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Last reviewed: October 18, 2026
Illinois estimated tax payments for 2026 are due April 15, June 15, September 15, 2026, and January 15, 2027, made through MyTax Illinois or with Form IL-1040-ES, and they are required when you expect your Illinois tax after withholding and credits to exceed $1,000. To calculate them, subtract $2,925 per exemption from your Illinois base income, multiply by 4.95%, subtract withholding and credits, and divide by four. Only the January installment is still ahead. The amount that keeps the penalty away is the smaller of 90% of your 2026 tax or 100% of your 2025 tax, and a short installment costs a flat 2% if you catch up within 30 days, 10% after that.
Key takeaways:
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Illinois uses the federal calendar, per the 2026 Form IL-1040-ES:
| Installment | Due date | Share of the year's required payment |
|---|---|---|
| 1 | April 15, 2026 (passed) | 25%, or the whole year at once |
| 2 | June 15, 2026 (passed) | 25% |
| 3 | September 15, 2026 (passed) | 25% |
| 4 | January 15, 2027 (a Friday) | 25% |
A due date on a weekend or holiday moves to the next business day, per IDOR's Publication 105. The dates match federal Form 1040-ES, and the estimated tax due-dates tool lists both calendars side by side.
Two Illinois rules shape the calendar. IDOR applies every payment to the earliest due date that is still short unless you tell it otherwise, so a late September check first fills the September hole. And Illinois has no early-filing shortcut for the fourth installment: 35 ILCS 5/804, the penalty statute, lists no exception for a return filed in January, unlike the federal rule. If you start owing estimates mid-year, the IL-1040-ES sends you to the annualized income method on Form IL-2210 instead of a catch-up schedule.
You must make Illinois estimated payments if you reasonably expect your 2026 Illinois tax to exceed $1,000 after subtracting Illinois withholding, pass-through withholding, and credits for tax paid to other states, Illinois property tax, K-12 education expenses, the Illinois EITC and Child Tax Credit, the pass-through entity tax credit, and Schedule 1299-C credits. IDOR adds that you will likely need estimates "if your income is either fully or partially exempt from Illinois withholding," which describes almost every freelancer, landlord, and partnership owner. Married couples who will file jointly figure the estimate on joint income.
Two groups are exempt by the form itself: people 65 or older who live permanently in a nursing home, and farmers, meaning at least two-thirds of total federal gross income comes from farming.
Three Illinois features shrink the group further:
Illinois estimated tax is one subtraction, one multiplication, and a division by four. The IL-1040-ES worksheet runs:
| Worksheet line | What goes there |
|---|---|
| 1 | Illinois base income you expect for 2026: federal AGI plus Illinois additions, minus subtractions such as retirement income |
| 2 | Exemption amount: $2,925 for you, $2,925 for a joint spouse, $2,925 per dependent, plus $1,000 each for age 65+ and legal blindness |
| 3 | Line 1 minus line 2: net income |
| 4 | Line 3 × 4.95% |
| 5–6 | Add any cannabis or gaming-licensee surcharge (rare) |
| 7 | Illinois withholding and pass-through withholding you expect |
| 8 | Expected credits: property tax, other states, K-12, EITC, Child Tax Credit, PTE tax credit, Schedule 1299-C |
| 10 | Estimated tax: line 6 minus lines 7 and 8. $1,000 or less means no payments |
| 11 | Line 10 ÷ 4, rounded to whole dollars: each installment |
The $2,925 exemption is new for 2026, up from $2,850 for 2025, per IDOR's Informational Bulletin FY 2026-15. The same bulletin repeats the income cap: no exemption allowance at all when federal AGI exceeds $500,000 on a joint return or $250,000 on any other return. Because Illinois starts from federal AGI, the deductible half of self-employment tax, self-employed health insurance, and SEP or solo 401(k) contributions all reduce Illinois income too.
Worked example. Junie, a freelance copywriter in Evanston (single, no dependents, no Illinois withholding), expects 2026 federal AGI of $92,925 after the half-of-self-employment-tax deduction, with no Illinois additions or subtractions.
| Step | Amount |
|---|---|
| Line 1: Illinois base income | $92,925 |
| Line 2: one exemption | −$2,925 |
| Line 3: net income | $90,000 |
| Line 4: tax at 4.95% | $4,455 |
| Lines 7–8: withholding and credits | $0 |
| Line 10: estimated tax (over $1,000, so payments are required) | $4,455 |
| Line 11: $4,455 ÷ 4 | $1,114 per installment |
Line 11 pays 100% of the year's estimate, which is what the IL-1040-ES recommends. The penalty-proof minimum can be lower, as the next section shows.
