How to Complete and File the Illinois REG-1 Business Registration Application

Illinois REG-1 business registration is how you set up your state tax accounts with the Illinois Department of Revenue (IDOR) before you sell, buy, or hire in Illinois. You can file Form REG-1 online through MyTax Illinois at mytax.illinois.gov, which processes in about one to two business days, or send a paper form to IDOR’s Springfield office, which takes six to eight weeks.¹ There is no filing fee for the REG-1 itself, though a few license types require a surety bond before IDOR will complete your registration.

Who Has to File Form REG-1

You must register with IDOR if you conduct business in Illinois or with Illinois customers. That covers sole proprietors, partnerships, corporations, LLCs, exempt organizations, and government agencies that withhold Illinois income tax from employees’ paychecks.¹ Under the Retailers’ Occupation Tax Act, it is unlawful to sell tangible personal property at retail in Illinois without a certificate of registration from the Department, and as of January 1, 2025, that requirement also covers leasing tangible personal property.²

Service providers who transfer goods as part of their work, businesses with employees subject to Illinois income tax withholding, and companies dealing in regulated products like liquor, cigarettes, tobacco, motor fuel, or medical cannabis all register through the REG-1.¹

Out-of-state sellers cross into Illinois registration territory once they hit the economic nexus threshold. Effective January 1, 2026, the sole threshold is $100,000 or more in cumulative gross receipts from sales to Illinois purchasers during the preceding 12-month lookback period. The prior 200-transaction threshold no longer applies, and remote retailers who previously met only the transaction count will be moved by IDOR to “voluntary use tax” status.³ A marketplace facilitator that also makes its own sales needs two separate sales and use tax accounts, one for direct sales and one for sales made on behalf of marketplace sellers.⁴

One boundary worth flagging: federal 501(c)(3) status does not give you an Illinois sales tax exemption. To get an “E-number” for tax-exempt purchases, you file Form STAX-1 separately, not the REG-1. That said, if your exempt organization has Illinois employees, you still file a REG-1 to set up the withholding account.⁵

When to File

The rule is straightforward: register before you start. IDOR requires you to complete registration before making any purchases, sales, or hiring an employee.¹ Do the math on processing time. Online filers can be operational within a couple of business days; anyone mailing a paper form needs to build in a six-to-eight-week runway before opening day.

What to Gather Before You Start

Have everything below in front of you before opening the form or the portal. A missing item will stall the application.

Federal Employer Identification Number (FEIN) issued by the IRS. Sole proprietors without one can use the Social Security number they file taxes under.
Legal business name as filed with the Illinois Secretary of State, plus any “doing business as” name you use.
Owner, officer, and partner details: full name, title, home address (no P.O. boxes), date of birth, phone number, and Social Security number for each. Which people you list depends on entity type: a corporation lists its president, secretary, and treasurer; an LLC lists managers and members; a partnership lists general partners. Overflow goes on Schedule REG-1-O.
The exact date you began or will begin operating in Illinois.
Every physical business location. Multiple locations go on Schedule REG-1-L.
The tax types that apply to your activities, including retailers’ occupation tax, withholding income tax, tire user fee, Chicago soft drink tax, hotel operators’ tax, and others.

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If you will have Illinois employees, you also complete Schedule REG-UI-1 with the REG-1. IDOR handles state income tax withholding, but unemployment insurance registration is separate and goes through the Illinois Department of Employment Security at ides.illinois.gov.⁷

Supplemental Schedules

The REG-1 is modular. The base form captures general business information; supplemental schedules cover specialized tax types. Attach only the ones that fit your business:

Schedule REG-1-A: Liquor warehousing
Schedule REG-1-C: Cigarettes and tobacco products
Schedule REG-1-D: Electricity purchased for non-residential use
Schedule REG-1-G: Natural gas purchased from outside Illinois for your own use
Schedule REG-1-L: Additional business locations in Illinois
Schedule REG-1-MC: Medical cannabis
Schedule REG-1-MKP: Marketplace facilitator
Schedule REG-1-O: Additional owners, officers, or partners
Schedule REG-1-R: Responsible party information if someone other than the applicant will file returns and pay taxes
Schedule REG-1-T: Telecommunications
Schedule REG-UI-1: Illinois employees (withholding)
Form REG-8-A: Motor fuel and aviation fuel

