Illinois Child Support Calculator

Estimate Illinois child support for 2026 using the Income Shares guideline model under 750 ILCS 5/505. Enter both parents' incomes and the parenting-time split to see what you may owe or receive.

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.

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.

Under 750 ILCS 5/505, the cost of the child's health insurance premium is treated as an add-on to the basic support obligation. The premium paid for the children is divided between the parents in proportion to each parent's share of the combined income, the same way the basic obligation is split. The parent who actually pays the premium generally receives credit for the other parent's share, so the final order reflects who carries the coverage.

Work-related and education-related child care is treated as an add-on in Illinois, not part of the base guideline figure. Reasonable child care that lets a parent work or attend school is added to the basic obligation and then split between the parents in proportion to their incomes. Because daycare can change a lot over time, keep receipts and provider statements so the actual cost can be documented and divided correctly in the order.

An Illinois judge starts from the guideline amount under 750 ILCS 5/505 and that figure is presumed correct. A court may deviate up or down if applying the guideline would be unfair given the child's needs, the parents' resources, or the child's standard of living. The parent asking for a different number carries the burden of showing why a deviation is justified, and the judge must put specific written reasons for any deviation in the order.

Frequently asked questions

How is child support calculated in Illinois?

Illinois uses the Income Shares model under 750 ILCS 5/505. The court combines both parents' monthly net incomes, then looks up the basic support obligation on the state guideline schedule for that combined income and the number of children. That obligation is divided between the parents in proportion to each parent's share of the combined income, and the parent who does not have the majority of parenting time typically pays their share to the other. Add-ons like health insurance and work-related child care are layered on top. The on-page calculator gives an estimate only, not legal advice, and the official worksheet and your court order control the final number.

What is the official Illinois child support worksheet and does it control my case?

Yes. Illinois requires an official guideline worksheet that walks through each parent's net income, the combined basic obligation from the state schedule, the proportional split, and the add-ons. The approved circuit court forms are published through the Illinois Courts forms library, and the court relies on that completed worksheet, not an online estimate, to set the order. Any calculator on this page is a planning tool to help you understand the math. The controlling document is the official worksheet filed in your case, reviewed by the judge under 750 ILCS 5/505. When the numbers matter, confirm them on the official form or with a licensed Illinois attorney.

What counts as income for Illinois child support, and how are bonuses or self-employment handled?

Illinois bases support on net income, which is gross income from any source minus federal and state income taxes, FICA, mandatory retirement contributions, union dues, health insurance for the parent and dependents, prior support obligations, and reasonable business expenses. Because income comes from any source, bonuses, overtime, commissions, and self-employment earnings count. For a self-employed parent, the court looks at gross receipts minus legitimate, ordinary business expenses, and personal expenses run through a business can be added back. Irregular pay like a yearly bonus may be averaged. This page estimates only; the official worksheet under 750 ILCS 5/505 and the court decide what income is included.

Does sharing parenting time 50/50 lower child support in Illinois?

It can, but only once a threshold is met. Illinois applies a shared physical care formula when each parent has at least 146 overnights with the child per year, which is 40 percent or more of the time. At or above that point the standard calculation is replaced by the shared care formula, which accounts for both households and often reduces the paying parent's amount. If one parent has fewer than 146 overnights, the regular Income Shares guideline under 750 ILCS 5/505 applies and the extra time does not automatically change the number. The calculator here is an estimate; the official worksheet and judge decide.

What happens to unpaid Illinois child support, and how is it enforced?

Past-due support, called arrears, does not go away on its own and generally cannot be wiped out retroactively. The Illinois Department of Healthcare and Family Services, Division of Child Support Services, enforces orders using immediate income withholding, state and federal tax refund intercepts, license suspension, liens, and contempt referrals to the court. Non-payment can also trigger driver's license suspension and credit reporting. Interest can accrue on overdue amounts. If you owe arrears or are owed them, contact Illinois DCSS at hfs.illinois.gov, and treat any figure on this page as an estimate rather than a legal calculation of what is owed.

When does child support end in Illinois?

Illinois child support generally ends when the child turns 18. If the child is still in high school at 18, support continues until graduation, but not past age 19, whichever comes later. That means the obligation often runs slightly past the 18th birthday for a student finishing school. Separately, a court can order non-minor support for college and related expenses under 750 ILCS 5/513, which is handled apart from the basic guideline. Support does not stop automatically in every situation, so confirm the end date in your order. This page is an estimate, not legal advice; check the official rules or an attorney.

Can I change an Illinois child support order if my income changes?

Yes. You file a petition to modify in the circuit court that issued the order, or you can request an administrative review through Illinois DCSS. The legal standard is a substantial change in circumstances, such as a major shift in either parent's income, a new parenting schedule, or a change in the child's needs. A 20 percent difference between the current order and a fresh guideline calculation under 750 ILCS 5/505 is commonly cited as a benchmark for modification. Support usually changes only from the filing date forward, not retroactively, so file promptly. Use this calculator to estimate a new figure, then confirm it on the official worksheet.