How Is Child Support Determined in Illinois?

The Short Answer

It depends on both parents’ financial information and the parenting arrangement. Illinois generally uses an income-shares guideline that estimates what the parents would spend on the child if they lived together and allocates support between them under the statutory framework.

Does Illinois Use Both Parents’ Incomes?

Generally, yes. The guidelines use the parents’ income information and convert income as required by the statute and current tables. The calculation can become more complicated when income fluctuates, a parent is self-employed, certain deductions apply, or income is disputed.

Does Parenting Time Affect Child Support?

It can. Illinois has separate rules for certain shared-care arrangements, and parenting time may affect the guideline calculation. The statutory thresholds and formulas are technical and can change, so a current worksheet or calculation should be used for an actual case.

What Other Child-Related Expenses Can Matter?

Depending on the case, health insurance, uninsured medical expenses, child care, school expenses, extracurricular activities and other child-related costs may be allocated in addition to the basic support obligation.

Can the Court Order a Different Amount Than the Guideline?

Sometimes. Illinois law allows deviations from the guideline amount when the statutory requirements are met. The court generally considers the child’s needs, the parents’ financial circumstances and other factors identified by law.

Can Child Support Change Later?

Possibly. A support order may be modified when the legal requirements for modification are satisfied. Changes in income, parenting arrangements, child-related expenses or other circumstances may be relevant, but a change in circumstances does not automatically change an existing order.

Bottom Line

Illinois child support is not based on one fixed percentage of one parent’s paycheck. The calculation can depend on both parents’ income, parenting time, child-related expenses and current guideline tables. A family-law attorney can review the actual financial information and existing court orders before advising on a specific amount.