The Illinois Secretary of State keeps every registered corporation, LLC, LP and LLP on a public database, free to search. Most people arrive at it for one of two reasons, and the useful advice is completely different depending on which one you are.
If you are checking out a company — a supplier, a landlord, someone you're about to sign with — you want to read the record properly, and the section on what each field means is the one you want. If you are checking a name before forming an LLC, the search is only half the answer, and the half most guides skip is the part that actually decides it.
Where to search
The official tool is the Illinois Business Entity Search at apps.ilsos.gov. It is free and needs no account, and it covers corporations, not-for-profit corporations, LLCs, limited partnerships and LLPs. Opening a company gives you what Illinois calls a File Detail Report — and from the Secretary of State's business search page you can also buy a Certificate of Good Standing if you need proof rather than a screenshot. Every commercial "Illinois business lookup" site — including the ones outranking the state's own page — is querying or mirroring this same public data, so there is no reason to pay anyone for access to it.
The eight ways Illinois lets you search
Illinois gives you more search methods than most states, and picking the wrong one is why people get empty results. The form asks you to choose a search method first, then enter one term. These are the eight, and what each is actually good for:
| Search method | Use it when |
|---|---|
| Business Name | You know roughly what the company is called and want that specific entity. |
| Partial Word | You're checking whether a name is taken. This is the one to use before forming — it catches the near-matches that a full-name search hides. |
| Keyword | Broader again: finds your distinctive word wherever it sits in a name. Pair it with Partial Word when testing availability. |
| File Number | You already have the state's ID for the entity — the most precise option, since names repeat and change. |
| Registered Agent | Find every company that has designated a particular agent. Useful for checking a commercial agent, or seeing what else sits behind one. |
| President | Find companies where a named person is listed as president (corporations). |
| Secretary | Same, for the secretary role. |
| Manager | The LLC-relevant one: find companies where someone is listed as a manager. |
The practical rule: Business Name is for finding a company; Partial Word and Keyword are for clearing a name. If you search your intended name with Business Name, get nothing, and stop there, you have not actually tested availability — you have tested for an exact twin. Run it again as a Partial Word search on the distinctive part and you will see what the Secretary of State will see.
One note on etiquette and terms: the state says plainly that the database is for individual searches and may not be used to copy or download bulk information. Look things up freely; don't scrape it.
Checking a name: the rule that actually decides it
Here is the trap. People search the exact name they want, see no match, and assume they're clear. Illinois does not work that way. Under the Illinois Limited Liability Company Act, a new LLC name must be distinguishable upon the records of the Secretary of State — not merely "not identical" — and the Secretary of State is the one who decides whether it is.
Two things follow from the statute, and both cost people filing fees when they get it wrong:
| The rule (805 ILCS 180/1-10) | What it means when you search |
|---|---|
| The name must contain "limited liability company", "L.L.C." or "LLC" — or "L3C" for a low-profit LLC | Search the distinctive part of the name on its own. The designator is required on every LLC, so it can never be the thing that makes yours different. |
| The name must be distinguishable from existing LLCs, admitted foreign LLCs, reserved names, registered assumed names, and corporate names | Your competition is wider than the LLC list — a corporation or a registered assumed name can block you just as effectively. |
| A name is not distinguishable merely because it differs by the words "limited", "liability" or "company", their abbreviations, articles, conjunctions, contractions, or a different tense or number of the same word | "The Oak Table LLC" will not clear past "Oak Tables, L.L.C." Changing the, and, or singular-to-plural changes nothing in the state's eyes. |
So search broadly rather than precisely: take the distinctive word out of your name, search that alone, and look at everything similar that comes back — including corporations, not just LLCs. If something close exists, assume it blocks you until the Secretary of State says otherwise.
