Form IL-W-4 and Illinois Withholding Explained
Form IL-W-4 tells your employer how much Illinois income tax to hold back from each paycheck. It works on allowances — unlike the modern federal W-4 — and getting it wrong is the most common reason an Illinois paycheck looks different from what people expect.
Two forms, two systems
Every Illinois employee completes two withholding certificates, and they do not resemble each other.
| Federal Form W-4 | Illinois Form IL-W-4 | |
|---|---|---|
| System | Filing status, dollar credits, adjustments | Allowances |
| Allowances used? | No — removed in the 2020 redesign | Yes |
| Filing status matters? | Yes, it selects the rate schedule | No — 4.95% applies regardless |
| Dependents | Step 3, a dollar credit of $2,200 per child under 17 | Line 1, an allowance sheltering $2,925 of wages |
| Extra withholding | Step 4(c), per pay period | Line 3, per pay period |
| Exempt claim | Written below Step 4(c) | Line 7 |
Because Illinois has a flat rate, your IL-W-4 has a much smaller effect on your paycheck than your federal W-4 does. Each Illinois allowance is worth about $145 of tax across a whole year. Each federal dependent credit is worth $2,200. If your withholding is badly wrong, the federal form is almost always the culprit.
Form IL-W-4, line by line
Line 1 — basic allowances
These are tied to the Illinois personal exemption, worth $2,925 each in 2026. Claim one for yourself unless someone else claims you as a dependent, one for a spouse who is not claiming an allowance on their own IL-W-4, and one for each dependent you will claim on Form IL-1040.
One Line 1 allowance shelters $2,925 of wages from the 4.95% rate — $144.79 of Illinois tax across the year, or about $5.57 per bi-weekly paycheck. A family of four claiming four allowances saves $579.15 a year.
Line 2 — additional allowances
Worth $1,000 each. Claim one if you are 65 or older, one if you are legally blind, and the same again for a spouse on a joint return where applicable. Each is worth $49.50 of Illinois tax a year.
Line 3 — additional withholding
A flat dollar amount you want withheld from each paycheck on top of the calculated figure. Useful when you have income that Illinois will tax but that carries no withholding — freelance work, rental income, investment income, or a second job.
Line 7 — exempt status
Only for someone who had no Illinois tax liability last year and expects none this year, or who qualifies under the Military Spouses Residency Relief Act. The election must be renewed annually. If you claim exempt and end up owing, penalties and interest follow.
How your allowances turn into withholding
The employer prorates the annual allowance value across your pay periods. On a bi-weekly cycle, two Line 1 allowances are worth $5,850 a year, or $225 per period.
| Allowances claimed | Sheltered per year | Illinois tax per year | Per bi-weekly paycheck |
|---|---|---|---|
| 0 | $0 | $2,970.00 | $114.23 |
| 1 | $2,925 | $2,825.21 | $108.66 |
| 2 | $5,850 | $2,680.43 | $103.09 |
| 3 | $8,775 | $2,535.64 | $97.52 |
| 4 | $11,700 | $2,390.85 | $91.96 |
The spread from zero to four allowances is $579 a year — real money, but modest compared with what the federal form can move. See the combined effect on the Illinois paycheck calculator, which takes both forms as input.
The federal Form W-4, which matters more
The 2020 redesign removed allowances and replaced them with five steps. Three of them do almost all the work:
- Step 1 — filing status. Selects the rate schedule. Married filing jointly uses brackets roughly twice as wide as single.
- Step 2 — multiple jobs. Ticking the box roughly doubles the rate applied to the job that ticks it, on the assumption a second income is stacking on top. Both spouses should tick it, or neither.
- Step 3 — dependents. A dollar credit: $2,200 per qualifying child under 17 for 2026, $500 per other dependent. This is subtracted directly from annual withholding, so it is the single most powerful field on the form.
- Step 4 — adjustments. (a) other income you want covered, (b) deductions above the standard deduction, (c) extra withholding per pay period.
When both spouses work and neither ticks the Step 2 box, each employer withholds as though its salary were the household's only income. Both are individually correct and the couple is collectively under-withheld — which is the most common cause of an unexpected April bill for dual-income households. Ticking the box on both W-4s, or using the Step 2(b) worksheet, fixes it.
