Illinois Withholding Tax: IL-941, W-2s, and Deposits

Illinois withholding tax is a flat 4.95% that employers must deduct from wages, deposit with the Illinois Department of Revenue on a monthly or semi-weekly schedule, and reconcile through quarterly Form IL-941 returns and year-end electronic W-2 filings.¹ The obligation attaches to the employer, not the worker: if you fail to withhold, you still owe the tax out of your own funds.²

How to Calculate the Withholding

For each pay period, subtract the employee’s exemption amount from gross wages, then multiply the result by 0.0495. The personal exemption is $2,925 per year in 2026, up from $2,850 in 2025.³ Booklet IL-700-T breaks that annual exemption down into weekly, biweekly, semi-monthly, and monthly amounts so you can apply it directly to each paycheck.¹

Because Illinois has no graduated brackets, bonuses, commissions, and overtime are withheld at the same 4.95% as regular wages. There is no separate supplemental rate.¹

Registering and Collecting IL-W-4s

Before you issue a single paycheck, get a withholding tax account number from IDOR. You can register online through MyTax Illinois or submit a paper REG-1 (Illinois Business Registration Application).⁴ The online route lets you file returns and make payments through the same portal. You’ll also need to register separately with the Illinois Department of Employment Security for unemployment insurance.

Each employee must complete Form IL-W-4 on or before their first day of work. It tells you how many allowances to apply. Employees may file a new IL-W-4 anytime allowances increase; if allowances decrease, they must file a new form within 10 days. The death of a spouse or dependent does not change allowances until the following tax year.⁵

Higher earners need a closer look. Employees with adjusted gross income above $500,000 (married filing jointly) or $250,000 (all other filers) may lose eligibility for the personal exemption or certain additional allowances and should update their IL-W-4 to increase withholding accordingly.⁵

Monthly or Semi-Weekly Deposits

IDOR puts every employer on one of two deposit schedules based on how much withholding you reported during a look-back period ending June 30 of the prior year. The dividing line is $12,000.⁶

Monthly schedule. First-time employers, and any employer that reported $12,000 or less during the look-back period, use Form IL-501. Payments are due by the 15th of the month following the month the tax was withheld.
Semi-weekly schedule. Employers that reported more than $12,000 pay on Wednesdays (for tax withheld the previous Wednesday through Friday) and on Fridays (for tax withheld the previous Saturday through Tuesday). Semi-weekly payments must be made by electronic funds transfer.

Growth mid-year matters. If you cross $12,000 during any quarter, you must switch to the semi-weekly schedule for the rest of that quarter, the remainder of the year, and the following year.⁶ Track your running totals.

Quarterly IL-941 Returns

Every employer files Form IL-941, the Illinois Withholding Income Tax Return, once per quarter. Due dates are the last day of the month after the quarter closes: April 30, July 31, October 31, and January 31.⁶ The return reports total tax withheld for the quarter and reconciles it against your IL-501 deposits. You can file through MyTax Illinois.

If you discover an error on a return already filed, correct it by filing Form IL-941-X for the affected period.⁷

Year-End W-2s Must Be Filed Electronically

Your fourth-quarter IL-941 doubles as your annual reconciliation, including a line reporting the total number of W-2s issued for the year.⁷ Illinois requires all employers to submit W-2 forms electronically. IDOR does not accept paper W-2 submissions, and there is no small-employer exception; even a single W-2 must be filed electronically.⁸

New-Hire Reporting Within 20 Days

Within 20 days of an employee’s first day, report the hire to the Illinois New Hire Directory. The report includes the employee’s name, home address, Social Security number, and date of hire, along with your business name, address, and federal employer identification number.⁹ You can optionally list a separate address for income-withholding orders. The data feeds child-support enforcement and fraud prevention systems.

Employees Who Live in Iowa, Kentucky, Michigan, or Wisconsin

Illinois has reciprocal income tax agreements with those four states.¹⁰ If an employee lives in one of them but works for you in Illinois, you do not withhold Illinois income tax. The employee must give you the appropriate exemption certificate from their home state, and you withhold for that state on request. The reverse works the same way for Illinois residents working across the border. Local taxes in those states are not covered by the reciprocity agreements and may still apply.

Contractors Are Not Employees, but Prove It

Withholding applies only to employees. Illinois uses an ABC test that presumes a worker is an employee unless the employer proves all three of these:

The worker is free from the employer’s control and direction, both under contract and in practice.
The work is outside the employer’s usual business, or performed outside all of the employer’s business locations.
The worker is engaged in an independently established trade, occupation, or business.¹¹

Fail any prong and the worker is an employee for state purposes. Misclassification can trigger back withholding, unemployment contributions with interest, and coordinated audits by IDOR, IDES, and the Illinois Department of Labor.¹¹

Penalties and Interest

Withholding penalties come from the Uniform Penalty and Interest Act and stack quickly.

