Child Support in Illinois: How Much Will You Owe?

Quick answer: it depends on both parents' incomes, how many children you have, and the parenting schedule. The calculator on this page turns those numbers into a real guideline estimate in about a minute. It is an educational estimate, not legal advice, and the judge always sets the final amount. FamilyCourtHelp.com is a self-help resource, not a law firm.

Wondering how much child support you will owe or receive in Illinois? The state uses one formula everywhere, so the same math applies in every county. This page explains how it works, lets you run a live estimate, and links to a dedicated page for each county at the bottom.

Illinois follows the Income Shares model under 750 ILCS 5/505. The court combines both parents' monthly gross incomes, looks up the basic support obligation on the state's guideline schedule for that income level and number of children, then prorates the obligation between the parents according to each parent's percentage share of the combined income.

What counts as income? Illinois runs the formula on income after certain allowed deductions are taken out. Net income, gross income from any source minus federal and state income taxes, FICA, mandatory retirement, union dues, dependent and individual health insurance, prior obligations of support, and reasonable business expenses.

Parenting time matters directly in Illinois: the number of overnights each parent has changes the math itself. Illinois uses the Income Shares model, so the basic obligation is first set by combining both parents' incomes. Parenting time changes the math only when each parent has at least 146 overnights per year, which is 40 percent or more of the year. At that point a shared physical care formula applies, which can lower the paying parent's number. Below 146 overnights, the standard guideline calculation under 750 ILCS 5/505 controls and extra parenting time does not automatically reduce support.

When does it end? Illinois child support generally ends at age 18 but continues through high school not past age 19. Non-minor support for college expenses can be ordered under 750 ILCS 5/513.

Can the amount change later? File a petition to modify in the circuit court that issued the order, or request administrative review through Illinois DCSS. A 20% variance is commonly cited as a benchmark.

If payments fall behind, Illinois has real enforcement tools. Illinois DCSS uses immediate income withholding, tax intercept, license suspension, lien filings, and contempt referrals. Non-payment can also trigger driver's license suspension and credit reporting.

Child support cases in Illinois are generally handled through the state's Circuit Court, and Illinois Department of Healthcare and Family Services, Division of Child Support Services runs the state's child support services program. Forms and local practice can vary, so confirm the current details with your local court or the agency.

The calculator on this page is the same live engine behind our full Child Support Calculator. Enter both incomes, the number of children, and the overnight split, and the estimate updates instantly. The full calculator page adds extras like health insurance, child care costs, and saved scenarios.

Bottom line for Illinois: the guideline number comes from incomes, children, and parenting time. Run the estimate on this page, keep your paperwork honest and complete, and let the court confirm the final amount.

Frequently asked questions

How much child support will I owe in Illinois?

There is no flat amount. Illinois uses the Income Shares model under 750 ILCS 5/505, so the number depends on both parents' incomes, the number of children, and the parenting schedule. The calculator on this page gives you a guideline estimate, and the court sets the final amount.

When does child support end in Illinois?

Age 18, or until graduation from high school not past age 19, whichever is later.

Can the child support amount be changed later in Illinois?

Usually yes, when circumstances change enough. A substantial change in circumstances; a 20% variance between the order and a new guideline calculation is commonly cited as a benchmark.

Who handles child support cases in Illinois?

Cases are generally heard in the state's Circuit Court, and Illinois Department of Healthcare and Family Services, Division of Child Support Services handles services like locating parents, establishing orders, and collecting payments.