The official search
The registry is run by the Illinois Secretary of State, Department of Business Services (Corporation/LLC Division).
- Search page: https://apps.ilsos.gov/businessentitysearch
- Cost: Free
- Login: None required
The database covers corporations, not-for-profit corporations, LLCs, limited partnerships, and LLPs registered with the Secretary of State, plus assumed names (DBAs) filed by those entities. Sole proprietorships and general partnerships do not appear — they register at the county level.
There is no separate "name availability" tool that gives a yes or no. You judge availability from the search results, and the Department of Business Services makes the final distinguishability decision when your filing or name reservation is reviewed. The database is licensed for individual lookups only; the Secretary of State prohibits copying or scraping it.
A results list shows the file number, entity type, name, status, registered effective date, and registered agent. A detail record adds the legal name (and assumed name, if any), principal address, jurisdiction, date of organization, duration, annual report information, registered office address, and filing history. Member and manager names are not displayed as an ownership roster on the public record.
Step by step
- Open the Business Entity Search and pick one search method. Illinois offers eight: Business Name, Keyword, Partial Word, File Number, Registered Agent, President, Secretary, and Manager.
- Start with Business Name, entering your name without "LLC." This works like a starts-with search on the name as entered.
- Run a Keyword search on the most distinctive word in your name. This finds conflicts where the word appears anywhere in an existing name.
- Run a Partial Word search on a fragment — for example, "Midwest Construct" would find "Midwest Construction Services LLC." This is your best tool for catching near-misses the other modes miss.
- Check every entity type and the assumed names. Because distinguishability is tested against corporate names and registered assumed names too, a conflict can come from any of them, not just LLCs.
- If nothing conflict appears, the name is probably available — but only the Department's review of your actual filing is definitive.
Illinois's name rules
The rules are in 805 ILCS 180/1-10 of the Illinois Limited Liability Company Act.
Designator. The name must contain "Limited Liability Company," "L.L.C.," or "LLC." One exception: a low-profit LLC uses the designator "L3C" instead.
Distinguishable. The name must be distinguishable upon the records of the Secretary of State from:
- Every LLC with articles of organization on file
- Every foreign LLC admitted to transact business in Illinois
- Every reserved name
- Every assumed name registered with the Secretary of State
- Every domestic and foreign corporate name and assumed corporate name
Differences that do not count. Adding "limited," "liability," or "company" (or their abbreviations) does not distinguish a name, and neither do changes to articles, conjunctions, contractions, abbreviations, tense, or number of the same word. The Secretary of State decides what is distinguishable.
Prohibited terms. An Illinois LLC name may not contain "Corporation," "Corp.," "Incorporated," "Inc.," "Ltd.," "Co.," "Limited Partnership," or "L.P." Note that "Co." and "Ltd." are banned here even though many states allow them. Words restricted by other Illinois statutes can be used only if those statutes' conditions are met — "trust," "trustee," or "fiduciary," for example, require compliance with the Corporate Fiduciary Act, and an LLC organized to accept and execute trusts must actually contain the word "trust."
Characters. The name must consist of English letters, Arabic or Roman numerals, or symbols the Secretary of State can reproduce.
Reserving a name. Illinois allows name reservations under §1-15. Check the Department of Business Services for the current reservation fee and term before relying on figures in third-party guides.
What the search can't tell you
- County-level businesses. Sole proprietorships and general partnerships register with the county and never appear in this database — though assumed names filed by state-registered entities do, and they count against you.
- A final verdict. Illinois gives no availability ruling in the search itself. Approval happens when the Department reviews your filing.
- Trademarks and domains. The search says nothing about federal trademark rights or .com availability.
- Who owns a company. Even though you can search by President, Secretary, or Manager, the public record does not publish a full ownership roster for an LLC.
If the name looks available
File Articles of Organization (Form LLC-5.5) with the Department of Business Services, online through the Secretary of State's filing system at apps.ilsos.gov, or by mail or in person.
- Cost: $150. (Illinois also has a series LLC option: $400 under Form LLC-5.25.)
- Processing: Standard online processing is commonly reported at about 10 business days, and 24-hour expedited service is available for an additional $100 — check the Secretary of State's current service options to confirm.
Ongoing: the annual report (Form LLC-50.1).
- Fee: $75 per year (series LLCs pay $75 plus $50 per series).
- Due date — read this carefully: the report is due before the first day of your anniversary month (the month your Articles were accepted). Form in March, and your report is due by the end of February, not March 31. The deadline is earlier than it sounds.
- Late penalty: $100 if the report is still unfiled roughly 60 days after the anniversary month begins, plus another $100 for each additional year of delinquency — the penalty stacks by year, unlike most states' flat fee.
- Continued delinquency leads to administrative dissolution; reinstatement costs $200.
FAQ
Is the Illinois LLC name search free? Yes. The Business Entity Search is free and requires no login.
What is the difference between Keyword and Partial Word search? Keyword finds a full word appearing anywhere in a name. Partial Word finds a fragment of a word, so "Midwest Construct" matches "Midwest Construction Services LLC." Use both when checking for conflicts.
Can an assumed name (DBA) block my Illinois LLC name? Yes. Under 805 ILCS 180/1-10, your name is tested against registered assumed names and corporate names in addition to LLC names.
How much does it cost to form an Illinois LLC? The Articles of Organization (Form LLC-5.5) filing fee is $150. A series LLC costs $400.
When is the Illinois LLC annual report due? Before the first day of your anniversary month — effectively the end of the month before your formation month. The fee is $75, and the late penalty is $100 plus another $100 per additional delinquent year.
Sources
- Illinois Secretary of State — Business Entity Search: https://apps.ilsos.gov/businessentitysearch
- Illinois Secretary of State — LLC Articles of Organization filing: https://apps.ilsos.gov/llcarticles/status.jsp
- 805 ILCS 180/1-10 (LLC name rules): https://codes.findlaw.com/il/chapter-805-business-organizations/il-st-sect-805-180-1-10/