Illinois Child Support Calculator & Guide (2025)
Overview of Illinois Child Support
Illinois calculates child support using the Income Shares Model as defined in 750 ILCS 5/505. This model estimates the amount parents would spend on their children if the household were intact, then divides that obligation proportionally based on each parent's share of combined net income.
Illinois adopted the Income Shares Model on July 1, 2017, replacing the prior percentage-of-income system. The Illinois Child Support Guidelines use a table that lists basic child support obligations based on combined net income and the number of children.
How Child Support Is Calculated in Illinois
The calculation follows these steps:
- Determine gross income for both parents (salary, wages, bonuses, commissions, self-employment, disability, Social Security, unemployment, pensions, rental income)
- Calculate net income by subtracting allowable deductions (federal and state taxes, Social Security, Medicare, health insurance premiums, mandatory retirement contributions, union dues, prior support obligations)
- Combine net incomes to get total household income
- Find the base obligation from the Illinois Child Support Guidelines table based on combined income and number of children
- Add extra expenses — healthcare costs, childcare, and extraordinary medical expenses
- Allocate proportionally — each parent's share is based on their percentage of combined income
- Adjust for shared care if applicable (each parent has 146+ overnights per year)
Example Calculation
| Factor | Parent A | Parent B |
|---|---|---|
| Monthly Net Income | $5,000 | $3,000 |
| Combined Income | $8,000 | |
| Base Obligation (2 children) | ~$2,240 | |
| Income Share | 62.5% | 37.5% |
| Each Parent's Share | $1,400 | $840 |
| Parent A pays Parent B | ~$1,400/month | |
Key Factors in Illinois Calculations
Income Definition
Illinois considers all sources of income including employment income, self-employment income, disability benefits, Social Security benefits, unemployment compensation, pension and retirement income, rental income, and recurring gifts. The court may also impute income to a parent who is voluntarily unemployed or underemployed.
Shared Care Adjustments
When both parents have significant parenting time (each having at least 146 overnights per year), Illinois applies a shared care adjustment. This reduces the support obligation to account for the fact that both parents are directly providing for the children during their parenting time.
Health Insurance and Childcare
Health insurance premiums for the child and work-related childcare costs are added to the base obligation and shared proportionally between parents based on their income shares.
College Expenses
Under 750 ILCS 5/513, Illinois courts can order contributions to post-high school educational expenses including college tuition, housing, books, and medical expenses. This can extend support until the child turns 23, which is unique compared to many other states.
Minimum and Maximum Amounts
Illinois does not have a fixed statutory minimum or maximum child support amount. The guidelines are considered a rebuttable presumption. The court may deviate from the guideline amount if it finds that the guidelines would be inappropriate or unjust, provided written findings are made explaining the deviation.
For low-income parents, Illinois has a self-support reserve that ensures the paying parent retains enough income to meet their own basic needs.
Modification and Enforcement
Modification
Either parent can file a petition for modification with the circuit court. A substantial change in circumstances must be demonstrated, such as:
- Significant increase or decrease in either parent's income
- Change in custody or parenting time arrangement
- Change in the child's needs or medical condition
- Emancipation of a child
Modifications can be retroactive to the date the petition was filed.
Enforcement
The Illinois Department of Healthcare and Family Services enforces child support through:
- Income withholding orders
- Tax refund interception (state and federal)
- Driver's license suspension
- Professional license suspension
- Credit bureau reporting
- Passport denial for arrears exceeding $2,500
- Property liens
- Contempt of court proceedings
Get your Illinois child support estimate now: Use our free calculator to see what you might owe or receive under Illinois guidelines.
Frequently Asked Questions
How is child support calculated in Illinois?
When did Illinois switch to the Income Shares Model?
Does shared parenting affect child support in Illinois?
Can college expenses be included in Illinois child support?
What income is counted for Illinois child support?
How do I modify child support in Illinois?
Who enforces child support in Illinois?
Legal Disclaimer
This article is for informational purposes only and does not constitute legal advice. Child support laws vary by state and are subject to change. For advice specific to your situation, please consult a qualified family law attorney in your jurisdiction.