Working across state lines
| Situation | What to file | Who taxes the wages |
|---|---|---|
| Live and work in Illinois | W-4 and IL-W-4 | Illinois |
| Live in IA, KY, MI or WI, work in Illinois | Form IL-W-5-NR | Your home state |
| Live in Illinois, work in IA, KY, MI or WI | The other state's non-residence form, plus IL-W-4 | Illinois |
| Live in Illinois, work in Indiana or Missouri | Both states' forms | The work state, with an Illinois credit on Schedule CR |
| Live in Illinois, work remotely for an out-of-state employer | W-4 and IL-W-4 | Illinois — wages are sourced where the work is performed |
A withholding check worth doing once a year
- Ask HR for copies of the Form W-4 and Form IL-W-4 currently on file. What you remember submitting and what is on file are frequently different.
- Confirm the filing status matches how you will actually file.
- Check the Step 2 box against reality — two jobs, or a working spouse.
- Confirm Step 3 reflects the children and dependents you will claim, at $2,200 and $500.
- Count your IL-W-4 allowances against the worksheet.
- Run the numbers through the paycheck calculator and compare with a recent pay stub.
- If the year-to-date figure is off track, submit a corrected form. There is no limit on how often you may do so.
People also ask about the IL-W-4
No — they are separate forms and they work differently. The federal Form W-4 was redesigned in 2020 and no longer uses allowances at all; it asks for filing status, dependent credit amounts in dollars, and optional adjustments. The Illinois Form IL-W-4 still uses the old-style allowance system, where each allowance shelters a fixed amount of wages. You need to complete both, and completing one does not populate the other.
The worksheet gives the honest answer for most people: one basic allowance for yourself unless someone else claims you as a dependent, one for a spouse who is not claiming themselves elsewhere, and one for each dependent you will claim on your return. Add Line 2 allowances if you or your spouse are 65 or older or legally blind. Claiming more than you are entitled to means under-withholding and a bill in April; claiming fewer means a larger refund and a smaller paycheck all year.
Illinois withholds 4.95% of every dollar of wages with no shelter at all. On a $60,000 salary that is $2,970 a year, versus $2,680.43 if you claimed two allowances — a difference of about $290 across the year, or $11 a paycheck on a bi-weekly cycle. Claiming zero is a deliberate over-withholding strategy some people use to build a forced refund; it is not an error, just an expensive habit.
Your employer must withhold as though you claimed zero allowances — the maximum Illinois withholding. Illinois tax is still withheld either way, so failing to file the form costs you money in each paycheck without any offsetting benefit. If you have never submitted one, ask HR; many employers keep the form on file from your first day and never revisit it.
Three groups, mainly. Residents of Iowa, Kentucky, Michigan or Wisconsin who work in Illinois file Form IL-W-5-NR and pay tax to their home state instead. Certain military spouses qualify under the Military Spouses Residency Relief Act. And a taxpayer who had no Illinois tax liability last year and expects none this year may claim exempt on Line 7 of Form IL-W-4 — an election that must be renewed each year and is only appropriate if it is genuinely true.
If you live in a reciprocal state — Iowa, Kentucky, Michigan or Wisconsin — do not complete an IL-W-4 for exemption purposes. File Form IL-W-5-NR, Employee's Statement of Non-residence in Illinois, with your employer. That stops Illinois withholding entirely and you pay tax to your home state. If you live in any other state and work in Illinois, complete a normal IL-W-4 and Illinois tax is withheld on your Illinois-source wages.
Whenever the facts change: marriage or divorce, a new baby or a dependent you can no longer claim, turning 65, a change in your spouse's employment, or moving into or out of Illinois. You may submit a new IL-W-4 at any time and as often as you like. Your employer must put it into effect no later than the start of the first pay period ending on or after the 30th day after you hand it in.
Yes. Line 3 of Form IL-W-4 lets you specify an additional flat dollar amount per pay period. It is a useful tool if you have self-employment income, investment income or a second job that produces Illinois tax with no withholding attached — adding to Line 3 spreads the liability across the year rather than leaving it to a single payment in April. The federal equivalent is Step 4(c) of Form W-4.
Sources
- IDOR — Booklet IL-700-T, 2026 withholding tables and IL-W-4 allowance values
- IDOR — withholding tax forms, including IL-W-4 and IL-W-5-NR
- IRS — About Form W-4
- IRS Tax Withholding Estimator
General guidance only. How many allowances you may legitimately claim depends on your own tax situation. Consult a tax professional if you are unsure, and never claim exempt status unless it is genuinely true.