Illinois Estimated Tax Deadlines — 2026
2026 estimated tax payment deadlines for each quarter. Avoid penalties by filing on time.
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Quick Illinois Tax Estimate
Based on Illinois's tax rates for 2026. Enter your details for a personalized calculation.
State Tax on $80K Profit
$0
SE Tax
$11,303.64
Effective Rate
20.2%
Marginal Rate
12%
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Illinois Tax Information
State Income TaxYes
Sales Tax0%
LLC Filing Fee$0
Annual Report Fee$None
Standard DeductionN/A
Self-employed pay both federal and Illinois state tax.
Illinois Quarterly Tax Deadlines
Q1
Apr 15
Q2
Jun 16
Q3
Sep 15
Q4
Jan 15
Frequently Asked Questions
What are the 2026 quarterly tax deadlines for Illinois?
Federal deadlines: April 15, June 16, September 15, 2026, and January 15, 2027. Illinois follows the same schedule. Payments postmarked by the deadline are considered on time.
How do I avoid underpayment penalties in Illinois?
Pay at least 90% of current year tax OR 100% of prior year tax (110% if AGI > $150K) through withholding and quarterly estimates combined.
Disclaimer:This calculator provides estimates for informational purposes only. It does not constitute tax advice, financial advice, or legal advice. Tax laws change frequently and vary by individual circumstances. Results may not reflect your actual tax liability. Always consult a qualified CPA, tax professional, or financial advisor before making tax decisions. For official tax information, visit IRS.gov.