Illinois Child Support Guidelines
Illinois switched from a flat percentage model to the income shares model in 2017 under 750 ILCS 5/505. Both parents’ net incomes are combined and the statutory schedule determines the basic obligation. Each parent’s share is proportional to their income.
Illinois follows the Income Shares approach to calculating child support. The base percentages used in Illinois are approximately:
| Children | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
| Guideline % | 20% | 28% | 32% | 36% | 40% | 44% |
How Illinois Calculates Child Support
Under the Income Shares model, Illinois considers the combined gross income of both parents to determine the total child support obligation. The idea is that children should receive the same proportion of parental income they would have enjoyed if the parents lived together. Each parent's share is then calculated based on their percentage of the combined income.
In practice, the court looks up the combined parental income on a guidelines schedule to find the basic child support obligation. Each parent is then responsible for their proportional share. For example, if Parent A earns 60% of the combined income, they would be responsible for 60% of the obligation.
Key Factors in Illinois Child Support
Illinois courts consider several factors when determining child support obligations:
- Healthcare costs
- Childcare
- Education
- Extracurricular activities
- Number of children requiring support
- Each parent's gross income
- Parenting time / overnight schedule
Self-Support Reserve
Illinois protects a self-support reserve of $1,216/month to ensure the paying parent can meet their own basic needs. If the obligor's income falls below this threshold, the court may reduce or suspend the child support obligation.
Illinois Child Support Income Cap
Illinois applies an income cap of $360,000/year (approximately $30,000/month) for child support calculations. Income above this cap may be treated differently — courts have discretion to apply the standard guidelines percentage or deviate based on the children's needs and the family's standard of living.
If your combined household income exceeds $360,000, the court may consider additional factors such as the children's established lifestyle, educational needs, and extraordinary expenses.
Shared Custody in Illinois
Illinois's shared custody threshold is 28% of overnights (approximately 102 nights per year). When the noncustodial parent has the child for at least this many overnights, the standard child support calculation is adjusted downward to reflect the direct spending that occurs during parenting time.
The more overnights the noncustodial parent has beyond the 28% threshold, the greater the reduction in child support. In a true 50/50 custody arrangement, the higher-earning parent typically pays the difference between what each parent would owe based on their income share.
Illinois Child Support FAQ
How is child support calculated in Illinois?
Illinois uses the Income Shares model. Illinois switched from a flat percentage model to the income shares model in 2017 under 750 ILCS 5/505. Both parents’ net incomes are combined and the statutory schedule determines the basic obligation. Each parent’s share is proportional to their income. The guidelines were last updated in 2025.
What income is included in Illinois child support?
Illinois considers most forms of income including wages, salaries, bonuses, commissions, self-employment earnings, rental and investment income, pensions, Social Security benefits, disability payments, and unemployment compensation. Pre-existing child support orders, mandatory taxes, and certain mandatory retirement contributions may be deducted.
Can Illinois child support be modified?
Yes. Either parent can petition the court to modify child support when there has been a substantial change in circumstances. Common reasons include a significant increase or decrease in either parent's income (typically 15-25%), a change in the custody arrangement, a change in the child's medical or educational needs, or a change in childcare costs. The modification takes effect from the date the motion is filed, not retroactively.
How long does child support last in Illinois?
In most cases, Illinois child support obligations continue until the child turns 18. Support may be extended if the child is still attending high school (typically until age 19 or graduation, whichever comes first). If the child has a disability that prevents self-support, the obligation may continue indefinitely. Some states also allow support through college — check Illinois's specific statutes.
What if a parent doesn't pay child support in Illinois?
Illinois takes child support enforcement seriously. The state child support agency can pursue several remedies including automatic wage garnishment, interception of federal and state tax refunds, suspension of driver's and professional licenses, denial of passport applications, seizure of bank accounts, placement of liens on property, and contempt of court proceedings that can result in fines or incarceration. Unpaid child support also accrues interest in most cases.