Illinois business entity information, including entity name, type, file number, and formation date, is available through the Illinois Secretary of State's Business Entity Search portal. This online database provides the details you need for onboarding, compliance, or business transactions. The sections below cover how to search the database and where to find each data point.

Summary table: finding your Illinois entity information

The table below shows where each data point lives in Illinois's system, what it looks like, and any state-specific notes.

How to search for Illinois business entities

The Business Entity Search covers Corporations, Not-for-Profit Corporations, Limited Partnerships, Limited Liability Companies, and Limited Liability Partnerships, and it is the single search tool for all of them.

The search page offers eight search methods: Business Name, Illinois registered agent name, President, Secretary, Manager, File Number, Keyword, and Partial Word. The form also presents input fields for Last Name, First Name, Middle Initial, and Business Name. Keyword and Partial Word are offered as separate name search methods.

What you'll see in search results

According to the ILSOS business search page, the File Detail Report displays the Official Name, Date of Formation/Registration, Jurisdiction, Name of Registered Agent, Address of Registered Office, and Status. For corporations it adds the names and addresses of the president and secretary; for LLCs it lists the names and addresses of any managers. The fields shown depend on entity type.

How to find your file number in Illinois

For corporations, the file number is a unique number the Illinois Secretary of State assigns at qualification.

Where to locate your Illinois file number

1. Illinois business search (fastest method): Available as a dedicated search input on the Business Entity Search portal.

2. ILSOS filing forms: Corporation forms such as Form BCA 14.30 include a field reserved for the office-assigned file number.

3. States that require annual report filings: Labeled "Corporation File Number" on the ILSOS annual report portal.

Illinois file number format

ILSOS assigns each corporation an 8-digit numeric file number at qualification. The state has not published the internal check-digit or validation logic behind that format, and it has not published an equivalent format specification for LLC file numbers.

How to find your entity type in Illinois

Illinois recognizes multiple business entity types, each governed by its own statute, and the Business Entity Search database covers Corporations, Not-for-Profit Corporations, Limited Partnerships, Limited Liability Companies, and Limited Liability Partnerships.

Illinois also recognizes Series LLCs under 805 ILCS 180/37-40, Limited Liability Limited Partnerships under the Uniform Limited Partnership Act (2001) at 805 ILCS 215/201, and Professional Service Corporations under 805 ILCS 10/3.4. Illinois's low-profit limited liability company (L3C) provisions, at 805 ILCS 180/1-26, remain active law and have not been repealed.

LPs, LLPs, and LLLPs are searchable through the main Business Entity Search. The formerly separate LP/LLP search page now points users to the unified portal, per the ILSOS LP LLP notice.

General partnerships and sole proprietorships are not registered with the Illinois SOS. When they operate under an assumed name, the Assumed Business Name Act requires them to file a certificate with the County Clerk of the county where they conduct business.

Where to find your Illinois entity type

1. Illinois business search (most accessible): Shown in the Business Entity Search results listing; entity type is not one of the enumerated File Detail Report fields. Listed as "LLC," "Corporation," "Not-for-Profit," "LP," "LLP," etc.

2. Formation documents: Use full legal terminology (e.g., "Articles of Organization" for an LLC).

How to find your formation date in Illinois

The portal's File Detail Report shows the date the entity's formation or registration was filed with the Secretary of State, labeled "Date of Formation/Registration."

Where your Illinois formation date appears

1. Illinois business search (easiest access): Displayed in the File Detail Report.

2. Filing confirmation: Per the ILSOS LLC filing instructions, confirmation is delivered by email after the Department of Business Services examines and approves the document.

3. Annual report due dates: The original filing date anchors your Illinois annual report requirements: under 805 ILCS 180/50-1, an LLC's report is due within 60 days immediately preceding the first day of its anniversary month. Corporations follow the same anniversary-month window under 805 ILCS 5/14.10, unless they have elected an extended filing month under 805 ILCS 5/14.01.

Formation date vs. effective date

Illinois law allows business entities to select a delayed effective date, so the formation date and effective date are not always the same. Under 805 ILCS 180/5-5, an LLC is organized when its articles are filed by the Secretary of State or at a later time specified in the articles, not more than 60 days after filing.

For corporate amendments, the maximum delay is 30 days after filing under 805 ILCS 5/10.35; for mergers and consolidations, 30 days under 805 ILCS 5/11.40. Section 10.35 sets effectiveness at the later of the filing date or the stated date, and Section 11.40 makes a merger effective upon filing or on a later specified date, so an effective date cannot precede the filing date.

Simplify Illinois entity compliance with Discern

Once you have pulled your entity name, type, file number, and formation date from the ILSOS portal, keeping those records current across every filing deadline is a separate job. Discern provides registered agent service and annual report filing for Illinois entities, so the details you just looked up stay attached to a system that tracks them going forward instead of living in a one-time search result.

Firms that hold registrations in Illinois and other states can keep registered agent service, annual report filings, and entity records for every jurisdiction in one place with Discern, rather than re-running a state-by-state search each time a filing comes due.

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Frequently asked questions about Illinois entity searches

These questions cover the details compliance teams ask most often about Illinois entity records.

Is there a separate Illinois search tool for LPs and LLPs?

No. The former standalone LP/LLP search has been merged into the unified Business Entity Search, which covers corporations, not-for-profits, LLCs, LPs, and LLPs in one place.

What format is an Illinois file number?

Corporation file numbers are 8-digit numeric identifiers assigned at qualification. The state has not published a format specification for LLC file numbers.

Can an Illinois entity's effective date come before its formation date?

No. Documents take effect on the later of the filing date or a date stated in the document, capped at 60 days after filing for LLC articles of organization and 30 days for corporate amendments and mergers.

How do I search if I only know part of a business name?

Use the portal's Keyword or Partial Word search methods, which are listed alongside the six other search options.