. A homeowner with an accurate record card and three solid comparable sales can file alone. An appraisal is optional, but if you use one, it has to meet the Board of Review's rules on date and license.

I have a Joliet address. Do I appeal in Kendall County or Will County?

It depends on your parcel, not your address. Parts of Joliet, Plainfield and Minooka sit in Kendall County. Your tax bill shows your parcel number and township, and the county that sent the bill is the county you appeal in.

Can I appeal my tax rate?

No. The rate is set by the taxing bodies on your bill. You can only appeal the assessed value the rate is applied to, which is why the evidence is all about what your house would sell for.

If you'd rather hand the whole thing off to someone who handles appeals for a living, reach out and I'll give you a referral.

Pulling comparable sales is part of what I do every week as a broker. Set up a time and I'll pull the recent sales around your Kendall County address so you know whether you have a case before the Board of Review deadline.

Brian Wittman is a licensed real estate broker (Real Broker LLC), mortgage loan originator (NMLS #2646598, NEXA Mortgage, LLC, Equal Housing Lender), and life insurance producer (Levinson & Associates). This article is for educational purposes only and is not financial, lending, tax, or legal advice, an offer, or a commitment to lend; all loans are subject to credit approval. Information is accurate as of the publication date; for current details and full disclosures, visit https://bluejeanbroker.com/disclosures.