Illinois DBA: Assumed Name Filing for LLCs vs. the County Filing for Sole Proprietors

If you are operating a business in Illinois under a name other than your legal entity name, you need a DBA (Doing Business As), also called an assumed business name or assumed name. But here is where it gets important: where you file and what you pay depends entirely on your business structure. LLCs file one way. Sole proprietors file another. Get it wrong, and your business may not be legally protected.

This guide breaks down both systems so you know exactly which applies to you, what it costs, and what the timeline looks like.

What Is a DBA in Illinois?

A DBA (or assumed business name) is a legal name under which your business operates. It is different from your registered entity name or your personal name. Examples: you form an LLC called "Smith Ventures LLC," but you want to operate as "The Coffee Lab" or "Smith Financial Coaching." That operating name is your DBA.

Illinois law requires you to register an assumed name before you do business under it. Registering also makes it easier to:

• Open a business bank account under the DBA
• Sign contracts using the DBA
• Meet licensing and credentialing requirements (many do a name check)

For sole proprietors and partnerships, doing business under an unregistered assumed name is a Class C misdemeanor under the Assumed Business Name Act. Note that registering an assumed name does not by itself give you exclusive rights to it.

Two Completely Different Filing Systems

Illinois has split the DBA/assumed name process into two streams based on entity type. This is crucial: if you are an LLC, you do not file with the county. If you are a sole proprietor, you do not file with the Secretary of State.

System 1: LLCs and Corporations File with the Secretary of State

Limited Liability Companies and corporations file assumed names directly with the Illinois Secretary of State, Department of Business Services, (LLCs use Form LLC-1.20; corporations use Form BCA 4.15). Instructions are at https://www.ilsos.gov/departments/business-services/assumed-name-adoptions/llcinstructions.html.

Filing fee: Prorated across the five year cycle: $150 in years ending in 0 or 5, $120 in 1 or 6, $90 in 2 or 7, $60 in 3 or 8, and $30 in 4 or 9 (so $120 for a filing made in 2026). Renewal is $150 for five years.

Processing time: 10 business days standard, with 24 hour expedited review available for an extra fee (confirm the current expedite fee with the Secretary of State).

Name requirements: The assumed name does not need to include "LLC" or "Limited Liability Company," but your registered entity name on file must include one of these designators. The assumed name itself can be anything, as long as it is not already registered in Illinois and is not misleading or confusingly similar to an existing business name in the Secretary of State database.

Once filed, your assumed name is valid statewide. You do not need to file again in individual counties if you expand to other parts of Illinois.

No publication is required for LLC assumed names filed with the Secretary of State.

System 2: Sole Proprietors and Partnerships File with the County Clerk

If you are a sole proprietor (operating as yourself) or a general partnership, you must file an assumed business name certificate with the Illinois County Clerk in every county where your business operates or has an office. This is mandated by the Assumed Business Name Act (805 ILCS 405).

Filing location: County Clerk of the county where you are based (or each county if you operate in multiple counties).

Filing fee: Varies by county. The Cook County Clerk charges $50. The statute sets a $5.00 county indexing and filing fee, but counties add their own charges, and newspaper publication costs come on top.

Total county costs are higher than LLC costs because of the publication requirement. See the publication section below for more detail.

Processing time: Varies by county; check with your County Clerk. The registration is void unless proof of publication is filed within 50 days.

The County Filing Process: Publication Requirement

This is the biggest difference between the LLC filing and the sole proprietor filing. Sole proprietors and partnerships must publish notice of their assumed name in a newspaper of general circulation in the county. LLCs do not.

Publication timeline:

• You must begin publication within 15 days of filing the certificate with the County Clerk
• Publish once per week for 3 consecutive weeks (three separate notices)
• Submit proof of publication to the County Clerk within 50 days of filing the certificate

Publication cost: Newspaper publication charges vary widely by paper and county. Ask several qualifying newspapers for quotes before you file. This is paid directly to the newspaper, not the County Clerk.

Why publication? The law requires public notice so that creditors, the public, and existing businesses know who is behind the assumed name. This transparency is meant to protect the public and prevent deception.

Cook County Specifics

Cook County (which includes Chicago and many suburbs) processes assumed business name filings through the Cook County Clerk's office. The Cook County Clerk's filing fee is $50, and newspaper publication costs are added on top.

If you are a sole proprietor or partnership operating in Chicago or Cook County, expect:

• $50 filing fee to the Cook County Clerk
• Newspaper publication costs (varies by paper; Chicago papers will be higher than suburban papers)

The Cook County Clerk's website is the authoritative source for current fees and procedures specific to Cook County: www.cookcountyclerkil.gov.

