Illinois payroll tax and registration guide

Updated September 7, 2023

What we'll cover

• What information OnPay needs from you
• What state and local taxes and filings OnPay handles for Illinois employers
• Where you can find the tax account numbers needed
• Paying employees in other states?

Why is this important?

The following information requests and registration instructions are required before you can use a payroll provider to run payroll. This is in compliance with state payroll tax regulations. Without this information, OnPay is unable to file or deposit any tax payments for your company, and will not be responsible for any resulting penalties or interest. Note: If this isn't the only state where you have employees, there will be a separate guide like this one for each state where you hire and pay workers. 

Let Middesk handle your state tax registrations (and more)

If you'd like help, our partner Middesk makes hiring employees and staying compliant with every state agency simple and easy.

• Register with every state agency to get the tax IDs you need within minutes
• Stay compliant as you grow by managing agency mail and notices in your dashboard
• Manage your government accounts in one place on Middesk's intuitive platform
• Foreign Qualify with the Secretary of State to create payroll tax accounts 

Learn more about Middesk→

What information OnPay needs from you

What state and local taxes and filings OnPay handles for Illinois employers

Where you can find the tax account numbers needed

If you are an existing employer who has previously run payroll in Illinois, you likely already have the IDs and online accounts needed for OnPay to process your tax filings.

If you are a new employer in Illinois, you will need to register your business with the Illinois Department of Revenue and the Illinois Department of Employment Security. This must be completed for OnPay to be able to file and pay your Illinois taxes.

Withholding Tax Account Number

Existing Illinois Employer: 

This account number will include your Federal EIN, and you can find the ID on your Illinois Withholding Income Tax Return (IL-941).

New Illinois Employer: Register with the Illinois Department of Revenue 

• Electronically register through MyTax Illinois (approximately one to two days to process)
• Complete and mail Form REG-1, Illinois Business Registration Application, to the address on the form (Form REG-1 is also available on their website as a fillable form). 
• Registration forms are also available by calling the Department of Revenue at 1-800 356-6302.
• You'll be able to register using your Federal EIN. Your account number will include your Federal EIN.

Unemployment Tax Account Number and contribution rate

Existing Illinois Employer: 

• Your Unemployment account number and your Illinois UI Contribution Rate will be on the Notice of Contribution Rate that you receive from the Illinois Department of Employment Security (IDES) each year.
• Your Unemployment Tax Rate can be found in the far contribution rate box of the Tax Rate Notice. 

New Illinois Employer: Register with the Department of Employment Security

• Register your business with the IL Department of Employment Security.
• You'll instantly be issued an Unemployment Account Number in the format of Example: 1234567-8 or 1234567. It is important to note that your unemployment tax number is NOT the same as your FEIN. The last digit of your Unemployment number is called the check digit and the department will often omit it from correspondence. If you don't receive your Unemployment ID, please call the agency at (800)247-4984 to request it.
• New employers generally have a rate of 3.95% for SUTA with a wage base of $13,271.

Paying employees in other states?

If you operate in multiple states or just have employees working from home across a state line, it's important to file the correct state forms for those workers. See what forms we file in the states where you pay employees.

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