Illinois IL-941: How to File, Deadlines & Requirements (2026)

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If you withhold Illinois income tax from anyone’s paycheck, Form IL-941 is how you report it. Get the timing or attachments wrong, and you’re looking at penalties and back-and-forth with the Illinois Department of Revenue (IDOR). This guide covers who must file, 2026 deadlines, payment schedules, Schedule P, e-filing, amendments, and penalties. TaxBandits supports Illinois payroll filings, including IL-941, UI-3/40, and new hire reporting.

What is Form IL-941?

Form IL-941, the Illinois Withholding Income Tax Return, reports Illinois income tax withheld from wages and other reportable payments, broken out by month within the quarter.

Filing and paying aren’t the same thing. IL-941 tells IDOR how much you withheld. You remit that money separately, through Form IL-501 or electronic payment, on a schedule tied to your payment frequency.

Illinois withholds at a flat 4.95%, and the 2026 personal exemption/allowance is $2,925, up from $2,850 in 2025. Those two numbers, along with the 2026 IL-700-T withholding tables, determine how much comes out of each paycheck.

Who Must File Form IL-941?

You must file if you withheld, or were required to withhold, Illinois income tax during the quarter on any of the following:

• Wages, salaries, bonuses, overtime, and commissions
• Non-wage income under a voluntary withholding agreement (pensions or annuities, for example)
• Illinois lottery winnings of $1,000 or more
• Gambling and sports wagering winnings subject to federal withholding (thresholds vary by wager type)
• Payments to purchase rights to Illinois lottery winnings

First, you’ll need a withholding account, setup through MyTax Illinois or by filing Form REG-1.

Deadlines & Payment Schedules

IL-941 is due on the last day of the month following each quarter. A weekend or holiday bumps the deadline to the next business day, which shifts two of the four 2026 dates:

Monthly vs. semi-weekly payment schedules

The return deadline and the payment deadline aren’t the same thing. How often you remit withheld tax depends on your payment schedule, based on a look-back period of July 1, 2024 through June 30, 2025 for 2026.

Monthly payers withheld $12,000 or less during the look-back period, or they’re new filers by default.

• Deposits are due by the 15th of the following month
• Payment is made electronically or by IL-501 coupon

Semi-weekly payers withheld more than $12,000 during the look-back period.

• Amounts withheld Wednesday through Friday are due the following Wednesday
• Amounts withheld Saturday through Tuesday are due the following Friday
• Payment must be electronic

How to File Form IL-941?

Illinois requires e-filing. You have two main options:

1. MyTax Illinois, the state’s portal, handles the return, Schedule P upload (with CSV import), and payment in one place.
2. IDOR-approved third-party software, like TaxBandits, useful if you’re juggling other Illinois payroll forms.

Typically, Form IL-941 filing involves the following steps:

1. Gather withholding totals by month
2. Complete Line 2 using actual payment dates, not deposit dates
3. Reconcile payments and credits on Line 5
4. Attach Schedule P
5. Submit with payment

Schedule P: What It Is and Why It’s Mandatory

Schedule P, the Illinois Withholding Schedule, has to accompany every IL-941, even in a zero-withholding quarter (just complete it with zeros).

It lists, for each employee or payee:

• Name
• Social Security number
• Illinois income subject to withholding
• Amount withheld

Year-End Reconciliation & Related Filings

There’s no standalone annual IL-941, but you’ll still reconcile year-end wage statements against what you reported quarterly. Total withholding on W-2, 1099, and W-2G forms should match your Line 2 and Line 5 totals across all four quarterly filings.

For filings due in 2026:

• W-2: e-file by February 2
• W-2G: e-file by March 31
• 1099-K: e-file by March 31 (required if the IRS requires it, or if there were four or more separate transactions totaling over $1,000)

Correcting a Return

Made a mistake on a previously filed IL-941? File Form IL-941-X, the Amended Illinois Withholding Income Tax Return, with the corrected figures. Common triggers include math errors, missed payees, or wage corrections discovered later.

Penalties & Interest

Good news: IDOR bills penalties and interest separately, so you don’t compute them yourself. Late filing, late payment, or underpayment typically triggers them. Staying on the correct payment schedule and paying electronically when required is the best way to avoid them. Check IDOR’s Publication 103 for specific rates.

What’s New for 2026

A few changes are worth flagging this year:

• The personal exemption/allowance rose to $2,925, effective for pay periods beginning on or after January 1, 2026, flowing through to the IL-700-T tables
• Two new withholding credits took effect: the REV Illinois credit and the MICRO Illinois credit, for tax years beginning on or after January 1, 2025
• Under Public Act 104-0453, production companies (or their payroll providers) must now withhold on compensation paid to a loan-out company for Illinois services

How TaxBandits Helps

Illinois payroll compliance means juggling quarterly IL-941 deadlines, Schedule P data, mandatory e-filing, and filings like UI-3/40 and new hire reports. TaxBandits brings it together with guided e-filing for IL-941, built-in Schedule P support (including bulk upload), deadline reminders, and coverage for the other Illinois payroll forms you need.

Ready to simplify your Illinois payroll filings?

FAQ

Is IL-941 filed monthly or quarterly? 

Quarterly. Payments may be monthly or semi-weekly, but you file the return four times a year.

Do I file if I withheld no tax? 

Yes, every quarter your account is open, even if reported with zeros.

Is there an annual IL-941? 

No. Illinois discontinued annual filing, and it’s quarterly only.

Do I have to e-file? 

Yes, unless you have an approved Form IL-900-EW waiver.

What’s the 2026 withholding rate? 

4.95 percent.

What are the 2026 due dates? 

April 30, July 31, and November 2, 2026, and February 1, 2027.

Monthly vs. semi-weekly? 

$12,000 or less in the look-back period puts you on monthly; more puts you on semi-weekly.

How do I correct an IL-941? 

File Form IL-941-X with the corrected withholding figures.