Reading a company's record
If you are researching an existing business rather than naming a new one, these are the fields worth actually reading:
| Field | What it tells you |
|---|---|
| Status | Whether the entity is in good standing. Illinois issues a certificate of dissolution roughly 120 days after a delinquency notice, so a company that quietly stopped filing eventually shows up here as dissolved. |
| File number | The state's own ID for the entity. Names change and repeat; this doesn't. |
| Registered agent and registered office | The person or company that accepts legal papers, at a physical Illinois street address. See below — this is the most misread line on the record. |
| Principal place of business | Where the company actually operates, often a different address entirely. |
| Manager / member listed | Illinois LLC filings do not publish a full ownership list, so do not read the name here as "the owner". |
What the registered agent line actually means
This is the part every competing search page leaves out, and it is the one with consequences. Under 805 ILCS 180/1-35, every Illinois LLC must continuously maintain a registered agent and a registered office in the state — and an individual serving as agent must be an Illinois resident with a physical Illinois street address. A PO box on its own is not acceptable for the registered office.
What that means in practice: the address on that line is where a lawsuit against the company is legally delivered. Service there counts whether or not anyone forwards it. That is how a business ends up with a default judgment over a case it never saw — an agent who moved, a friend who agreed years ago and has since stopped opening the mail, or a service that lapsed when a card expired.
It is worth looking up your own company once a year for exactly this reason. If the agent shown is wrong, Illinois fixes it with a Statement of Change of Registered Agent and/or Registered Office (Form LLC-1.36/1.37) for $25, filed by mail or online — with 24-hour expedited service available for an extra $50. Our change-of-agent guide covers the order to do it in so you are never left without an agent on record.
The Illinois numbers behind the search
If the name is clear and you're about to file, these are the figures to plan around — all of them verified against the state's own sources:
| What | Cost | Timing |
|---|---|---|
| Articles of Organization | $150 | One-off, at formation |
| Annual report | $75 | Due in the 60 days before the first day of your anniversary month |
| Missed annual report | $100 penalty | Plus $100 for each further delinquent year; dissolution follows about 120 days after the notice |
| Change of registered agent | $25 | Form LLC-1.36/1.37, any time (+$50 for 24-hour expediting) |
| Series LLC (if you need one) | $400 to form | Plus $50 per Certificate of Designation and $50 per active series on the annual report |
Note the annual report timing, because it is the single most missed thing in Illinois: there is no statewide due date. Your deadline is tied to the month you formed, which means it is different from every other business you know and nothing will remind you of it. Every state's deadline is in our annual report deadline calendar, with a downloadable reminder.
The Illinois cost nobody's search page mentions
One more thing that belongs in any honest Illinois guide. Even a plain pass-through LLC owes the Personal Property Replacement Tax — an entity-level Illinois tax of 1.5% on the LLC's net income, paid by the business on Form IL-1065 or IL-1120-ST, on top of the 4.95% personal income tax the owner already pays on the same profits. An LLC taxed as a C-corp pays 2.5% instead.
It will not affect your name search, but it will affect whether Illinois is where you want the company. Most "start an LLC in Illinois" pages never mention it. The full picture is in our Illinois registered agent and LLC guide, and you can compare Illinois against every other state in the LLC cost calculator.
Being in the database is not the same as being licensed
A common mix-up, and worth knowing before you rely on what you found. The Secretary of State's database tells you an entity is registered — that it exists, who its agent is, and whether it is in good standing on its filings. It says nothing about whether the business holds the licence it needs to do its work. Contractors, salons, brokers, health practitioners and dozens of other trades are licensed by the Illinois Department of Financial and Professional Regulation, not by the Secretary of State, and a company can sit in perfect standing here while holding no professional licence at all. If you are vetting a tradesperson, check both.
One thing to decide before you file
Whatever name you settle on, the registered agent address you put on the Articles of Organization goes onto the same public database you have just been searching — permanently, and findable by anyone running the search you just ran. If you are an Illinois resident with a street address you're happy to publish, being your own agent is free and perfectly sensible; our guide to acting as your own agent sets out when that works. If you'd rather not have your home address turn up in someone else's due diligence, that is what a commercial agent is for.