Illinois Corporate Tax Calculator
Illinois's top state corporate tax rate is approximately 9.50%. Estimate your federal + state corporate tax below.
What is the corporate tax rate in Illinois?
Illinois's top marginal state corporate income tax rate is approximately 9.50%. C-Corporations pay this on top of the flat 21% federal corporate tax rate. For example, a C-Corp with $150,000 in net income would owe about $31,500 in federal tax and about $14,250 in Illinois state corporate tax, for a combined estimate of about $45,750.
How are S-corps and LLCs taxed in Illinois?
S-Corporations and LLCs are typically pass-through entities: profit isn't taxed at the federal corporate level, but instead flows through to the owner's personal income tax return, taxed at their individual rate. Many states, including Illinois, still apply some form of entity-level or franchise tax to pass-through businesses — this calculator applies Illinois's corporate rate as an illustrative state-level estimate for pass-through entities too, since actual treatment (flat fees, gross receipts tax, elective PTE tax) varies and isn't always a straight percentage of net income.
This is a simplified estimate for general planning purposes only, not tax advice — consult a CPA or tax attorney familiar with Illinois business tax law for guidance specific to your situation.
Frequently Asked Questions
What is Illinois's corporate tax rate?
Illinois's top state corporate income tax rate is approximately 9.50%. C-Corporations pay this in addition to the flat 21% federal corporate tax rate.
Does Illinois have a state corporate income tax?
Yes. Illinois imposes a state corporate income tax with a top marginal rate of approximately 9.50% on C-Corporation net income.
How much corporate tax would a C-Corp pay in Illinois?
A C-Corp with $150,000 in net income in Illinois would owe about $31,500 in federal corporate tax (21%) plus about $14,250 in state corporate tax, for a combined estimate of about $45,750. Use the calculator above with your own numbers for a precise estimate.
Are S-corps and LLCs taxed differently than C-corps in Illinois?
Yes. S-Corporations and LLCs are typically pass-through entities — profit flows to the owner's personal tax return and is taxed at their individual income tax rate instead of a separate corporate rate. Illinois may still apply some entity-level tax to pass-through businesses, which this calculator estimates using the state's corporate rate as an illustrative figure.
Is Illinois a good state to incorporate in for lower taxes?
Illinois has one of the higher state corporate tax rates in the country at approximately 9.50%, so businesses often weigh this against other factors like market access, labor costs, and incentives before deciding where to incorporate.
Is this Illinois corporate tax calculator official tax advice?
No. This tool provides a simplified estimate using approximate federal and Illinois state corporate tax rates. It doesn't account for deductions, credits, apportionment across states, or your personal tax situation. Consult a CPA or tax attorney licensed in Illinois for advice specific to your business.