Use the Illinois Secretary of State’s free Business Entity Search to check whether a corporation or LLC name is already on record. Search the distinctive part of your name, then compare the results against Illinois’s naming rules, which are stricter than many states’ for LLCs.
If the name is open and you aren’t ready to file, an LLC name can be reserved for 90 days for $25. LLCs and corporations that want to operate under another name adopt an assumed name with the Secretary of State; sole proprietors and partnerships register theirs with the county clerk instead.
Updated October 2026.
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Best LLC Formation Services in Illinois (2026)
Our ranked picks for forming your LLC once your name is clear in Illinois are below, starting with Mainstay Filing. Each entry lists the yearly price and what the service covers.
| Rank | Provider | Best for | Price | What’s included |
|---|---|---|---|---|
| 1 | Mainstay Filing | Forming an LLC with the agent, EIN and annual report included | $199/year + state fee at cost | LLC formation filing, registered agent for the year, EIN application, annual report preparation and filing |
| 2 | IL Registered Agent.org | Illinois registered agent service only | $99/year | $99 per year, flat; in-state street address for the registered office; legal documents served on the company are scanned and sent to the owner online |
| 3 | Illinois Registered Agent.co | Illinois registered agent service only | $99/year | in-state street address for the registered office; legal documents served on the company are scanned and sent to the owner online |
1. Mainstay Filing
Mainstay Filing is our top pick in Illinois. It costs $199/year + state fee at cost and covers lLC formation filing, registered agent for the year, EIN application, annual report preparation and filing. The price stays the same every year, with no add-on menu.
2. IL Registered Agent.org
IL Registered Agent.org is a Illinois registered agent service at $99/year. It provides $99 per year, flat; in-state street address for the registered office; legal documents served on the company are scanned and sent to the owner online. It’s a fit if you only need a registered agent rather than full formation help.
3. Illinois Registered Agent.co
Illinois Registered Agent.co is a Illinois registered agent service at $99/year. It provides in-state street address for the registered office; legal documents served on the company are scanned and sent to the owner online. It’s a fit if you only need a registered agent rather than full formation help.
Illinois name search at a glance
| Topic | Illinois (as of October 2026) |
|---|---|
| Filing office | Illinois Secretary of State, Department of Business Services |
| Search tool | Business Entity Search (free) |
| LLC name reservation | $25 for 90 days (Form no. LLC-1.15) |
| Corporate name reservation | 90 days per name (Form BCA 4.10) |
| LLC assumed name | Prorated on a five-year cycle: $150 in years ending in 0 or 5, $120 in years ending in 1 or 6 |
| Sole proprietor / partnership DBA | Registered with the county clerk under the Assumed Business Name Act |
| LLC Articles of Organization | $150 (form no. LLC-5.5; see the LLC forms page) |
| LLC annual report | $75, due before the first day of the anniversary month |
For a complete list of Illinois formation costs, see Mainstay Filing’s Illinois LLC cost guide.
How to do an Illinois Secretary of State business search
The Department of Business Services keeps the official records of Illinois corporations and LLCs. The search is free and public.
1. Open the Business Entity Search
Go to the Secretary of State’s Business Entity Search. If you have an old bookmark for the separate Corporation/LLC search, start from the Secretary of State’s website instead.
2. Search by name, using the core words
Enter the distinctive words without the ending. For “Lakeshore Loom LLC,” search “Lakeshore Loom” so that corporations, LLCs and similar names all appear. Then repeat with variations: singular and plural forms, numbers written as digits and as words, and the name with and without spaces. Each variation can surface a conflict the first search missed.
3. Look at status and entity type
Open close matches and note whether each one is active, dissolved or revoked, and whether it’s a corporation or an LLC. An active name that isn’t distinguishable from yours will block your filing.
4. Watch for assumed names
Illinois LLCs and corporations register their assumed names with the Secretary of State, so a close match may be another company’s DBA. Treat those as real conflicts for branding purposes.
A search result is a snapshot, not a reservation. Until you reserve the name or the state accepts your Articles, someone else can file it first.
Illinois LLC and corporation name rules
Illinois’s Limited Liability Company Act (805 ILCS 180/1-10) and the Business Corporation Act set the rules. Key points:
- LLC designator: the name must contain “limited liability company,” “L.L.C.” or “LLC.”
- Words an LLC can’t use: Illinois bars LLC names from including “corporation,” “corp,” “incorporated,” “inc,” “ltd,” “co,” “limited partnership” or “L.P.” So “Lakeshore Loom Co. LLC” would be refused.
