Sole Proprietorship in Illinois: How to Start One

A sole proprietorship is the default legal structure for anyone in Illinois who starts doing business without filing formation paperwork with the state. If you start selling a product or offering a service under your own name and never file Articles of Organization or Articles of Incorporation, you are already operating as a sole proprietor. This guide walks through what an Illinois sole proprietorship actually requires: when you need to file an assumed business name, how to register for taxes, which licenses might apply, and what mistakes tend to cost new business owners the most time and money.

This article is informational only and is not legal or tax advice. Illinois rules vary by county and industry, so confirm requirements that affect your specific business with a licensed attorney or CPA before you rely on anything here.

What Is an Illinois Sole Proprietorship?

An Illinois sole proprietorship is an unincorporated business owned and run by one person, where there is no legal separation between the owner and the business. There is no Secretary of State filing to create one and no annual report to keep it in good standing. The tradeoff is personal liability: if the business is sued or can't pay a debt, the owner's personal assets, including savings, a car, or a home, can be reached to satisfy that obligation. That is the core difference between a sole proprietor and someone who forms an LLC or corporation, which creates a separate legal entity and generally shields personal assets from business debts.

If you want liability protection, a sole proprietorship is not the right structure and you should look into forming an Illinois LLC instead. If you are testing an idea, freelancing, or running a small side business and are comfortable with the liability tradeoff, a sole proprietorship in Illinois is the fastest and cheapest way to start.

What You'll Need

A business name (your own legal name, or a made-up "doing business as" name)
Your Social Security number, or an Employer Identification Number (EIN) from the IRS if you plan to hire employees or want to keep your SSN off business paperwork
An assumed business name filing with your county clerk, if you're using a name other than your own legal name
A MyTax Illinois account and Form REG-1, if you'll sell taxable goods or services, hire employees, or owe certain other state taxes
Any occupation-specific state license required for your line of work (contractors, cosmetologists, real estate agents, and similar regulated fields)
Any local business license or permit required by your city, village, or county
A separate business bank account (strongly recommended, not legally required)
Basic business insurance, such as general liability coverage, given that a sole proprietorship offers no legal liability shield

Step-by-Step: How to Start a Sole Proprietorship in Illinois

Step 1: Choose Your Business Name

You can operate under your own full legal name with no filing at all. For example, if Maria Alvarez wants to do freelance bookkeeping as "Maria Alvarez," she doesn't need to register a name with anyone. But most sole proprietors want a business-sounding name, like "Alvarez Bookkeeping Services," and that requires an assumed name filing (see Step 2).

Before you commit to a name, search the Illinois Secretary of State's business entity database to see if an LLC or corporation is already using it. This database does not cover sole proprietor assumed names, since those are filed at the county level, but it's still a useful first check to avoid picking a name that collides with a registered entity: apps.ilsos.gov/businessentitysearch.

Step 2: File an Assumed Business Name With Your County Clerk (If Needed)

Under the Illinois Assumed Business Name Act (805 ILCS 405), any sole proprietorship or general partnership operating under a name other than the owner's real name must file an assumed name certificate with the County Clerk in every county where the business operates. This is different from LLCs and corporations, which file their assumed names with the Secretary of State.

The statutory county filing and indexing fee is $5.00, though individual counties commonly add their own recording charges on top of that base fee, so confirm the total with your specific county clerk's office before you file. Illinois law also requires you to publish notice of the assumed name once a week for three consecutive weeks in a newspaper of general circulation in the county where the business is located. Your county clerk's office can typically point you to an approved local paper for this, and some clerks bundle the publication into their filing packet.

Step 3: Get an EIN From the IRS (If Applicable)

A single-member sole proprietorship with no employees can legally use the owner's Social Security number for tax purposes and skip an EIN entirely. That said, many owners get one anyway because banks often require it to open a business checking account, and it keeps your SSN off client-facing paperwork like invoices and 1099 forms. If you plan to hire employees, you are required to get an EIN. Applying directly through the IRS is free.

Step 4: Register With the Illinois Department of Revenue

If your business will sell taxable goods or services, hire employees, or owe certain excise or withholding taxes, you need to register with the Illinois Department of Revenue (IDOR) using Form REG-1 through MyTax Illinois. Registration is free. Online applications typically process in one to two business days, while paper applications submitted by mail can take four to six weeks.

If you're selling taxable goods, you'll be issued a Certificate of Registration that must be displayed at your place of business, and you'll be responsible for collecting and remitting Illinois's 6.25% state sales tax rate, plus any applicable local sales taxes on top of that. Register here: tax.illinois.gov/businesses/registration.

As a sole proprietor, your business income and losses pass through to your personal tax return (IRS Schedule C, and the Illinois equivalent), and Illinois taxes that net income at the flat personal income tax rate of 4.95%. There is no separate Illinois entity-level income tax for sole proprietorships the way there is for corporations. General information from the Illinois Department of Revenue is available at tax.illinois.gov.

