State estimated tax — 2026

Illinois Estimated Tax Payments 2026

Who has to make Illinois quarterly estimated payments, the 2026 due-date calendar, the safe-harbor rules that avoid an underpayment penalty, and how to pay through MyTax Illinois.

Who must pay

File Form IL-1040-ES once you can reasonably see your 2026 Illinois liability topping $1,000 after subtracting Illinois withholding, pass-through entity withholding, and credits.

2026 due-date calendar

Installment	% of annual estimate	Due date	Note
Q1	25%	April 15, 2026	—
Q2	25%	June 15, 2026	—
Q3	25%	September 15, 2026	—
Q4	25%	January 15, 2027	—

Illinois divides the annual required payment into four equal 25% installments — there is no unequal schedule like California’s. Farmers (at least ⅔ of total federal gross income from farming) are fully exempt from making any estimated payments at all, not merely given a reduced percentage.

Safe harbor — avoiding the underpayment penalty

Form IL-2210’s late-payment penalty steps aside once your timely payments reach the smaller of 90% of your real 2026 tax or 100% of your 2025 tax. Illinois’s flat 4.95% rate carries through to this rule too — there’s no separate, costlier tier that kicks in once a filer’s income gets large, unlike the tiered approach several neighboring states use above a set income mark.

How to calculate your payment

Estimate your annual Illinois tax, test it against the safe harbor above, then split the required annual payment across the installments in the calendar. The site's quarterly planner handles the math and the federal side together.

Open the quarterly estimated tax calculator → Check your underpayment penalty exposure →

How to pay

Pay online through MyTax Illinois, or mail a check or money order with the Form IL-1040-ES voucher. Illinois requires electronic payment once your annual individual income tax liability reaches $200,000 — a far higher bar than most states’ e-pay mandates. Once triggered, all future tax payments must be made electronically, for example through MyTax Illinois.

Penalty basics

Illinois multiplies the tax due by its published annual rate and divides by 365 to get daily underpayment interest. That rate held at 7% from January 1, 2025 through December 31, 2026, reviewed by the Department every January 1 and July 1 and tied to the federal short-term rate under IRC §6621.

Illinois-specific notes

Not one Illinois municipality — Chicago included — levies its own income tax on individuals; the flat 4.95% is entirely a state-level charge. A 6.06% slice of collections does flow to local governments through the Local Government Distributive Fund, but that’s revenue-sharing between the state and cities, not a separate bill to taxpayers.
A farmer whose total federal gross income is at least two-thirds farming-derived owes Illinois NO estimated payments at all — a complete pass, not merely a lower percentage the way the federal 66⅔% rule works elsewhere. Illinois’s own forms mention only “farmer,” with no parallel fisherman carve-out.
Illinois waits until $200,000 of annual liability before mandating electronic payment — a bar so much higher than comparable states’ mandates that almost no individual filer will ever bump into it.

See the Illinois 2026 tax brackets for current rates, or the Illinois state tax calculator to estimate your full-year liability.

Frequently asked questions

When are Illinois estimated tax payments due in 2026?

The four Illinois due dates for 2026 are April 15, 2026, June 15, 2026, September 15, 2026, January 15, 2027. Illinois divides the annual required payment into four equal 25% installments — there is no unequal schedule like California’s. Farmers (at least ⅔ of total federal gross income from farming) are fully exempt from making any estimated payments at all, not merely given a reduced percentage.

Do I owe Chicago or another local income tax alongside my Illinois estimate?

No. No Illinois city or county — Chicago included — imposes an individual income tax; the entire liability is state-level at a flat 4.95%. A portion of what the state collects gets shared back to municipalities through the Local Government Distributive Fund, but that’s a distribution mechanism, not a tax you owe separately.

Are Illinois farmers excused from estimated tax entirely, or just given a break?

Excused entirely. Cross the two-thirds-of-gross-income-from-farming line and Illinois waives estimated payments outright — a bigger concession than the reduced-percentage relief that the federal government and most other states offer farmers instead.

Does Illinois raise its safe-harbor bar for wealthier taxpayers the way some states do?

No. Illinois’s flat 4.95% rate carries through to the safe-harbor rule as well — every filer clears it at the same 90% (current-year) or 100% (prior-year) mark, with nothing resembling a higher tier for large incomes.

How do I pay Illinois estimated tax?

Pay online through MyTax Illinois, or mail a check with the Form IL-1040-ES voucher. Illinois requires electronic payment once your annual individual income tax liability reaches $200,000 — a far higher bar than most states’ e-pay mandates. Once triggered, all future tax payments must be made electronically, for example through MyTax Illinois.

Estimated tax in other states

Compare how Illinois stacks up against the other states with a Rising search trend for estimated-tax rules.