- Corporate designator: a corporation needs “corporation,” “company,” “incorporated” or “limited,” or an abbreviation of one of them.
- Distinguishable: the name must be distinguishable on the Secretary of State’s records from other entities, reserved names and registered names.
- Regulated words: names suggesting banking, insurance, trust services or a licensed profession may require regulatory approval.
Stuck on ideas? Namechk’s business name generator can produce candidates to test against the Illinois search.
How to reserve a business name in Illinois
Illinois lets you hold a name before forming the business. The terms differ slightly by entity type:
| Entity | Form | Fee | Term |
|---|---|---|---|
| LLC | LLC-1.15 | $25 | 90 days |
| Corporation | BCA 4.10 | See the corporation forms page | 90 days per name |
According to the LLC reservation form, the $25 fee can’t be applied toward the fee for your Articles of Organization. If you’re ready to form the LLC now, skip the reservation and file the Articles directly.
Trademarks, domains and social handles
The Secretary of State’s search won’t show federal trademarks. Search the USPTO trademark database for registered and pending marks before you commit, especially if you plan to sell outside Illinois.
Then check the online side. Namechk shows whether matching domain names and social media handles are available in one search. If the .com is gone, try the domain name generator.
We created a tool that makes it easy.
Assumed names (DBAs) in Illinois
Illinois splits DBA filings between the state and the counties.
LLCs and corporations: file with the Secretary of State
An LLC adopts an assumed name by filing an Application to Adopt an Assumed Name with the Department of Business Services (see the LLC forms page). The fee is prorated on a five-year cycle: $150 in a year ending in 0 or 5, $120 in a year ending in 1 or 6, with smaller amounts in later years of the cycle, so filing late in the cycle costs less but also expires sooner. Corporations file a similar application under the Business Corporation Act.
Sole proprietors and general partnerships: file with the county clerk
Individuals and partnerships doing business under a name other than their own register it with the county clerk in the county where the business is conducted, under the Illinois Assumed Business Name Act. County clerks set the filing process and explain any newspaper publication requirement, so contact your county clerk’s office before filing.
After your search: forming the Illinois business
With a clear name, the next steps are covered in our Illinois LLC guide and the Secretary of State’s Guide for Organizing Domestic LLCs:
- File Articles of Organization (Form no. LLC-5.5, $150) online or by mail with the Department of Business Services.
- Appoint a registered agent with an Illinois address. Mainstay Filing includes one with its formation package; our Illinois registered agent guide explains the rules.
- Get an EIN and register with the Illinois Department of Revenue if you’ll collect sales tax or have employees.
- File the annual report ($75) each year before the first day of your anniversary month. Our Illinois start-a-business guide covers local licenses.
FAQs
How do I search business names in Illinois?
Use the Illinois Secretary of State’s free Business Entity Search. Enter the distinctive words of your proposed name without LLC or Inc., then open close matches to check their status and entity type. LLC and corporate assumed names are filed with the Secretary of State too, so a close match may be another company’s DBA.
How much does it cost to reserve an LLC name in Illinois?
Reserving an LLC name in Illinois costs $25 with Form no. LLC-1.15, and the reservation lasts 90 days. The reservation fee can’t be credited toward the Articles of Organization fee. Corporations reserve names with Form BCA 4.10, also for 90 days per name. Reserving is optional if you’re ready to file.
What words can’t be used in an Illinois LLC name?
Under 805 ILCS 180/1-10, an Illinois LLC name must include limited liability company, L.L.C. or LLC, and it can’t contain corporation, corp, incorporated, inc, ltd, co, limited partnership or L.P. The name must also be distinguishable from other names on the Secretary of State’s records.
How much is an assumed name for an Illinois LLC?
The Illinois fee for an LLC to adopt an assumed name is prorated on a five-year cycle. It is $150 in a year ending in 0 or 5 and $120 in a year ending in 1 or 6, falling in later years of the cycle. The application is filed with the Secretary of State’s Department of Business Services.
Where does a sole proprietor file a DBA in Illinois?
Sole proprietors and general partnerships register an assumed business name with the county clerk in the county where they do business, under the Illinois Assumed Business Name Act. The Secretary of State only handles assumed names for LLCs and corporations. Your county clerk will explain the fee and any publication requirement.
Does an Illinois business search reserve my name?
No. The Business Entity Search shows what’s on file today but doesn’t hold anything. To protect a name before forming, file a name reservation, which lasts 90 days. Filing your Articles of Organization also secures the name once the Secretary of State accepts it. Check federal trademarks as well.
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