Key figures
Illinois compliance
2026, with sources
Qualifying a Delaware corporation
A Delaware corporation doing business in Illinois files an application for authority with the Secretary of State ($150) and pays initial franchise tax on the capital attributed to Illinois. Each year after, it files an annual report ($75) with the annual franchise tax, due before the first day of the month in which it qualified.
Illinois franchise tax is computed on paid-in capital apportioned to Illinois, at 1/10 of 1%. Since 2025 the first $10,000 of liability is exempt, so the tax is zero unless Illinois-apportioned paid-in capital is large.
Returns and the unclaimed property report
Form IL-1120 is due on the 15th day of the 4th month after year end, with an automatic seven-month extension to file (no form needed) for years not ending June 30. The extension does not extend payment.
Unclaimed property — uncashed payroll and vendor checks, customer credit balances — is reported to the Illinois State Treasurer. Business associations file before May 1 for the prior calendar year.
Estimated payments start once the year’s income and replacement tax is expected to exceed $400, due the 15th day of the 4th, 6th, 9th and 12th months; a unitary group pays them on a combined basis under the designated agent’s FEIN.
A year of Illinois filings
Take a Delaware C-corp that qualified in Illinois in March, has a Chicago office and ten employees, and loses money. Each year it files the Secretary of State annual report before March 1 with $75 and a franchise tax computation that, under the $10,000 exemption, comes to zero; it files Form IL-1120 by April 15 (or by the extended date in mid-November) to report the loss and preserve its net loss deduction; it files quarterly IL-941 withholding returns and IDES wage reports; and it files its unclaimed property report with the Treasurer before May 1.
If it has Chicago customers it also files the city’s Form 7550 for the lease transaction tax, a filing that sits with the City of Chicago Department of Finance rather than any state agency and is easy to leave off a compliance calendar built from state sources.
Deadlines
- Before the first day of the corporation’s anniversary monthCorporation annual report and franchise tax to the Secretary of StateAnnual report
- Apr 15 (calendar year); extended to mid-NovemberCorporate income and replacement tax return; automatic seven-month extension to fileForm IL-1120
- Before May 1Unclaimed property report for business associations, covering the prior calendar year
The federal baseline
This page covers what Illinois adds. The federal rules underneath it apply here too.
Common questions
What is the Illinois franchise tax, and will we owe it?
It is a tax on the paid-in capital the Secretary of State attributes to Illinois, collected with the annual report. Since January 1, 2025 the first $10,000 of liability each year is exempt, which takes most early-stage companies to zero franchise tax; the $75 annual report fee is still due.
Do we file an Illinois return if we have a loss?
Yes, if you have net income or loss under Illinois law or are qualified to do business in Illinois and file a federal return. A loss-making company qualified in Illinois still files Form IL-1120 to report the loss and preserve the carryforward.
Compliance next door
- INIndiana complianceIndiana has no franchise tax: a foreign registration, a $31 business entity report every other year, an IT-20 due May 15 and a January 31 withholding reconciliation.
- IAIowa complianceRegister with the Secretary of State for $100, file a $60 biennial report by April 1 of even years, and file the IA 1120 by April 30. No franchise tax applies.
- KYKentucky complianceKentucky compliance is a $90 certificate of authority, a $15 annual report between January and June 30, Form 720 with the LLET, local net profits returns wherever you operate, and an unclaimed property report before November 1.
- MOMissouri complianceQualify with the Secretary of State for $155, file a $20 online annual report in the qualification month each year, and file the MO-1120 by the 15th day of the fourth month.
- WIWisconsin complianceWisconsin asks for a foreign registration with DFI, an annual report each first quarter ($65 online), a franchise tax return with the federal one and an unclaimed property report each November 1.
Founder guides on this
- ComplianceFirst-year compliance calendar for a Delaware C-corpDelaware franchise tax, 1099s, the federal return, payroll filings, state annual reports and sales tax: the deadlines a young C-corp misses most, by month.
- Sales taxSales tax nexus for startups: when you owe tax in a stateSince Wayfair, selling into a state can create a sales tax obligation. How economic nexus works, why SaaS is taxable in some states and when to register.
More of the Illinois guide
- AccountingAccounting and state tax in IllinoisCorporate tax, conformity to federal rules, apportionment and what it does to your books
- ReceivablesReceivables and sales tax in IllinoisSales tax registration, economic nexus, whether SaaS is taxable, and collecting from customers
- PayablesPayables and contractors in IllinoisPaying vendors and contractors: 1099 filing, use tax, contractor tests and withholding
- PayrollPayroll taxes and employer rules in IllinoisWithholding, unemployment insurance, paid leave, minimum wage and the rules on paydays
- AdvisoryAdvisory: credits and decisions in IllinoisCredits, incentives and the decisions that are cheaper to get right the first time
Sources
Checked against each agency’s own page on . Rates and thresholds change, usually on January 1.
General information for US companies, not tax, legal or accounting advice for yours. Rules and thresholds change; confirm the specifics with a CPA or the agency before you act on them.