Illinois Business Entity Search

3,400,060 Illinois entities indexed from the Illinois SOS. Free public search.

Browse the Illinois registry →

How to search Illinois business entities

Every business that operates legally in Illinois files a public record with the Illinois Secretary of State. That record names the entity, identifies its registered agent for service of process, and tracks every formal filing through dissolution. Those records are open to anyone — that is the legal definition of a public registry.

Corporate.AI is a free, structured front door to Illinois's public business filings. We mirror the state's data, normalize it against records from 49 other jurisdictions, and add the cross-state intelligence (shared officers, shared registered agents, NAICS sector classification, beneficial-ownership signals) that a single-state portal cannot provide. Use the search above to look up any Illinois entity by name, by primary filing number, or by officer.

For absolute freshness — same-day filings, formal certificates of good standing, certified document copies — you should also have the Illinois SOS portal bookmarked. We link directly to it from this page.

About the Illinois SOS

The Illinois Secretary of State is the office of record for every business entity formally registered in Illinois. They maintain the public registry, accept new filings, and issue certificates of good standing. Corporate.AI mirrors and normalizes this data alongside records from 49 other jurisdictions.

Domestic LLC filing fee
~$150
Domestic Corp filing fee
~$150

Illinois business entity search FAQ

How do I search Illinois business entities?▶

Use the search box above to query Corporate.AI for any Illinois-registered LLC, corporation, nonprofit, or partnership. You can also search directly at the Illinois SOS's public registry portal. Corporate.AI consolidates Illinois entity records with cross-state filings (foreign registrations, officer overlap, registered-agent networks) so a single search returns more context than the state portal alone.

Is Illinois business entity search free?▶

Yes. Public Illinois business filings are open records. Corporate.AI never charges to look up an entity, its registered agent, officers, or filing history. The Illinois SOS also offers free public search; premium services (certified copies, certificates of good standing) typically cost $150 or more depending on document type.

What information is included in a Illinois entity search?▶

Each Illinois entity record on Corporate.AI includes the registered legal name, entity type (LLC, Corporation, LP, Nonprofit), formation date, current status, primary filing number assigned by the Illinois SOS, registered agent (when published), officer roster (when published), and full filing history. We also surface entities that share officers, registered agents, or NAICS sector classifications across all 50 states.

How do I get a Illinois certificate of good standing?▶

A certificate of good standing (sometimes called a certificate of existence or status certificate) must be issued by the Illinois SOS directly — Corporate.AI does not issue official certificates. You can typically request one online from the Illinois SOS for $38–$50 with same-day or 24-hour turnaround. The certificate confirms the entity is in good standing as of the issuance date.

How do I look up a registered agent in Illinois?▶

Every Illinois business entity is required to designate a registered agent — a person or company authorized to receive service of process at a Illinois street address. Corporate.AI's registered-agent index lets you reverse-search: given an agent name, see every Illinois entity that has designated them. This pattern is useful for due diligence, beneficial-ownership analysis, and competitive research. The Illinois SOS's portal supports forward lookup (entity → agent) but typically not reverse lookup.

What's the difference between an LLC and a corporation in Illinois?▶

A Illinois LLC (limited liability company) is the most common entity type for small businesses — it offers liability protection with pass-through taxation and minimal corporate formalities. A Illinois corporation (typically a C-corp or S-corp) is owned by shareholders, governed by a board, and is the standard vehicle for raising outside investment. Formation fees are similar — $150 for an LLC vs $150 for a corporation in Illinois as of 2026 — but the tax, governance, and capital-raising profiles differ significantly.

How recent is the Illinois business data on Corporate.AI?▶

Illinois entity records on Corporate.AI are refreshed from the Illinois SOS's public feed on the cadence the state publishes — daily, weekly, or monthly depending on jurisdiction. Each entity page displays a "last refreshed" timestamp so you can verify how recent the underlying record is. For absolute freshness, cross-check against the Illinois SOS's live portal (linked above) before relying on a record for legal or contractual purposes.

Can I download Illinois business entity data?▶

Yes. Corporate.AI's REST API and MCP server expose Illinois entity records in machine-readable form for licensed use cases — KYC/AML programs, sales prospecting, journalism, academic research. Bulk downloads of the Illinois SOS's underlying data are typically available directly from the state, sometimes free and sometimes for a fee. See our /api page for licensing terms.