Estimate Illinois child support using the Income Shares Model. Free, private, and updated for 2026.
Legal Disclaimer
These calculators provide estimates for educational purposes only. Child support and family law calculations vary significantly by state, judge, and individual circumstances. Results are not legal advice and do not create an attorney-client relationship. Consult a licensed family law attorney in Illinois for advice specific to your situation.
Illinois uses the Income Shares Model to determine child support obligations. Illinois uses the Income Shares model since 2017, calculating support based on both parents' net monthly incomes (after taxes). Illinois has a detailed schedule of basic child support obligations and applies parenting time adjustments for non-custodial parents with 146+ overnights per year.
Illinois applies a 25% adjustment to guideline support when the non-custodial parent has 146-182 overnights. For 50/50 custody (183 overnights), Illinois uses the offset method. Illinois requires income withholding orders in all child support cases.
Illinois provides an online child support calculator through the Illinois Department of Healthcare and Family Services at childsupportillinois.com.
Alex earns $5,500/month gross income. Jordan earns $3,200/month. They have 2 children in Illinois. Alex has primary custody; Jordan has standard visitation (every other weekend, approximately 73 overnights/year).
This example uses approximate calculations. Actual Illinois child support requires the official Income Shares Model worksheet or software and should be verified with a licensed family law attorney or the court.
Both Parents' Income
Illinois's Income Shares Model combines both parents' incomes to determine the total family resources available for the children. A higher combined income results in higher support — reflecting the idea that children should benefit from the family's overall financial resources regardless of which parent they primarily reside with.
Custody and Parenting Time
Illinois adjusts child support based on the amount of parenting time each parent has. More overnight time with the paying parent generally reduces the support obligation — reflecting that the paying parent directly absorbs the children's costs during their parenting time. Illinois applies a 25% adjustment to guideline support when the non-custodial parent has 146-182 overnights.
Health Insurance and Childcare
Health insurance premiums for the children and work-related childcare costs are added to the basic child support obligation in Illinois. The cost is typically split proportionally based on each parent's share of combined income. These add-ons can significantly increase the total support obligation, particularly in cases with high childcare or health insurance costs.
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Illinois uses the Income Shares Model to calculate child support. Illinois uses the Income Shares model since 2017, calculating support based on both parents' net monthly incomes (after taxes). The guideline amount is the starting point, but courts may deviate based on special circumstances such as a child's extraordinary medical needs, travel costs for visitation, or significantly different financial situations from the guideline assumptions. Always confirm your specific calculation with a Illinois family law attorney.
Illinois uses both parents' gross monthly income as the starting point for child support calculations, combining them into a total family income figure. Courts may also impute income to a parent who is voluntarily underemployed or unemployed without good cause — meaning they may be held to what they could earn rather than what they actually earn.
No. In Illinois, shared custody reduces but does not eliminate child support in most cases. When both parents share custody equally, Illinois typically uses an offset method where each parent's guideline support is calculated and the higher earner pays the difference. The goal is to ensure the children maintain a similar standard of living in both households. If incomes are nearly equal, the resulting payment may be very small, but it rarely drops to zero unless incomes are identical.
In Illinois, child support generally continues until the child reaches the age of majority (typically age 18), graduates from high school, or is otherwise emancipated — whichever occurs later up to the state maximum. Courts may also continue support for adult disabled children who cannot support themselves. Support does not automatically end — the paying parent must file for termination when the child ages out or becomes emancipated.
Yes. Illinois child support can be modified when there is a substantial change in circumstances. Most states, including Illinois, require that the new calculated amount differ from the existing order by at least 15% — or that three years have passed since the order was entered, triggering an automatic review. Changes that typically qualify include significant income changes for either parent, a change in custody arrangement, a child's new medical needs, or loss of health insurance coverage. Modifications require filing a motion with the family court — the original order remains in effect until a new order is entered.