How to Get an EIN in Illinois (2026)

Fact-checked by the LegalGlass editorial team against primary sources · Published Aug 6, 2026 · Last updated Aug 6, 2026

An EIN (Employer Identification Number) is a nine-digit federal tax ID issued free by the IRS - Illinois does not issue its own. You apply directly with the IRS: the online application is free and gives you the number immediately, or you can file Form SS-4 by fax or mail. After you have the EIN, you register separately with the Illinois Department of Revenue for state tax accounts.

Quick Answer

What it is
Federal Employer Identification Number (EIN / FEIN) from the IRS
Cost
Free - the IRS never charges for an EIN
Fastest method
Online IRS application; number issued immediately
Form
Form SS-4 (used for fax, mail, and international applicants)
Illinois step
Register with the Illinois Department of Revenue via MyTax Illinois
Who needs one
Employers, corporations, partnerships, and most multi-member LLCs

What Is an EIN and Who Needs One?

An Employer Identification Number is the business equivalent of a Social Security number: a unique nine-digit number the IRS uses to identify a business for federal tax purposes. It appears on payroll filings, business tax returns, and many bank and licensing applications. It is issued by the federal government, so there is no separate Illinois EIN - the same number is used nationwide.

You are required to have an EIN if your business has employees, operates as a corporation or partnership, files employment or excise tax returns, or is a multi-member LLC. A single-member LLC with no employees can technically use the owner's Social Security number, but obtaining an EIN is still recommended to separate personal and business identity.

Even a sole proprietor with no employees often gets an EIN to open a business bank account, hire contractors, or avoid sharing an SSN. Because the EIN is free and permanent, most Illinois businesses simply obtain one at startup. The IRS "Do You Need an EIN?" checklist confirms whether your situation requires one.

Applying Online: The Fastest Method

The IRS online EIN application is the quickest route and is free. It is available to businesses whose principal location is in the U.S. and whose responsible party has a valid Social Security number or ITIN. You complete the interview-style application in one session - it cannot be saved - and receive your EIN immediately upon completion, with a confirmation letter (CP 575) you can download.

The online tool operates only during posted hours (generally Monday through Friday, daytime Eastern time), and the IRS limits issuance to one EIN per responsible party per day. The "responsible party" is the individual who ultimately owns or controls the business; the IRS requires a natural person, not another entity, in that role for most applicants.

Have your formation details ready: legal name, trade name (DBA) if any, mailing address, responsible party name and SSN/ITIN, entity type, and the reason for applying. Finish in one sitting, then save the confirmation letter - banks and the Illinois Department of Revenue will ask for it.

Applying by Form SS-4 (Fax, Mail, or Phone)

If you cannot use the online tool - for example, the responsible party has no SSN or ITIN - you apply using Form SS-4, Application for Employer Identification Number. The form captures the same information as the online interview. International applicants without a U.S. taxpayer ID can also apply by phone using the dedicated IRS international line.

Processing time depends on the method. Fax applications are typically processed in about four business days, with the EIN faxed back if you provide a return fax number. Mailed applications generally take about four weeks. Choose fax when you need the number quickly but cannot apply online.

Complete Form SS-4 carefully; errors delay processing. Keep a copy for your records. Whichever method you use, the EIN itself is always free - ignore third-party sites that charge a fee to "obtain" an EIN, since they are simply reselling a free government service. Apply directly through the IRS.

After Your EIN: Registering With Illinois

The EIN handles your federal identity. To operate in Illinois you generally must also register with the Illinois Department of Revenue (IDOR). Most businesses register through MyTax Illinois (or Form REG-1) to obtain an Illinois Business Tax number and set up accounts for sales tax, use tax, and employer withholding as applicable.

If you sell tangible goods, you register to collect Illinois Retailers' Occupation (sales) Tax. If you have employees, you register for Illinois income tax withholding and, separately, for unemployment insurance with the Illinois Department of Employment Security. Your EIN is the federal identifier that ties these state accounts together.

If you formed an LLC or corporation, you also registered the entity with the Illinois Secretary of State - a different step from both the EIN and IDOR registration. See Illinois LLC tax filing and the business tax hub for how these accounts fit together.

