Illinois Estimated Tax Payments 2026

Illinois’s test is expected 2026 tax liability above $1,000 after your Illinois withholding, pass-through withholding and the credits the form lists (income tax paid to other states, Illinois property tax, K-12 education expenses, volunteer emergency worker, earned income, child tax, pass-through entity tax and Schedule 1299-C credits). If you plan to file a joint return, the form says to figure your estimated tax on your joint income.

• You must make estimated income tax payments if you reasonably expect your 2026 tax liability to exceed $1,000 after subtracting your Illinois withholding, pass-through withholding and the tax credits the form lists.

  “You must make estimated income tax payments if you reasonably expect your 2026 tax liability to exceed $1,000 after subtracting your Illinois withholding, pass-through withholding, and tax credits for”

• You will likely need to make estimated payments if your income is either fully or partially exempt from Illinois withholding.

  “You will likely need to make estimated payments if your income is either fully or partially exempt from Illinois withholding.”

• You do not have to make estimated payments if you are 65 years or older and permanently living in a nursing home, a farmer, or if you were not required to file an IL-1040 in the prior year; you are a farmer if at least two-thirds of your total federal gross income is from farming.

  “You do not have to make estimated payments if you are 65 years or older and permanently living in a nursing home, a farmer, or if you were not required to file an IL-1040, Illinois Individual income Tax return in the prior year. We consider you a farmer if at least two-thirds of your total federal gross income is from farming.”

The IL-1040-ES worksheet starts from the Illinois base income you expect in 2026, subtracts the exemption amount, multiplies the result by 4.95%, adds any surcharges, and subtracts expected withholding and credits. If the result is $1,000 or less you stop; if it is more, line 11 divides it by four and rounds to whole dollars. It is a worksheet estimate, not an assessment of your actual liability.

• Worksheet line 4: Multiply Line 3 by 4.95% (.0495).

  “Multiply Line 3 by 4.95% (.0495).”

• Worksheet line 10: if $1,000 or less, stop; you do not have to make estimated tax payments at this time. If more than $1,000, continue to Line 11.

  “If $1,000 or less, stop. You do not have to make estimated tax payments at this time. If more than $1,000, continue to Line 11.”

• Worksheet line 11: Divide Line 10 by 4, and round the result to whole dollars. This is the amount of each of your estimated tax payments.

  “Divide Line 10 by 4, and round the result to whole dollars. This is the amount of each of your estimated tax payments.”

• If you determine that you are required to make estimated payments, you should pay 100 percent of the tax.

  “If you determine that you are required to make estimated payments, you should pay 100 percent of the tax.”

• However, if you pay at least 90 percent of this year’s tax or at least 100 percent of last year’s tax in four equal timely installments, you may not be subject to this penalty.

  “However, if you pay at least 90 percent of this year’s tax or at least 100 percent of last year’s tax in four equal timely installments, you may not be subject to this penalty.”

The form gives no separate January 15 skip date or farmer deadline; farmers are listed as an exception to paying at all. If your income arrives unevenly or you start paying mid-year, Publication 105 says you may be able to annualize your income, using Form IL-2210.

• Your first estimated payment is due by April 15, 2026. You may either pay all of your estimated tax at that time or pay it in four equal installments due April 15, 2026; June 15, 2026; September 15, 2026; and January 15, 2027.

  “Your first estimated payment is due by April 15, 2026. You may either pay all of your estimated tax at that time or pay your estimated tax in four equal installments that are due on April 15, 2026; June 15, 2026; September 15, 2026; and January 15, 2027.”

• Installment dates are the following, unless the date falls on a weekend or holiday, then the payment will be due on the next business day.

  “Installment dates are the following, unless the date falls on a weekend or holiday, then the payment will be due on the next business day.”

• If you file on a fiscal-year basis, adjust all the due dates to correspond to your tax year.

  “Note: If you file on a fiscal-year basis, please adjust all the due dates to correspond to your tax year.”

• If you do not receive your income evenly throughout the year or must begin making estimated payments in mid-year, you may be able to annualize your income.

  “If you do not receive your income evenly throughout the year or if you must begin making estimated payments in mid-year, you may be able to annualize your income.”

The form encourages electronic payment: online through MyTax Illinois (mytax.illinois.gov), which takes the payment from your checking or savings account and needs your IL-PIN; by credit card, where the card service provider charges a convenience fee; or by electronic funds transfer with Form EFT-1. If you pay by check or money order you complete a separate IL-1040-ES voucher for each payment, with your Social Security number(s), the tax year and “IL-1040-ES” on the payment, and mail it with the payment to the Illinois Department of Revenue, Springfield, IL 62736-0001, the address printed on the voucher.

• The Department encourages you to use MyTax Illinois, its free account management program, to make your payments online.

  “We encourage you to use MyTax Illinois, our free account management program, to make your payments online.”

• The credit card service provider will assess a convenience fee.

  “The credit card service provider will assess a convenience fee.”

• If you pay electronically, do not send the Department your payment voucher.

  “Note: If you pay electronically, do not send us your payment voucher.”

• Detach the voucher and enclose it with your payment.

  “Note: Detach the voucher, and enclose it with your payment.”

Official page: Illinois Department of Revenue: MyTax Illinois. Form: Form IL-1040-ES (Estimated Income Tax Payment for Individuals).

The 2026 form says only that a late-payment penalty may be assessed and points to Publication 103 for penalties and interest. Publication 105 gives the percentages below.

• You may be assessed a late estimated payment penalty if you do not pay the required estimated payments on time.

  “You may be assessed a late estimated payment penalty if you do not pay the required estimated payments on time.”

• For payments made 1 to 30 days late, the penalty is 2% of the tax due; for payments made 31 days or later, it is 10% of the tax due.

  “For payments made 1 to 30 days late, the penalty is 2% of the tax due; and for payments made 31 days or later, the penalty is 10% of the tax due.”

• The Department applies each payment to the earliest due date until that liability is paid unless you provide specific instructions to apply it to another period.

  “We will apply each payment to the earliest due date until that liability is paid unless you provide specific instructions to apply it to another period.”