Illinois LLC Taxes

Illinois LLC owners usually deal with two layers of tax: the federal default treatment of the LLC and the state's own income, sales, and business-tax rules. This guide is rendered from the current source-backed tax profile for Illinois, so the rates, deadlines, and registration links below match the checked-in official sources used for periodic refreshes.

At a Glance

Topic	Current treatment
Federal default for a single-member LLC	Disregarded entity (Schedule C)
Federal default for a multi-member LLC	Partnership (Form 1065)
State individual income tax	Yes — 4.95%
Separate LLC business tax	Yes
State sales tax	Yes — 6.25%
PTE election	Available

How Illinois LLCs Are Taxed Federally

By default, a single-member LLC is taxed federally as a disregarded entity and a multi-member LLC is taxed as a partnership. In practical terms, that means the LLC is usually a pass-through business unless the owners elect S corporation or C corporation treatment. Illinois does not change those federal defaults just because you formed an LLC under state law.

If you elect S corporation status, the election can change how payroll and self-employment taxes work, but it does not erase state filing or business-tax obligations. The same caution applies to a C corporation election: changing federal classification can change the state tax treatment, but it does not replace the state's separate minimum, franchise, margin, or sales-tax rules.

Illinois State Income Tax for LLC Owners

Illinois taxes pass-through LLC income at the owner level. The current profile flags the state as flat and uses a headline rate of 4.95%.

Illinois uses a flat individual income tax rate.

If you expect to owe state tax during the year, the current profile lists estimated-tax dates as April 15, June 15, September 15, and January 15. Always confirm the current tax-year calendar before submitting payments because estimated-tax timing can change.

LLC-Specific Business Taxes

Some states impose a separate business tax even when the LLC is otherwise taxed as a pass-through. The current Illinois profile shows:

Other (c corp, s corp, partnership): Illinois replacement tax applies at 2.5% for C corporations and 1.5% for S corporations and partnerships.

This matters because owners often assume pass-through treatment means the entity itself has no state-level tax cost. In many states that is wrong. A minimum annual tax, franchise tax, margin tax, or gross receipts tax can apply even if the LLC does not owe ordinary state income tax.

Sales Tax and Registration

Illinois has a base statewide sales tax rate of 6.25%. Local taxes and special district rates can increase the combined Illinois rate.

If your LLC sells taxable goods or taxable services in Illinois, review registration with Illinois Department of Revenue before you start collecting tax. The current registration link is: https://tax.illinois.gov/businesses/registration.html.

Even when the base state rate looks simple, local add-ons, marketplace rules, and product-specific exemptions can change the real compliance burden. Use the official rate lookup and registration portal instead of relying on a static combined-rate number copied from an old article.

Pass-Through Entity Election

Illinois currently offers a pass-through entity tax election. The profile lists a rate of 4.95%, an election deadline of Election is made on the return for the tax year, and eligible entities of partnership, s_corp.

Publication 129 is the checked-in source for Illinois pass-through entity treatment in this rollout.

State-Specific Tax Quirks

Replacement tax layer: Illinois entity tax content should always mention replacement tax, not just the headline income tax rate.

Bottom Line

For a Illinois LLC, the main questions are not just whether the state has income tax. You also need to confirm any separate business tax, the sales-tax registration trigger, and whether a PTE election is actually available for your entity type. This page is intentionally tied to the checked-in tax profile so it can be refreshed from the same official sources during future tax updates.