Child Support

Illinois uses an income shares model for child support. That means the calculation starts with both parents’ net incomes, not just one parent’s. Illinois moved to this model effective July 1, 2017.

In plain terms: the court estimates the total support amount that would typically be spent on the child(ren) if the parents were together, then assigns each parent a share based on income and parenting time. 

The Key Inputs Illinois Courts Use

Under Illinois’ child support statute (750 ILCS 5/505), the calculation typically depends on:

1) Each Parent’s Net Income

“Net income” is a legal calculation, not just what shows up on a paycheck. The definition and treatment of deductions are governed by statute. 

2) Number of Children

Support changes based on the number of children covered by the order. 

3) Parenting Time (Overnights)

Parenting time can change the guideline result. Illinois law includes a shared care adjustment when a parent has 146 or more overnights per year, using a multiplier built into the statute. 

4) Additional Child-Related Expenses

Depending on your facts, orders may address items like health insurance, uncovered medical expenses, childcare, and extracurricular costs (often handled in combination with the base support calculation). 

Use an Illinois Child Support Estimator (Helpful Starting Point)

If you want a quick estimate, Illinois HFS provides an official estimator/calculator to help parents approximate guideline support amounts based on the information entered.

Thinking Attorney tip: calculators are useful, but they don’t replace strategy, especially when income is irregular, self-employment is involved, or parenting time is disputed.

Establishing Child Support in Illinois

Child support can be set in:

• Divorce cases,
• Parentage cases (when parents were not married),
• Modifications of existing orders, and
• Cases involving enforcement when support hasn’t been paid.

Illinois courts generally follow the statutory framework in 750 ILCS 5/505 and require solid financial documentation to reach a guideline (or properly supported deviation) result. 

Can a Judge Deviate From the Guidelines?

Yes. The guidelines are the starting point, but courts can deviate when appropriate, so long as the result is supported by the statutory framework and the facts. This is where presentation matters: you need clean evidence and a clear explanation, not just frustration. 

Modifying Child Support in Illinois

Life changes, income changes, parenting time shifts, children’s needs evolve. Illinois allows modification of child support under 750 ILCS 5/510. 

Practical guidance: If you believe a modification is needed, timing matters. Support generally doesn’t change just because circumstances changed, you typically need to pursue the legal process to update the order. 

Enforcing Child Support Orders

If support isn’t being paid, enforcement tools may be available. Illinois law also states that a petition to modify or terminate support generally does not delay enforcement litigation on behalf of the obligee. 

Our role is to help you choose the most efficient enforcement path based on your goals (stability, compliance, and minimizing ongoing conflict).

Common Child Support Problems We Help Solve

Because “child support” is rarely just a number, we focus on the real-world issues that drive outcomes:

• Variable income (bonuses, commissions, seasonal work)
• Self-employment or business ownership (cash flow vs. taxable income)
• Underemployment claims and disputes about earning capacity
• Parenting time conflicts affecting the calculation (including shared care) 
• Unreimbursed medical / childcare cost disputes
• Enforcement when payments fall behind 

The Johnson Law Group North Star Approach

Child support outcomes improve when the work is organized, evidence-driven, and strategic.

We help you:

• Gather and present strong income documentation
• Build a guideline calculation that holds up
• Negotiate practical terms that reduce future conflict
• Pursue modification or enforcement with a clear plan under Illinois law 

Hablamos Español. Virtual options available.

FAQs: Illinois Child Support

How is child support calculated in Illinois?

Illinois uses an income shares model based on both parents’ net incomes, then allocates the obligation based on income percentages and parenting time.

What is the “146 overnights” rule I keep hearing about?

Illinois law provides a shared care adjustment when a parent has 146 or more overnights per year, applying a multiplier to the basic obligation and allocating it between parents based on income share. 

Can child support be changed after an order is entered?

Yes. Illinois allows modification under 750 ILCS 5/510, typically requiring a legally sufficient basis to modify and a proper court process. 

Is there an official Illinois child support calculator?

Yes, Illinois HFS provides a child support estimator and calculator tools to help generate an estimate using guideline concepts.