Common EIN Mistakes to Avoid

A few errors recur. First, paying a third party for an EIN: the IRS issues it for free, and paid "filing services" add no value to the number itself. Second, applying for multiple EINs when you do not need them - a single business generally keeps one EIN for its life, though you may need a new one if you change entity type (for example, incorporating a sole proprietorship).

Third, naming the wrong responsible party. The IRS expects the true principal owner or controller, and you should update the IRS (using Form 8822-B) if that person changes. Fourth, losing the CP 575 confirmation letter; keep it, because reissuing proof of your EIN later (a 147C letter) takes time.

Finally, confusing the EIN with state registrations. An EIN alone does not register you for Illinois sales tax, withholding, or your local licenses. Treat the EIN as the first step, then complete IDOR registration and any Illinois licenses your activity requires.

Using and Protecting Your EIN

Once issued, your EIN is permanent - it is not reused or reassigned, even if you never file with it. Use it consistently on federal returns, payroll, information returns (like 1099s you issue), and bank paperwork. Keep it as carefully as an SSN, since it can be used in identity theft against your business.

You generally keep the same EIN for the life of the business. You need a new EIN mainly when the entity itself changes - for instance, a sole proprietor incorporates, a partnership converts to a corporation, or ownership structure changes in ways the IRS specifies. Simply changing your business name or address does not require a new EIN; you update the IRS instead.

If you close the business, you can ask the IRS to close the business account associated with the EIN, though the number is never truly canceled. With your EIN in hand and your Illinois registrations complete, you are set up to file federal and state taxes correctly. See how to get an EIN for the national overview.

Frequently Asked Questions

Is there a separate Illinois EIN?

No. The EIN is a federal number issued by the IRS and used nationwide. Illinois does not issue its own EIN. After getting your federal EIN you register separately with the Illinois Department of Revenue for state tax accounts.

How much does an EIN cost in Illinois?

Nothing. The IRS issues EINs for free through its online application, or by fax or mail using Form SS-4. Avoid third-party websites that charge a fee to obtain what is a free government service.

How long does it take to get an EIN?

The online IRS application issues the EIN immediately. Fax applications using Form SS-4 typically take about four business days, and mailed applications about four weeks. Online is the fastest option for eligible applicants.

Do I need an EIN for an Illinois sole proprietorship?

Not always. A sole proprietor with no employees may use a Social Security number, but many get an EIN to open a business bank account and keep the SSN private. An EIN is required once you hire employees.

What do I do after getting my EIN in Illinois?

Register with the Illinois Department of Revenue through MyTax Illinois for sales tax and withholding as needed, register for unemployment insurance if you have employees, and confirm any local business licenses your activity requires.

Related

More Illinois business guides

Business License In Form An Llc In Annual Report Articles Of Organization Business Entity Search Certificate Of Formation Dba Filing Llc Tax Filing Operating Agreement Registered Agent

Sources

  1. IRS - Apply for an EIN Online (free; immediate).
  2. IRS - How to Apply for an EIN (online, fax, mail, phone).
  3. IRS - About Form SS-4.
  4. IRS - Do You Need an EIN?
  5. IRS - Responsible Parties and Nominees.
  6. IRS - Change of Address or Responsible Party (Form 8822-B).
  7. Illinois Department of Revenue - Home (register a business; MyTax Illinois).
  8. Illinois Department of Revenue - MyTax Illinois (state tax registration).
  9. Illinois Secretary of State - Business Services.
  10. Illinois Department of Employment Security - Employer Resources (unemployment insurance).
  11. IRS - Single Member LLCs.
  12. IRS - Employer ID Numbers.
  13. Cornell Law School Legal Information Institute - Employer Identification Number.
  14. U.S. Small Business Administration - Get Federal and State Tax ID Numbers.

LegalGlass provides general information for educational purposes and is not a law firm or a substitute for advice from a licensed attorney or tax professional. Laws, fees, and thresholds change; verify current requirements with the IRS and the Illinois Department of Revenue before acting.