Illinois LLC Name Rules: How to Name Your Illinois LLC

Filing fee: $150 (online) / $175 (paper)

Processing time: Approximately 10 business days (online); longer for paper

State agency: Illinois Secretary of State, Department of Business Services

Annual report due: Before the first day of the LLC's anniversary month each year

State tax rate: Illinois personal income tax: 4.95% flat rate; Illinois corporate income tax: 9.5%

Illinois LLC naming rules require that your business name include a required designator — either "Limited Liability Company," "LLC," or "L.L.C." — be distinguishable from all other entities on file with the Illinois Secretary of State, and avoid prohibited words that imply a different business structure or a regulated profession.

Illinois LLC naming requirements

Every Illinois LLC name must end with a required designator. You can use "Limited Liability Company" spelled out in full, the abbreviation "LLC," or the punctuated form "L.L.C." — all three are treated as equivalent by the Illinois Secretary of State. If your Articles of Organization don't include one of these, the filing will be rejected.

Beyond the designator, your name must be distinguishable from every other business entity already on file with the Illinois Secretary of State — that includes domestic and foreign LLCs, corporations, limited partnerships, and not-for-profit corporations. "Distinguishable" means more than just different spelling; the name needs to be meaningfully different, not just a variation of an existing name.

One thing that catches people off guard: Illinois does not allow the abbreviations "Ltd." or "Co." as a substitute for the required LLC designator. Those abbreviations are specifically disallowed in Illinois LLC names.

• Name must end with "Limited Liability Company," "LLC," or "L.L.C."
• Name must be distinguishable from all entities on file with the Illinois Secretary of State
• "Ltd." and "Co." are not acceptable LLC designators in Illinois
• Name cannot imply a different business structure (corporation, limited partnership, etc.)

How to check Illinois LLC name availability

Before you file, check whether your proposed name is available using the Illinois Secretary of State's Corporate & Limited Liability Company Name Search database. The search covers corporations, not-for-profit corporations, LLCs, and limited partnerships — so you can spot conflicts across entity types, not just other LLCs.

The Illinois Department of Business Services in the Secretary of State's office reviews every LLC formation filing and can reject names that aren't distinguishable from existing records. Running the search before you file saves you from a rejected Articles of Organization and the delay that comes with it.

Prohibited words and restricted terms

Illinois LLC names can't include terms that suggest a different business structure. Words like "Corporation," "Corp.," "Incorporated," "Inc.," "Limited Partnership," or "LP" are off-limits — they imply your business is something other than an LLC.

Illinois also restricts words that suggest a licensed or regulated profession — things like "Bank," "Insurance," "Attorney," or similar terms — unless your business is legally authorized to use them. This restriction applies to variations and derivatives of prohibited words, not just exact matches.

Symbols and punctuation in your LLC name

Illinois may accept certain special characters in your LLC name at the state level, but the IRS EIN application system only reliably processes letters A through Z, numbers 0 through 9, the ampersand (&), and the hyphen (-). If your legal name includes other symbols, you may have to spell them out or drop them when completing federal EIN paperwork.

Plus, non-standard characters can create mismatched records across state and federal systems. It's worth keeping your name clean — letters, numbers, an ampersand, or a hyphen — so your filings stay consistent across every agency and platform you'll deal with.

Administratively dissolved names

If an Illinois LLC was administratively dissolved — meaning the state dissolved it for non-compliance, not a voluntary closure — its name is off-limits to new businesses for 3 years after the dissolution date. You won't be able to register that name until the 3-year window closes.

There's one exception: if the dissolved LLC gets reinstated within that 3-year period, it reclaims its original name — unless it changes the name during reinstatement. This is worth knowing if you're eyeing a name that shows up in the search results as dissolved.

Trademarks and service marks

Clearing your name with the Illinois Secretary of State only confirms it's available at the state level. It doesn't tell you whether the name infringes on a federally registered trademark or service mark. A name can pass the Illinois name search and still be off-limits if another business holds a federal trademark on it.

Before you commit to a name, search the USPTO's Trademark Electronic Search System (TESS) at the U.S. Patent and Trademark Office website. If you find a potential conflict, talk to a legal professional before filing — rebranding after formation is far more disruptive than catching the issue early.

Illinois assumed name (DBA)

If you want to run your business under a name that's different from your registered LLC name, you can adopt an assumed name — also called a DBA (doing business as) — with the Illinois Secretary of State. This lets you use a customer-facing name without forming a separate legal entity.

To adopt an assumed name, file Form LLC 1.20 — Application to Adopt, Change, or Cancel an Assumed Name — with the Illinois Secretary of State, or use the online assumed name portal at apps.ilsos.gov. The application needs your LLC's legal name, state of organization, whether it's a series LLC, and the assumed name you want to use. The right to use the assumed name takes effect on the date the Secretary of State processes the filing.

How to reserve an Illinois LLC name

If you've found a name you want but aren't ready to file your Articles of Organization yet, you can reserve it with the Illinois Secretary of State by submitting Form LLC-1.15 — Application to Reserve a Name. A reservation holds the name exclusively for 90 days.

Name reservation is optional. If you're ready to form your LLC now, you can go straight to filing Articles of Organization without reserving first. The reservation is useful when you need time to get other things in order — financing, a co-founder agreement, or a lease — before you're ready to file.