How to Fill Out the Illinois IL-W-4 Withholding Allowance Certificate

To fill out the Illinois IL-W-4, complete the allowance worksheet on the back of the form, carry your totals to Lines 1 and 2 on the front, sign it, and hand it to your employer’s payroll or HR department. Illinois taxes wages at a flat 4.95 percent, so the allowances you claim decide how much of each paycheck escapes withholding, not which bracket applies to you.¹ Each allowance shelters $2,925 of annual income for the 2026 tax year.²

Gather These Before You Start

You need three things: your Social Security number, a count of the dependents you plan to claim on your federal return, and your most recent federal Form W-4 (one number from it feeds the additional-allowances step). If you own Illinois property and pay real estate taxes, have that dollar amount handy too, because it can raise your allowances.³

The current form is a single page with the worksheet on the back, available from the Illinois Department of Revenue at tax.illinois.gov.⁴

Step 1 of the Worksheet: Basic Personal Allowances

Check the boxes that apply: “No one else can claim me as a dependent” and “I can claim my spouse as a dependent.” On Line 1, write the number of boxes you checked. On Line 2, write the number of other dependents you will claim on your tax return. Add the two together on Line 3. That total is your basic personal allowances.⁴

A single person with no dependents who is not claimed on anyone else’s return enters “1” on Line 1, “0” on Line 2, and “1” on Line 3. A married employee claiming a spouse and two children enters “2,” then “2,” for a Line 3 total of “4.”

Step 2 of the Worksheet: Additional Allowances

This step covers what Step 1 misses. Check any of these that apply to you: you are 65 or older, you are legally blind, your spouse is 65 or older, your spouse is legally blind. Put the count on Line 5. Each of those situations adds a $1,000 exemption.²

On Line 6, enter the amount from Line 4 of the Deductions Worksheet on your federal Form W-4, plus any additional Illinois subtractions. The common Illinois subtraction is the Illinois property taxes you paid during the year. Divide Line 6 by $1,000, round to the nearest whole number, and put the result on Line 7. Add Lines 5 and 7 for your total additional allowances on Line 8.⁴

If you paid $6,400 in Illinois property taxes and have no other subtractions, Line 6 is 6,400. Divide by 1,000 to get 6.4, round to 6, and put 6 on Line 7.

The Front of the Form

Fill in your name, Social Security number, and address at the top, then complete three numbered lines.

Line 1 is your total allowances: Line 3 plus Line 8 from the worksheet. You do not have to claim every allowance you qualify for. Claiming fewer means more tax comes out of each paycheck and less risk of a balance due at filing.

Line 2 is any extra dollar amount you want withheld each pay period. This helps if you have a second job, freelance income, or investment income your employer doesn’t see.

Line 3 is the exempt box, and you check it only if you qualify (see below). If you check it, leave Lines 1 and 2 blank.

Sign and date the form. An unsigned or incomplete IL-W-4 counts as no form at all, and your employer will withhold on your full compensation with no allowances. Give the completed form to your employer; do not mail it to the Illinois Department of Revenue.⁴ Keep a copy so you can check that your paycheck matches what you requested. Changes usually take one or two pay cycles to appear.

Claiming Exempt on Line 3

If you expect to owe no Illinois income tax for the year, check the exempt box on Line 3 and leave Lines 1 and 2 blank. Your employer will withhold nothing for state tax.⁴

One catch: your employer must disregard an IL-W-4 claiming exempt unless you have also filed a federal Form W-4 claiming exemption from federal withholding. Owing no federal tax does not automatically mean you owe no Illinois tax, so check both before claiming exempt for Illinois.⁴

When to File a New Form

File your first IL-W-4 on or before your first day of work. After that, you can file a new one any time your allowances go up, such as after having a child or buying a home with deductible property taxes.⁴

If your allowances go down, you must file a new form within 10 days. The instructions carve out one exception: the death of a spouse or dependent does not by itself trigger the 10-day deadline.⁴

If you expect to owe more than $1,000 in Illinois income tax after all withholding and credits, you could face an underpayment penalty at filing, so keeping the form current matters.⁵

Higher Incomes: Watch the Exemption Phaseout

The worksheet lets you claim allowances freely, but your actual personal exemption on your return can drop to zero at higher incomes. For the 2026 tax year, the exemption is disallowed entirely when federal adjusted gross income exceeds $500,000 for joint filers or $250,000 for other filing statuses.²

If your income is in that range, claiming a full set of allowances will leave you under-withheld. Reduce the number on Line 1, or add extra withholding on Line 2, to avoid a large balance at filing.

If You Live in Iowa, Kentucky, Michigan, or Wisconsin

Illinois has reciprocal agreements with those four states. If you live in one of them and commute to an Illinois job, you do not owe Illinois income tax on your wages, and you should not file an IL-W-4. File Form IL-W-5-NR (Employee’s Statement of Nonresidence in Illinois) with your employer instead.⁶ Non-residents from any other state file a regular IL-W-4.

1
Illinois Department of Revenue. Illinois Withholding Tax Tables
2
Illinois Department of Revenue. What Is the Illinois Personal Exemption Allowance?
3
Illinois General Assembly. 35 ILCS 5/702 – Amount Exempt From Withholding
4
Illinois Department of Revenue. Form IL-W-4 Employee’s and Other Payee’s Illinois Withholding Allowance Certificate and Instructions
5
Illinois Department of Revenue. Pub-105, Illinois Estimated Payments Requirements for Individuals and Businesses
6
Illinois Department of Revenue. Employee’s Statement of Nonresidence in Illinois