Getting a tax ID number in Illinois takes two steps. First, apply to the IRS for a federal Employer Identification Number, which is free and issued immediately through the online application. Then register with the Illinois Department of Revenue using Form REG-1, most easily submitted through the MyTax Illinois portal. Not every business needs both, so the first question is which numbers actually apply to you.
Do You Need a Federal EIN
An EIN is the nine-digit number the IRS uses to identify a business. You need one if you have employees or plan to hire them, operate as a partnership, corporation, LLC, or nonprofit, file employment or excise taxes, withhold taxes on income paid to a non-resident alien, or manage a trust, estate, retirement plan, or IRA.
Sole proprietors with no employees are the exception. Illinois lets you use your Social Security Number for both federal and state tax purposes in that situation.1Illinois Department of Revenue. Your Application Asks for a FEIN – How Do I Know If I Need a FEIN? Many sole proprietors still get an EIN anyway, because it keeps their SSN off W-9s and 1099s and because most banks want one before opening a business account.2U.S. Small Business Administration. Open a Business Bank Account
Applying for the Federal EIN
The IRS online application produces an EIN immediately on approval, and there is no fee.3Internal Revenue Service. Get an Employer Identification Number Go directly to irs.gov; the IRS warns against paid third-party sites that offer the same thing.
Have these ready before you start:
- Social Security Number or ITIN of the “responsible party,” the person who controls the entity.
- Legal business name as it appears on any documents filed with the Illinois Secretary of State.
- Entity type: sole proprietorship, partnership, LLC, corporation, nonprofit, trust, or estate.
- Business address and the reason you are applying.
The online tool runs Monday through Friday from 6:00 a.m. to 1:00 a.m. the next day, Saturday from 6:00 a.m. to 9:00 p.m., and Sunday from 6:00 p.m. to midnight, Eastern time. You have to finish in one sitting. The session cannot be saved and times out after 15 minutes of inactivity. Print the confirmation notice when you finish; that letter is your proof of the EIN until the formal notice arrives in the mail.
Once assigned, your EIN stays with the business permanently unless a structural change forces a new one.
If You Do Not Have an SSN or ITIN
The online application requires the responsible party to have an SSN or ITIN. Foreign owners without either need to apply another way.4Internal Revenue Service. Employer Identification Number
- Phone: 267-941-1099 (not toll-free), Monday through Friday, 6:00 a.m. to 11:00 p.m. Eastern.
- Fax: submit a completed Form SS-4 to 855-215-1627 (U.S.) or 304-707-9471 (outside the U.S.).
- Mail: Internal Revenue Service, Attn: EIN International Operation, Cincinnati, OH 45999.
Phone applications usually produce an EIN during the call. Fax takes about four business days. Mail can take four to six weeks, so start early if you need the number before you can register with Illinois.
Registering With the Illinois Department of Revenue
With the EIN in hand, register the business with the Illinois Department of Revenue on Form REG-1, the Illinois Business Registration Application. Illinois law makes it illegal to sell tangible goods at retail without a certificate of registration from IDOR.5Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 120/2a – Registration of Retailers You also need to register if you hire employees, withhold state income tax, or collect any state tax.
The fastest route is the MyTax Illinois portal at mytax.illinois.gov, where you can complete and submit the REG-1 electronically.6Illinois Department of Revenue. MyTax Illinois Help – What Is MyTax Illinois and How Do I Access It? A paper version can be mailed to the Department in Springfield, but processing is slower.
The form collects your federal EIN (or SSN if you are a sole proprietor), legal business name, entity type, and Illinois Secretary of State identification number, plus your physical and mailing addresses. It asks for owner and officer information, which for each person includes name, title, home address, date of birth, ownership percentage, and Social Security Number. It also asks what your business actually does, when Illinois activity begins, your NAICS code, and which taxes apply to you — sales, use, withholding, hotel, utility, and others.7Illinois Department of Revenue. REG-1 Illinois Business Registration Application The tax selections drive which returns you will file each quarter, so read them carefully.
Online submissions are typically processed within a few business days. Mailed forms take several weeks. Once approved, IDOR issues a Certificate of Registration that must be displayed at your principal place of business. Additional locations get sub-certificates that must be posted at each site.8FindLaw. Illinois Compiled Statutes 35 ILCS 105/6
Unemployment Insurance With IDES
The IDOR registration does not cover unemployment insurance. If you hire employees, you have to register separately with the Illinois Department of Employment Security within 30 days of starting your business.9Illinois Department of Employment Security. Are You a New Employer? That registration is form REG-UI-1.
The REG-1 itself asks whether you will have Illinois employees. If you check yes, it prompts you to complete Schedule REG-UI-1 as part of the same submission,7Illinois Department of Revenue. REG-1 Illinois Business Registration Application so both registrations can be handled in one pass through MyTax Illinois.
Cost
The federal EIN is free. The IRS charges no fee, and paid services offering to get one for you are not the IRS.3Internal Revenue Service. Get an Employer Identification Number The Illinois REG-1 registration is also free to submit.
Penalties for Operating Without Registration
Selling tangible goods at retail in Illinois without a certificate of registration is illegal.5Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 120/2a – Registration of Retailers The Department of Revenue can go to court for an injunction forcing you to stop until you register. Operating after your certificate has been revoked is a Class A misdemeanor, and each day counts as a separate offense. You will also owe penalties and interest on any tax you should have been collecting during the unregistered period.
IDOR can also deny a certificate. Grounds include unpaid taxes from a prior business, a previously revoked certificate, or an incomplete application. If denied, you cannot legally operate until you fix the issue and reapply.
When a Structural Change Forces a New EIN
Your EIN does not expire, but certain changes require a new one.10Internal Revenue Service. When to Get a New EIN
- Sole proprietors: incorporating, forming a partnership, or filing for bankruptcy.
- Corporations: receiving a new charter, merging into a new corporation, or converting to a partnership or sole proprietorship.
- Partnerships: incorporating, dissolving and forming a new partnership, or a single partner taking over as a sole proprietor. A change in partners alone does not require a new EIN as long as the partnership continues.
- LLCs: terminating and forming a new entity, or a single-member LLC beginning to file employment or excise taxes.
When you get a new EIN, update your Illinois registration too. You can register the new entity and close out the old account through MyTax Illinois. Skipping that step is a common compliance mistake and creates confusion about who owes what when returns come due.