The retirement subtraction changes the math for older owners. Thaddeus, 63, consults from Naperville and expects federal AGI of $125,000: $58,000 of consulting income after the self-employment tax deduction, $45,000 of IRA withdrawals, and $22,000 of taxable Social Security. Illinois subtracts the $67,000 of IRA and Social Security income on line 5, leaving base income of $58,000 and Illinois tax of ($58,000 − $2,925) × 4.95% = $2,726.21. Without the subtraction the bill would be $6,042.71, so it saves him $3,316.50 and cuts his IL-1040-ES installments by more than half. His federal vouchers still carry tax on all $125,000, plus self-employment tax on the consulting profit.
IDOR does not charge the estimated tax penalty when each installment is paid on time and the four together reach the smaller of two amounts, under 35 ILCS 5/804(c) and the 2025 Form IL-2210 instructions:
| Option | Required total | Catch |
|---|---|---|
| Current year | 90% of your 2026 Illinois tax | Measured against the actual tax on your 2026 IL-1040 |
| Prior year | 100% of your 2025 Illinois tax | The 2025 return must cover 12 months and show a liability |
| Annualized income | 22.5%, 45%, 67.5%, and 90% of tax on annualized income | Form IL-2210, Step 6; annualize one quarter and you annualize all four |
Illinois never raises the prior-year anchor to 110%, the step the IRS adds under IRC §6654(d) once prior-year AGI tops $150,000.
Junie owed $3,960 of Illinois tax for 2025. Her safe harbor is the lesser of 90% × $4,455 = $4,009.50 or 100% × $3,960 = $3,960, which is $990 per installment. That is $124 a quarter less than the worksheet's $1,114. She settles the remaining $495 with her 2026 IL-1040 by April 15, 2027, penalty-free, because the prior-year anchor holds even if her income keeps climbing.
Interactive
What should each IL-1040-ES payment be?
Enter your expected 2026 Illinois base income (federal AGI plus Illinois additions, minus subtractions such as retirement income), your number of exemptions, Illinois withholding and credits, and your 2025 Illinois tax.
IL-1040-ES worksheet line 1.
You, your spouse if joint, and dependents.
W-2 withholding, PTE tax credit, other credits.
2025 IL-1040 tax after credits. Enter 0 if none.
Each of your four installments (penalty-proof minimum)
$990
Locked in by 100% of your 2025 tax. No penalty even if 2026 comes in higher.
2026 IL-1040-ES worksheet and 2025 IL-2210. Tax = (base income - $2,925 per exemption) x 4.95%. Enter 0 exemptions if federal AGI is over $250,000 ($500,000 joint). Safe harbor: the lesser of 90% of 2026 tax or 100% of 2025 tax; Illinois has no 110% tier. No estimates are required when tax after withholding and credits is $1,000 or less. Late installments cost a flat 2% (1 to 30 days late) or 10% (31 days or more).
Add federal and self-employment taxIDOR's payment page takes estimated payments three ways:
Do not mail the voucher if you pay electronically. By mail, enter the payment in whole dollars on the voucher, make the check payable to the Illinois Department of Revenue, print your Social Security number, the tax year, and "IL-1040-ES" on the check, and send both to Illinois Department of Revenue, Springfield, IL 62736-0001. On a joint return, list both Social Security numbers in the order they will appear on your IL-1040.
To check what IDOR has credited, use the "Look Up Your Estimated Payments, Extension Payments, and Credits Carried Forward" link on IDOR's Individuals page, which opens the inquiry in MyTax Illinois. IDOR's taxpayer line, 1-800-732-8866, also reads estimated payment information through an automated menu. A 2025 overpayment you credited forward counts from the first installment if you elected it by the extended due date of the 2025 return; a later election counts from the day you made it.
Illinois charges a flat late-payment penalty on a short installment, based only on how many days late the money arrives. Publication 103 and Form IL-2210 set two brackets: 2% of the amount paid 1 to 30 days after the due date, and 10% of anything paid 31 or more days late or never paid. Suppose Junie skips her $990 September 15 installment:
| Catch-up date | Days late | Penalty |
|---|---|---|
| October 15, 2026 | 30 | $19.80 (2%) |
| October 16, 2026 | 31 | $99.00 (10%) |
| April 15, 2027, with the return | 212 | $99.00 (10%) |
The 31st day is a cliff: one day costs her $79.20. After that, waiting longer costs nothing more, which is the opposite of the federal penalty in our estimated tax penalty guide, where interest grows every day. Building Jupid, I've seen plenty of owners treat a missed quarter as a write-off until April; in Illinois, the first 30 days are the cheapest window to fix it.
