How Illinois Child Support Is Calculated
Illinois child support follows the Income Shares Model, which calculates support based on what both parents would have spent on their children if they were living together. The Illinois Department of Healthcare and Family Services publishes official support schedules that courts use to determine guideline obligations.
Key Factors in Illinois Child Support Calculations
Both Parents' Incomes
Illinois considers the gross income of both parents from all sources. This includes wages, salaries, self-employment income, commissions, bonuses, rental income, investment income, unemployment benefits, workers' compensation, Social Security benefits, pensions, and most other income sources. The court may impute income to a parent who is voluntarily unemployed or underemployed.
Number of Children
The basic obligation increases with each additional child, but the per-child cost decreases slightly due to economies of scale. Illinois guidelines provide specific obligation amounts based on combined income and family size. Support for 3 children is not simply 1.5× the support for 2 children.
Parenting Time (Overnights)
Parenting time significantly impacts the final support amount. When a parent has substantial parenting time (typically 146+ overnights per year, or about 40%), they incur direct costs for the child during that time. Illinois courts may apply a formula-based adjustment that reduces the basic obligation proportionally.
Additional Expenses (Add-Ons)
| Expense Type | How It's Handled |
|---|---|
| Health Insurance | Cost of covering the child is added to basic obligation, shared proportionally |
| Uninsured Medical Expenses | First $250 per child per year is paid by the custodial parent; excess shared proportionally |
| Childcare | Work-related or education-related childcare costs shared proportionally |
| Extracurricular Activities | Court may order proportional sharing of reasonable extracurricular expenses |
Income Cap and Deviations
Illinois guidelines apply to combined parental income up to $30,000 per month. For income above this cap, the court has discretion to order additional support based on the child's needs and the parents' standard of living. Courts can also deviate from guidelines for special circumstances including: extraordinary medical needs, special needs children, high conflict custody situations, and agreements between parents.
How Child Support Is Paid
Illinois generally requires child support to be paid through the State Disbursement Unit (SDU), which maintains payment records and can enforce collection through wage withholding, tax refund interception, and other mechanisms. Most support orders include automatic wage withholding unless both parents agree otherwise and the court approves.
Modification of Child Support Orders
- Every 3 years: Either parent can request review without proving changed circumstances
- Substantial change: Support can be modified anytime if there is a substantial change in circumstances (e.g., job loss, income increase ≥ 20%, change in parenting time)
- Child reaching majority: Support typically continues until age 18 (or 19 if still in high school)
- Emancipation: Support for a child ends upon marriage, military service, or full-time employment of the child
Important Disclaimer
This calculator provides an educational estimate based on Illinois child support guidelines. Actual support amounts may differ based on specific court findings, deviations, and judicial discretion. This tool is not a substitute for legal advice. Consult a licensed Illinois family law attorney for your specific situation.
Sources and References
- Illinois Department of Healthcare and Family Services — Child Support Services
- 750 ILCS 5/505 — Illinois Marriage and Dissolution of Marriage Act
- Illinois Child Support Guidelines — Income Shares Schedule
- Illinois State Disbursement Unit (SDU)