Every fall, a few of our S corp owners with Illinois income ask us some version of the same question: “Should we be doing that Illinois PTE thing?”
It’s a fair question.
The election has been around since 2021, plenty of people mention it in passing, and very few walk you through what it actually does with your numbers.
The short version is that the Illinois pass-through entity tax lets your S corp pay the state income tax that you would otherwise pay personally. Illinois collects about the same amount either way. What changes is your federal return, and that’s where the decision gets made.
We wrote about the Wisconsin version of this election earlier this year. This one covers the Illinois rules, which work differently in a few places that matter, starting with what the tax is.
What Is the Illinois Pass-Through Entity Tax?
The Illinois pass-through entity (PTE) tax is an optional, entity-level income tax that S corporations and partnerships can elect to pay. The Illinois Department of Revenue describes it as an entity-level income tax at 4.95% of the business’s net income, available for tax years ending on or after December 31, 2021.
Normally, an S corp pays only the Illinois replacement tax at the business level. The income tax on its profit flows to you on a K-1, and you pay it on your personal return. When the S corp elects, it pays the 4.95% at the business level, and each shareholder gets a credit for their share on their own Illinois return. Since the Illinois individual income tax rate is also 4.95%, the credit generally lines up with the tax you would have paid on that income anyway. That’s one of the big differences from Wisconsin, where the entity-level tax is 7.9%.
The election was originally written into the law as temporary. It may surprise you that the end date is gone. The Department of Revenue says the expiration date for the PTE tax has been removed under Public Act 104-0453, so it’s still available for 2026 and beyond. The reason anyone bothers with it comes down to one federal limit.
The Election Works Around the Federal SALT Cap
The federal deduction for state and local taxes on your personal return is capped. Under the 2025 federal tax law, the cap for 2026 is $40,400, reduced once modified adjusted gross income passes $505,000, though never below $10,000. Property taxes, state income taxes and the rest all share that one limit.
When the S corp pays the tax instead, it’s a business expense. IRS Notice 2020-75 says the S corp deducts the payment in the year it’s made, and that payment doesn’t count against any shareholder’s SALT limit. That’s the entire mechanism: a limited personal deduction becomes an ordinary business deduction.
When the cap jumped from $10,000 to $40,000 last year, we told clients it was worth rerunning the numbers on their personal deductions, and the same goes for this election. An owner who clearly came out ahead under the old $10,000 cap may not anymore, and another owner may come out ahead for the first time. Who comes out ahead is the next question.
Who Benefits From the Illinois PTE Election, and Who Doesn’t?
The owners who usually benefit are the ones whose state income tax would otherwise go undeducted. That happens when your total state and local taxes run past the cap, or when your income is high enough that the cap phases down toward $10,000. It also happens if you take the standard deduction, since in that case none of your state income tax is deducted personally.
Say you own an S corp that earns all of its income in Illinois, and you already pay more in state and local taxes than the cap allows. If the S corp elects, it pays the PTE tax, deducts it on its federal return, and passes you a matching credit on your Schedule K-1-P to apply against your Illinois tax. Your Illinois bill looks about the same. Your federal taxable income is lower because the state tax was paid by the business instead of sitting above your cap.
The owners who may not gain much are the ones who itemize and whose property and state income taxes fit comfortably under the cap. Their state tax is already deductible, so the election adds paperwork without changing much. The entity deduction also changes other numbers on your federal return, so we always run the year both ways before recommending it.
One more thing to keep in mind: the election covers every shareholder at once. If you have co-owners with different situations, it can help one more than another, so it deserves a real conversation. That gets more involved when an owner lives in another state.
Wisconsin Owners With Illinois Income Need a Different Lens
If you live in Wisconsin and your S corp earns part of its income in Illinois, the PTE tax applies only to the share of the S corp’s income that’s apportioned to Illinois. The IL-1120-ST instructions build that into the PTE Income Worksheet, which multiplies business income by the S corp’s Illinois sales factor.
There’s an administrative upside, too. Illinois says a nonresident shareholder whose only Illinois income comes from the electing S corp, and whose credit covers their Illinois tax, doesn’t have to file an Illinois individual return. An electing S corp also stops owing pass-through withholding for nonresident owners.
The Department of Revenue also says a nonresident may be able to take a credit for taxes paid to Illinois on their home state return. How your home state treats a tax that the business paid, rather than you, is one of the things we check before recommending the election. Illinois residents, on the other hand, still file their own return and claim the credit there. Once you know who’s affected, the mechanics are fairly simple.
How the Election Is Made and Paid on the IL-1120-ST
The election is made each year by checking Line L in Step 1 of Form IL-1120-ST, the S corp’s Illinois return. It’s an annual decision, and Illinois says it becomes irrevocable after the extended due date for that year. So you get a fresh decision every year, and nobody should treat last year’s answer as automatic.
Payment works differently from the filing deadline. The instructions say the PTE tax has to be paid in full by the original due date of the return, generally the 15th day of the third month after year-end, even if the return itself is on extension.
Once the business elects, it also has to make quarterly estimated payments whenever it expects more than $500 of total Illinois tax for the year. Those are due on the 15th day of the 4th, 6th, 9th, and 12th months of the tax year. Larger liabilities have to be paid electronically. The payments themselves matter more than most owners realize.
The Credit Only Counts If the S Corp Actually Paid
The credit you claim on your personal return is capped at what the S corp really paid. The IL-1120-ST instructions say the PTE credit allocated to shareholders can’t exceed the PTE liability reported and actually paid by the S corp.
We met a business owner whose prior accountant had filed their state return as if the business had paid in at the entity level, when it never had. They were expecting a credit, and instead they got a letter saying it was wiped out, with no warning from the firm. That’s the kind of thing that happens when the business returns and the owners’ returns are handled as two separate jobs.
We think of your business income and your personal income as the same story. When we prepare the S corp return, we also know what’s on your personal return, so the election, the payments and the credits all match. Illinois also has the S corp add the PTE tax back on its Illinois return, which is one more detail that has to line up. The last piece is timing.
What Should You Settle Before December 31?
The biggest year-end question is when the PTE tax gets paid. Because the federal deduction belongs to the year the S corp pays, a December estimate counts toward the 2026 federal return, and a payment made with the return next spring counts toward 2027.
Before the year closes, we’d want answers to a few things. Is the projection for 2026 good enough to size the remaining payment? Does the business have the cash to make it without squeezing January payroll? Do all the shareholders understand the election and how their credit will show up? And has anyone compared the result with and without the election this year, at your actual income?
None of this needs to be decided in a rush. It does need to be decided with real numbers, which is why we fold it into the year-round tax planning we do with clients, alongside monthly reviews and cash flow forecasting.
Talk Through the Illinois PTE Election With Us
This is general education, and the right answer for your S corp depends on your income, where you and your co-owners live, and how you file personally. If you’d like a second set of eyes before the year closes, reach out to us, and we’ll run your numbers both ways.
If you liked this one, you’ll probably also like our post on proactive tax planning before year-end.
Until next time.
About Affinity Accounting
Affinity Accounting is a productized advisory firm serving owner-led service businesses ($1M-$15M revenue) in Milwaukee and Chicago. We deliver monthly accounting, tax strategy, and fractional CFO advisory on a fixed monthly fee.
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