If you are an LLC operating in Cook County, you file your assumed name with the Illinois Secretary of State online, not the Cook County Clerk. You pay the prorated assumed name fee ($30 to $150 depending on the year) to the SOS and are done. No county filing or publication is required.

Side-by-Side Comparison

Aspect	LLC (Secretary of State)	Sole Proprietor (County Clerk)
Where to file	Illinois Secretary of State (online)	County Clerk of residence/operation county
Filing fee	$30 to $150, prorated by year	Set by county ($50 in Cook) + publication
Processing time	10 business days	Varies by county (plus publication time)
Publication required	No	Yes (3 weeks in newspaper)
Valid statewide	Yes	Only in filed county (refile in other counties if needed)
Online filing available	Yes	Varies by county; often paper-based

When You Actually Need a DBA in Illinois

You need to file a DBA if you are doing any of the following:

• Operating under a name other than your registered entity name or your legal name
• Selling online under a brand name different from your company name
• Franchising or licensing your brand
• Applying for certain licenses or permits (many agencies require a registered assumed name before issuing credentials)
• Opening a business bank account (most banks require a filed DBA or entity registration)

You do not need a separate DBA if you operate under your registered entity name exactly as it appears in your Articles of Organization (or Articles of Incorporation). For example, if your LLC is named "Smith Ventures LLC" and you operate only as "Smith Ventures LLC," no DBA is necessary.

How to File Your DBA in Illinois

If You Are an LLC:

1. Go to the Secretary of State's assumed name instructions at https://www.ilsos.gov/departments/business-services/assumed-name-adoptions/llcinstructions.html
2. Select "Assumed Name" or "Form LLC-1.20" from the filing options
3. Enter your current LLC name and your desired assumed name
4. Provide your registered agent and office address
5. Pay the prorated filing fee ($30 to $150 depending on the year)
6. Your filing will be processed within 10 business days

If You Are a Sole Proprietor:

1. Contact the County Clerk in the county where you operate
2. Request the assumed business name application (often called a "Certificate of Assumed Business Name" or similar)
3. Complete the form with your legal name, the assumed name, and your business address
4. File the form with the County Clerk and pay the filing fee
5. Within 15 days, submit a "Notice of Assumed Business Name" to a local newspaper for publication
6. Once the newspaper publishes your notice for 3 consecutive weeks, obtain proof of publication
7. File the proof of publication with the County Clerk within 50 days of your original filing
8. Your assumed name registration is now complete and valid for the specified period (typically 5 years)

Renewal and Ongoing Compliance

Both LLCs and sole proprietors must renew their assumed business name registrations periodically.

LLCs: Renewal is $150 for a five-year term. You should receive a renewal notice from the Secretary of State before your current registration expires. Renew online using the same portal where you filed the original assumed name.

Sole Proprietors: Renewal rules and fees are set by each county. Ask your County Clerk when your registration must be renewed, what it costs and whether publication is required again.

Common Mistakes to Avoid

• Filing with the wrong agency: LLCs must use the Secretary of State. Sole proprietors must use the County Clerk. Filing in the wrong place means your assumed name is not legally registered.
• Skipping publication: Sole proprietors often underestimate publication costs and timelines. Allow at least three weeks of publication, plus time to file proof within 50 days, and get newspaper quotes in advance.
• Not renewing on time: Letting an assumed name registration lapse means you are no longer registered to use that name. Set a reminder for your renewal deadline.
• Operating in multiple counties without filing in all of them: Sole proprietors are required to file in every county where they operate. Do not file only in one county and assume it covers you statewide.

Additional Resources

Illinois Secretary of State, Department of Business Services: https://www.ilsos.gov/departments/business-services.html

Secretary of State Business Search: https://apps.ilsos.gov/businessentitysearch/ (check if a name is already registered)

Cook County Clerk: www.cookcountyclerkil.gov

Illinois Department of Revenue (for sales tax and other business registration): https://tax.illinois.gov/businesses/registration.html

Disclaimer

This guide is informational only and does not constitute legal or tax advice. Business formation and naming rules are complex and can depend on your specific situation, the nature of your business, and local ordinances. For guidance on whether you need a DBA, how to structure your entity, or how to comply with Illinois law, consult with a qualified Illinois business attorney or accountant.

Fees and procedures are accurate as of October 2026 and are subject to change. Always verify current fees and requirements with the Illinois Secretary of State or your County Clerk before filing.