Step 5: Check for a State Occupational License

Illinois does not issue one general statewide business license that every sole proprietor needs. Instead, specific regulated occupations and activities require their own license from the relevant state agency. Common examples include contractors, cosmetologists and barbers, real estate agents, insurance agents, home daycare providers, and businesses selling alcohol. Most of these professional and occupational licenses run through the Illinois Department of Financial and Professional Regulation, with a handful of other activities licensed by separate state agencies. If your work falls into a regulated category, confirm your specific licensing requirement before you start taking clients or customers.

Step 6: Check Local License and Permit Requirements

Beyond state-level rules, many Illinois cities, villages, and counties require their own local business license, home occupation permit, or zoning sign-off, especially if you're running the business from a residential address or a physical storefront. Chicago, for instance, has its own business licensing structure separate from anything the state requires. Call or check the website for the city or county where you'll be operating before you open your doors.

Step 7: Open a Separate Business Bank Account

Nothing in Illinois law forces a sole proprietor to keep business and personal money in separate accounts, but doing so anyway is one of the most useful habits you can build early. It makes bookkeeping dramatically simpler at tax time, makes it easier to prove business expenses if you're ever audited, and it's usually required by the bank if you want to accept payments or write checks under your assumed business name rather than your personal name.

Step 8: Consider Insurance

Because a sole proprietorship provides no separation between your personal assets and your business liabilities, insurance is doing work that an LLC's legal structure would otherwise do for you. General liability insurance is the most common starting point, and depending on your industry you may also want professional liability, commercial auto, or a business owner's policy. Get quotes from an independent insurance agent who can compare options for your specific type of business.

Tips and Common Mistakes to Avoid

Skipping the assumed name filing. Operating under a business name without filing it with your county clerk can create problems opening a bank account, signing contracts, and in some cases can carry legal consequences under the Assumed Business Name Act.
Forgetting the publication requirement. Filing the assumed name certificate alone isn't the full requirement; the three-week newspaper publication is part of the statute, and some clerks won't consider the filing complete until you've submitted proof of publication.
Assuming a name search on the Secretary of State site covers sole proprietors. That database only shows LLCs and corporations. Two sole proprietors could legally have very similar assumed names registered in different counties, so a thorough name search matters if you plan to build a brand.
Mixing personal and business finances. This is the single most common bookkeeping mistake among sole proprietors, and it makes both tax prep and any future liability defense much harder.
Not registering for sales tax before your first sale. If you owe Illinois sales tax and don't have a Certificate of Registration in hand, you're exposed to penalties on tax you should have been collecting from day one.
Assuming no state filing means no liability risk. A sole proprietorship's simplicity is also its biggest drawback: there's no legal wall between your business and your personal assets. If that risk doesn't sit well with you as the business grows, forming an LLC is worth evaluating.
Overlooking local rules. State-level research isn't the whole picture. City and county licensing, zoning, and home occupation rules catch a lot of new business owners off guard.

What to Expect After You Start

Once your assumed name filing is complete (if you needed one) and you're registered with the Illinois Department of Revenue where applicable, you can generally begin operating and invoicing clients. Processing times can vary by county clerk and by how MyTax Illinois is running that week, so build in a little buffer before you count on having everything in hand. Many owners find that the administrative side of a sole proprietorship stays fairly light year to year since there's no state annual report to file the way LLCs and corporations have, though your county's assumed name certificate will eventually need renewal and your tax filings continue on their normal schedule regardless of business structure.

Results and timelines can vary based on your county, your industry, and how quickly you complete each step, so treat the ranges above as planning estimates rather than guarantees.

Sole Proprietorship vs. LLC: A Quick Note

A lot of Illinois sole proprietors eventually ask whether they should convert to an LLC. The honest answer depends on your risk exposure and growth plans. An LLC costs more to set up and maintain (a $150 Articles of Organization filing plus a $75 annual report each year through the Secretary of State), but it creates a legal entity separate from you personally, which limits how much of your personal wealth is on the line if the business is sued or can't pay its debts. If you're a freelancer with minimal liability exposure and want to stay as simple and cheap as possible, sole proprietorship is often enough. If you're taking on business debt, hiring employees, or working in a field with real liability risk (contracting, consulting, anything involving client property or safety), it's worth having an attorney walk you through whether an LLC makes more sense for your situation.

Where to Get Help

The Illinois Small Business Development Center network offers free, one-on-one advising for new and existing business owners across the state, including help thinking through registration, licensing, and early financial planning: sbdc.illinois.gov. The U.S. Small Business Administration's Illinois district office is another free resource for state-specific guidance: sba.gov/district/illinois.

This article is for general informational purposes only and does not constitute legal or tax advice. Illinois business requirements can vary by county, city, and industry, and rules can change. Before you file anything or make decisions about your business structure, consult a licensed Illinois attorney and a CPA familiar with your specific situation.