Illinois uses 4.95% flat income tax rate in the current TaxGuide Pro calculator data. Estimate Illinois quarterly tax payments for 2025, 2026, or 2027 planning by entering projected income, withholding, and credits. The tool compares projected liability with expected withholding and suggests whether estimated payments may be needed.
Estimates use Illinois’s flat tax rate and are not a substitute for official payment calculations.
Illinois estimated tax calculator
Illinois uses 4.95% flat income tax rate in the current TaxGuide Pro calculator data. Estimate Illinois quarterly tax payments for 2025, 2026, or 2027 planning by entering projected income, withholding, and credits. The tool compares projected liability with expected withholding and suggests whether estimated payments may be needed.
State-specific estimate, next-step notes, and official Illinois source links.
Illinois state facts
Examples use 2026 taxable income before credits or residency allocation. Use the official state source below to verify final filing guidance.
Illinois uses 4.95% flat income tax rate in the current TaxGuide Pro calculator data.
$60,000 single taxable income -> about $2,970 state income tax before credits.
$120,000 married filing jointly taxable income -> about $5,940 state income tax before credits.
Illinois deductions and exemptions depend on filing status and state instructions; verify the current return before filing.
Review dependent, household, income-based, and other Illinois credits in the state credit finder, then confirm eligibility in official instructions.
For a 2026 return filed in 2027, confirm the due date in published Illinois instructions. State deadlines and disaster relief can differ from federal dates.
Illinois does not guarantee one refund date for every return. E-filed, accurate returns with direct deposit are generally processed faster than paper or reviewed returns.
Official verification: Illinois Department of Revenue.
No. This tool focuses on Illinois state tax estimates only. Federal estimates are separate.
Illinois uses 4.95% flat income tax rate in the current TaxGuide Pro calculator data. The examples on this page use taxable income before credits, so final results can change when state deductions, credits, or residency allocation apply.
Illinois retirement income treatment can depend on the income type, age, and state exclusions. Use the Illinois retirement tax checker for a state-specific review.
Illinois Social Security treatment can differ from federal treatment. Use the Illinois Social Security checker and verify the result with the official state source.
Illinois refund timing depends on e-file versus paper filing, direct deposit, return accuracy, identity verification, and seasonal volume. Use the Illinois refund timeline estimator and the official refund-status source for live updates.
Use the official Illinois revenue or tax agency sources linked in the sources section. TaxGuide Pro is an educational estimator and does not replace a filed state return or agency notice.
Last updated August 20, 2026.
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