Illinois Child Support Calculator — 2026 Estimate

Illinois uses the Percentage of Income to calculate child support. A fixed percentage of the non-custodial parent's income is applied based on the number of children. Use the calculator at childsupportestimate.com/illinois-child-support-calculator/ to enter your specific income and parenting time for an instant 2026 estimate.

Parenting time may or may not reduce child support in Illinois depending on specific circumstances — the base percentage does not automatically adjust.

Yes. Illinois child support orders can be modified when there is a substantial change in circumstances. Most states require a 10-15% change in the calculated guideline amount. Common grounds include income change, custody change, a new child, or a major change in the child's needs.

Illinois includes wages, salary, overtime, self-employment income, rental income, bonuses, commissions, investment income, and Social Security or disability benefits. Courts can impute income if a parent is voluntarily unemployed below their earning capacity.

Yes. In Illinois, health insurance premiums for the children and work-related childcare costs are added on top of the base child support obligation as add-ons, split proportionally between parents based on income.

File a motion to modify with the family court that issued the original order in Illinois. You must demonstrate a substantial change in circumstances. Use the modification calculator at childsupportestimate.com/modification-calculator to estimate whether your change meets the threshold before filing.

Not always — but if there is disagreement about income, parenting time, or add-ons in Illinois, or if you face modification, enforcement, or arrears, a family law attorney significantly improves your outcome. Most Illinois family law attorneys offer free initial consultations.