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How to Submit the REG-1

Online Through MyTax Illinois

The fastest route is electronic filing at mytax.illinois.gov. From the homepage, click “Register a New Business (Form REG-1)” and follow the prompts. The system walks you through each step, lets you select the tax types and schedules that apply, and finishes with a digital signature. Processing takes roughly one to two business days.¹

Paper Application

Download the current REG-1 from tax.illinois.gov/forms/reg/reg-1.html, complete and sign it, and submit by one of the following methods:⁸

Mail: Central Registration Division, Illinois Department of Revenue, PO Box 19030, Springfield, IL 62794-9030
Fax: 217-785-6013
Email: REV.CentReg@Illinois.gov

A responsible party, such as the owner, a corporate officer, or an authorized member, must sign the form, certifying the information is true and correct. Paper applications take six to eight weeks to process.¹

Bond Requirement for Certain Licenses

If you are registering as a cigarette distributor, cigarette machine operator, direct wine shipper, motor fuel distributor, motor fuel receiver, liquor distributor, or tobacco products distributor, IDOR may require a surety bond (Form REG-4-A) or an irrevocable letter of credit (Form REG-4-D) before issuing your certificate. You are not legally registered until IDOR receives that bond. Email rev.regbond@illinois.gov to find out whether one applies. Tobacco products distributors filing their first application, or those with less than $50,000 in tax liability in the preceding year, are exempt from the bond requirement.⁹

What You Receive After Registration

Once IDOR processes your application, you receive a Certificate of Registration or License along with your Illinois taxpayer ID number. The certificate identifies which taxes you are responsible for and shows your Illinois Account ID or license number.¹⁰ Illinois law requires you to display it conspicuously at your principal place of business.²

Something that catches new registrants off guard: IDOR no longer prints and mails certificates for certain tax types, including Retailers’ Occupation Tax.¹ For those, you access the certificate through your MyTax Illinois account. Even if you filed on paper, you will need to create a MyTax Illinois account to print it.

From that point forward you file returns on the schedule IDOR assigns, whether monthly, quarterly, or annually, based on your tax types and activity. You also become responsible for collecting and remitting the applicable taxes, which for retailers means charging the correct state and local sales tax rate based on the location of the sale.

What Happens If You Don’t Register

Selling tangible personal property at retail in Illinois without a certificate of registration is unlawful.² Beyond that, unpaid tax liabilities pile up with penalties and interest under the Uniform Penalty and Interest Act, and corporate officers or LLC members with control over tax filings can be held personally liable for unpaid trust taxes when the failure was willful.¹¹ The names and Social Security numbers you list on the REG-1 are the same people IDOR looks at when a business fails to pay.

Updating or Closing Your Registration

If your address changes, you add a location, ownership shifts, or you take on a new tax responsibility, update the registration through MyTax Illinois, by calling IDOR at 217-785-3707, or by visiting an IDOR office. Skipping updates can cause returns and payments to be processed incorrectly, trigger erroneous tax bills, or block important notices from reaching you.¹

When you stop doing business in Illinois, contact IDOR through MyTax Illinois, by phone, or in person, and check the “final return” box on your final return for each tax type. Some return types don’t have that checkbox, and for those you contact IDOR directly to close the account.¹²

1
Illinois Department of Revenue. Business Registration
2
Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 120/2a – Registration of Retailers
3
Illinois Department of Revenue. FY 2026-12, Destination-Based Retailers’ Occupation Tax Changes
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Illinois Department of Revenue. Frequently Asked Questions (FAQs) for Marketplace Facilitators, Marketplace Sellers, and Remote Retailers
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Illinois Department of Revenue. Information for Exclusively Charitable, Religious, or Educational Organizations; Governmental Bodies; and Certain Other Tax-Exempt Organizations
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Illinois Department of Revenue. REG-1 Illinois Business Registration Application
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Illinois Department of Revenue. Business Registration Forms
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Illinois Department of Revenue. Registering Your Business
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Illinois Department of Revenue. REG-4-A, Financial Responsibility Bond Instructions
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Illinois Department of Revenue. What Is the Difference Between a Certificate of Registration, License, Certificate of Resale, and Tax-Exempt Number?
11
Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 735 – Uniform Penalty and Interest Act
12
Illinois Department of Revenue. Closing Your Business