You do not have to compute the penalty. The IL-2210 instructions let you leave line 34 of the IL-1040 blank, skip the form, and let IDOR bill you. You must file it only to annualize income or to use actual withholding dates. No penalty applies at all if any of these is true:
Tax still unpaid when the April 15, 2027 return is due is a separate matter: it draws the same 2% or 10% late-payment penalty for unpaid tax plus interest, which IDOR's interest rate page shows at 7% for January 1, 2025 through December 31, 2026.
Illinois lets a partnership (other than a publicly traded one) or an S corporation elect each year to pay a pass-through entity tax of 4.95% of its net income, on Form IL-1065 or IL-1120-ST, per IDOR's Publication 129. Each partner or shareholder then claims a credit equal to 4.95% of their distributive share, and the IL-1040-ES worksheet subtracts that credit on line 8, so an owner whose entity elected may owe little or nothing on personal vouchers. An electing entity makes its own estimated payments once its PTE tax is expected to exceed $500 (Publication 105). Public Act 104-0453 removed the tax's expiration date, and sole proprietors and single-member LLCs cannot elect. The federal reason owners elect is covered in our SALT deduction guide.
Illinois estimated payments are deductible as state income taxes on federal Schedule A in the year you pay them, per Treasury Regulation §1.164-1, so Junie's January 15, 2027 installment is a 2027 federal deduction. Itemizers with room under the SALT cap in IRC §164 can pay it in December to pull the deduction into 2026; an early payment still counts for the January installment.
A September 15 installment paid October 16 costs five times the penalty of one paid October 15. If you are short, pay inside the 30-day window even if the amount is partial.
Federal AGI over $250,000 ($500,000 joint) removes the exemption allowance entirely. Leaving $2,925 on line 2 understates the estimate by $144.79 per exemption.
IRA withdrawals and taxable Social Security come off on line 5 of the IL-1040. A retiree who multiplies federal AGI by 4.95% prepays Illinois tax that will never be owed, $3,316.50 a year in Thaddeus's case.
Illinois's prior-year anchor is 100% at every income level. Mirroring the federal 110% rule prepays a tenth of last year's Illinois tax for no extra protection.
Illinois's 4.95% math takes a minute once you know your base income; the work is knowing it before January 15 instead of in March. Jupid connects to your bank accounts and categorizes income and expenses with 95.9% accuracy, so client payments, retirement transfers, and personal spending stay apart all year. Ask the AI accountant in WhatsApp or iMessage what your business has earned so far in 2026, and you have line 1 of the IL-1040-ES worksheet in the same conversation. Try Jupid.
This guide is for general educational purposes and does not constitute tax, legal, or accounting advice. It reflects the 2026 IL-1040-ES (R-09/26), the 2025 IL-2210 and IL-1040 instructions, 35 ILCS 5/804, and Illinois Department of Revenue guidance as reviewed on October 6, 2026; Illinois resets its interest rate every January 1 and July 1. For advice specific to your situation, consult a qualified tax professional or the Illinois Department of Revenue at tax.illinois.gov.
CEO & Co-Founder
Fintech CEO with 10+ years building accounting and financial technology products. Previously co-founded and scaled an AI-powered accounting platform to $30M revenue and 100K+ business users, achieving 30,000 customers per accountant through automation — recognized by CNBC as a top fintech company. Holds a Master's in Management Information Systems. At Jupid, he leads the development of AI-native bookkeeping, tax, and compliance tools designed for freelancers and small business owners.
NJ estimated tax payments 2026: NJ-1040-ES due dates, the $400 trigger, an 80%/100% safe harbor with no 110% tier, 1.4% to 10.75% rates, 10% interest.
NC estimated tax payments 2026: NC-40 due dates, the $1,000 trigger, a 90%/100% safe harbor with no 110% tier, the 3.99% rate, and 7% interest.
Missouri estimated tax payments 2026: MO-1040ES due dates, the $100 trigger, a 90%/100% safe harbor with no 110% tier, 4.7% top rate, capital gains subtraction.
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