Late Filing

An initial late-filing penalty is 2% of the tax due, capped at $250. If you still haven’t filed within 30 days after IDOR mails a notice of nonfiling, an additional penalty applies: the greater of $250 or 2% of the tax shown on the return, up to $5,000.¹²

Late Payment

Failing to pay withheld tax by the due date carries a penalty that grows the longer you wait:

Paid within 30 days of the due date: 2% of the unpaid amount.
Paid more than 30 days late but before an IDOR audit: 10%.
Paid after an audit begins: 20%, reduced to 15% if you pay in full within 30 days of receiving audit findings.¹²

Interest

Interest accrues from the original due date until you pay. The rate tracks the federal underpayment rate under Section 6621 of the Internal Revenue Code and adjusts every January 1 and July 1.¹³

Personal Liability

Withholding is a trust tax: money you collected from employees that belongs to the state. Any officer or employee who has control over filing returns and paying the tax, and who willfully fails to do so, is personally liable for the full unpaid amount plus interest and penalties.¹⁴ IDOR can pursue individual assets even after the business closes or files for bankruptcy. The Income Tax Act adds a separate penalty on anyone required to collect and pay over withholding who willfully fails to.¹⁵

Options if You’re Already Behind

Reasonable Cause

Illinois waives late-filing and late-payment penalties if you can show the failure was due to reasonable cause, evaluated case by case under IDOR’s rules.¹⁶ You can raise reasonable cause on a penalty without disputing the underlying tax. The waiver covers penalties under Sections 3-3, 3-4, 3-5, and 3-7.5 of the Act, but not the personal-liability penalty under Section 3-7. Willful failure to pay over trust taxes cannot be excused this way.¹⁷

Voluntary Disclosure

If you discover unfiled or underpaid periods before IDOR contacts you, the Voluntary Disclosure Program waives all penalties associated with the disclosed liability, provided you pay all tax and interest within 60 days of being billed.¹⁸ It also limits the look-back to four years from each unfiled return’s original due date.¹⁹

Two limits matter. If you actually collected withholding from employees but never remitted it, you must pay it back for all periods, not just the last four years, and failure to remit previously collected tax disqualifies you from the program. And once an audit notice arrives, the door closes.

Closing a Withholding Account

When you stop employing workers in Illinois or shut the business down, close the withholding account rather than simply stop filing. You can enter a cease date through MyTax Illinois.²⁰ File a final IL-941 covering the last period you paid wages, and submit W-2s electronically for that year. Leaving an account open after wages stop generates nonfiling notices and avoidable penalty assessments. IDOR’s Central Registration Division can help at 217-785-3707.

1
Illinois Department of Revenue. 2026 Booklet IL-700-T Illinois Withholding Tax Tables
2
Illinois Department of Revenue. Withholding Income Tax
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Illinois Department of Revenue. FY 2026-15 What’s New for Illinois Income Taxes
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Illinois Department of Revenue. REG-1 Illinois Business Registration Application
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Illinois Department of Revenue. Form IL-W-4 Employee’s Illinois Withholding Allowance Certificate and Instructions
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Illinois Department of Revenue. Publication 131 – Withholding Income Tax Payment and Filing Requirements
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Illinois Department of Revenue. IL-941-X Instructions – Amended Illinois Withholding Income Tax Return
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Illinois Department of Revenue. Electronic W-2 and 1099 Transmittal Programs
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Illinois Department of Employment Security. New Hire Reporting
10
Legal Information Institute. Illinois Administrative Code Title 86 Section 100.7090 – Reciprocal Agreement
11
Illinois Department of Employment Security. Employee Misclassification
12
Justia. Illinois Code 35 ILCS 735 – Uniform Penalty and Interest Act
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Illinois General Assembly. Illinois Code 35 ILCS 735/3-2 – Interest
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Illinois General Assembly. Illinois Code 35 ILCS 735/3-7 – Personal Liability for Officers and Employees
15
Illinois General Assembly. Illinois Code 35 ILCS 5/1002 – Failure to Pay Tax
16
FindLaw. Illinois Code 35 ILCS 735/3-8 – Reasonable Cause
17
Legal Information Institute. Illinois Administrative Code Title 86 Section 700.400 – Reasonable Cause
18
Illinois Department of Revenue. Voluntary Disclosure Program
19
Legal Information Institute. Illinois Administrative Code Title 86 Section 210.126 – Voluntary Disclosure
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Illinois Department of Revenue. Instructions for Form CBS-1 Notice of Sale Purchase or Transfer of Business Assets