Illinois Child Support Calculator
Estimate your monthly child support obligation under 750 ILCS 5/505. Enter your numbers below for an instant estimate with a step-by-step breakdown and statute citations.
What You'll Need
Gather these four figures first for an accurate Illinois estimate:
- Each parent's gross monthly income — recent pay stubs and last year's tax return are the best source.
- Number of children covered by the order.
- Parenting time — roughly how many overnights per year the child spends with each parent.
- Monthly health insurance and childcare costs for the children.
Illinois Child Support Calculator
This state uses the Income Shares model, which considers both parents' income to determine a combined obligation, then splits it proportionally.
Based on 750 ILCS 5/505 · Effective January 1, 2026
Enter income details to see your estimate
How Illinois Calculates Child Support
Illinois determines child support using the Income Shares Model, the standard set out in 750 ILCS 5/505. Under this model, the incomes of both parents are combined to estimate what they would have spent on the children if the family were intact, and that total obligation is then divided between them in proportion to each parent's share of the combined income.
The calculator above applies that formula to the income and expense figures you enter and shows each step of the math, so you can see exactly how the estimate is built. Because every order ultimately runs through a judge, the guideline figure is a starting point rather than a guaranteed result — the sections below explain what goes into it and where real orders can differ.
Key Rules Behind the Illinois Formula
- Illinois switched from the Percentage of Income model to the Income Shares model on July 1, 2017, bringing it in line with the majority of U.S. states.
- Under the Income Shares model, both parents' net incomes are combined to determine the basic child support obligation from a statutory schedule (750 ILCS 5/505).
- A shared parenting adjustment applies when the non-custodial parent has 146 or more overnights per year (40% of the time), using a formula that accounts for duplicated expenses in both households.
- Health insurance premiums for the children and work-related or education-related childcare costs are added to the basic obligation and divided proportionally between parents.
- Illinois courts may deviate from the guidelines based on the best interests of the child, including factors such as extraordinary medical expenses, educational needs, and the standard of living the child would have enjoyed had the parents remained together.
What Counts as Income
Child support guidelines are built on each parent's income, so the figure you enter matters more than any other input. Most states start from a broad definition of gross income that includes wages, salary, tips, commissions, bonuses, self-employment earnings, and many forms of government benefits, then subtract specific deductions to reach the income the formula actually uses.
Illinois's rules under 750 ILCS 5/505 spell out which deductions apply and whether the formula runs on gross or net income. The calculator's field labels tell you which figure to enter; when in doubt, use your most recent pay stubs and tax return, and confirm the details in the Illinois child support laws guide.
How to Establish a Child Support Order in Illinois
A child support obligation becomes enforceable only once a court or the state child support agency issues an order. Either parent can request one, and in Illinois, as in every state, the local child support agency that operates under the federal Title IV-D program can open a case, locate the other parent, establish paternity if needed, and ask the court to set support using the guideline formula.
When you apply, expect to provide proof of income for both parents, the child's information, and details about health insurance and childcare costs — the same inputs this calculator uses. Running your numbers here first gives you a realistic idea of the order amount before you file.
How Illinois Calculates Child Support
- •Illinois switched from the Percentage of Income model to the Income Shares model on July 1, 2017, bringing it in line with the majority of U.S. states.
- •Under the Income Shares model, both parents' net incomes are combined to determine the basic child support obligation from a statutory schedule (750 ILCS 5/505).
- •A shared parenting adjustment applies when the non-custodial parent has 146 or more overnights per year (40% of the time), using a formula that accounts for duplicated expenses in both households.
- •Health insurance premiums for the children and work-related or education-related childcare costs are added to the basic obligation and divided proportionally between parents.
- •Illinois courts may deviate from the guidelines based on the best interests of the child, including factors such as extraordinary medical expenses, educational needs, and the standard of living the child would have enjoyed had the parents remained together.
What Is the Average Child Support Payment in Illinois?
Estimated Average Monthly Payment
$1,207/month
Estimated Annual Total
$14,484/year
Illinois does not publish an official “average” child support payment. This estimate was calculated using the Illinois guideline formula above with median income data from the U.S. Census Bureau, American Community Survey (ACS) 2024 — Illinois Median Earnings. Your actual amount will differ — use the calculator above with your own numbers for a personalized estimate.
Assumptions used in this estimate
- •Obligor net monthly income of $3,900 (Illinois median full-time earnings after taxes, Census ACS 2024)
- •Obligee net monthly income of $3,100
- •2 children
- •$200/month for children's health insurance
- •No childcare costs; 52 overnights/year with obligor (below shared parenting threshold)
Data year: 2024
Important Legal Disclaimer
This calculator provides an estimate only based on Illinois's child support guidelines. Actual court-ordered amounts may differ based on factors not captured here, including special needs, shared custody arrangements, travel costs, and judicial discretion.
This is not legal advice. Consult a family law attorney for guidance specific to your situation.
How to Modify a Illinois Child Support Order
Child support orders are not permanent. Illinois courts can revisit an order when there has been a substantial change in circumstances — for example, a significant change in either parent's income, a change in custody or parenting time, or a meaningful change in the child's needs. Federal rules also entitle parents in IV-D cases to request a review periodically (often about every three years) even without a major change.
To estimate a new amount, re-run the calculator with the updated figures. If the guideline result is meaningfully different from your current order, that gap is often what supports a modification request — though only a court can actually change the order.
How Child Support Is Enforced in Illinois
Once an order is in place, Illinois has strong tools to collect it. The most common is income withholding: federal law requires most new orders to be paid through automatic wage garnishment, so payments are deducted from the paying parent's paycheck. When payments fall behind, enforcement can escalate to intercepting tax refunds, suspending driver's or professional licenses, placing liens on property, reporting the debt to credit bureaus, and, in serious cases, contempt-of-court proceedings.
Interest and penalties can accrue on unpaid support, so an order that goes unaddressed tends to grow rather than disappear. If your circumstances have changed, seeking a modification through the court is almost always better than simply paying less than the order requires.
Frequently Asked Questions
Is this Illinois child support calculator accurate?
It applies the official Illinois guideline formula from 750 ILCS 5/505 to the numbers you enter, so it gives a close estimate of a typical guideline order. It is not an official court calculation — a judge can order a different amount based on the specific facts of your case.
Can a judge order a different amount than the calculator shows?
Yes. The guideline figure is a presumptive starting point, but Illinois courts can deviate up or down when the standard amount would be unfair — for example, because of extraordinary medical or educational expenses, a child's special needs, or other obligations. The order the judge signs controls.
What income do I enter into the Illinois calculator?
Use the figures described by each field's label — generally your regular income from work and other sources. Illinois's guidelines define exactly which income counts and which deductions apply, so your most recent pay stubs and tax return are the best source for accurate numbers.
Is child support taxable in Illinois?
No. Under federal tax law, child support is not taxable income for the parent who receives it and is not tax-deductible for the parent who pays it. This is different from spousal support and does not change from state to state.
How long does child support last in Illinois?
In most cases child support continues until the child reaches the age of majority or finishes high school, but orders can extend longer — for instance, for a child with a disability. Check the Illinois child support laws guide for the specific rules that apply to your situation.
Disclaimer
This calculator provides estimates only and is not a substitute for legal advice. The actual amount ordered by a Illinois court may differ based on factors including but not limited to: the special needs of the child, travel expenses for visitation, extraordinary educational or medical expenses, the parents' other support obligations, and the court's discretion to deviate from the guidelines. For advice about your specific situation, consult a licensed Illinois family law attorney.
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