Overview: When starting a business with employees in Illinois, you must register for State Income Tax Withholding with the Department of Revenue (IDOR) and Unemployment Insurance (UI) Tax with the Department of Employment Security (IDES). Both registrations can be completed in a single application through the MyTax Illinois portal.
Important! This guide does not constitute legal or tax advice. You can consult a CPA or attorney for official guidance.
Taxes You Must Register For:
Registration Process
Registration Steps
A. Create a MyTax Illinois Account
Go to MyTax Illinois
Click “Register a New Business (Form REG-1)”
Enter your FEIN and complete the business details
Submit the registration form online
Processing Time: Typically 1–2 business days
B. Select Applicable Tax Types
During registration, be sure to select:
State Income Tax Withholding
Unemployment Insurance (UI) Tax
This ensures both your Taxpayer ID (IDOR) and Unemployment Account Number (IDES) are assigned through a single application.
C. Activate Your Online Account
After submission, you’ll receive a confirmation screen and an authentication code by email
Use this code to activate your MyTax Illinois user account
All tax types under your FEIN or SSN will be linked to your MyTax Illinois profile
Alternative Registration Methods (Optional)
If not registering online, you may register:
By Mail
Submit Form REG-1 to IDOR
Submit Form UI-1 to IDES
In Person
Visit a local Illinois Department of Revenue office
Processing Time for Paper Forms: 4–6 weeks
Grant Third-Party Access to Check
To authorize filing on your behalf:
Log in to MyTax Illinois
Navigate to Settings → Manage Third Party Access
Set the following:
Allow = Yes
Default Access = Third Party
Default Account Access = Full Access
Contact Information
IDOR (Withholding): (217) 785-3707 or [email protected]
IDES (UI Tax): (800) 247-4984
Additional Resources: IDES Employer Resources