Illinois child support at a glance
- Guideline model: Income shares
- Income used: Net income: gross income minus a standardized or individualized tax amount (750 ILCS 5/505).
- Shared parenting time: If each parent has 146 or more overnights a year, the basic obligation is multiplied by 1.5 and split as a shared-care calculation (750 ILCS 5/505(a)(3.8)).
- When support ends: At 18; for a child still in high school, until graduation or age 19, whichever is earlier (750 ILCS 5/505).
Official calculator or worksheet: Illinois HFS child support estimator
This page explains the rules; it does not calculate an order. Health insurance, child care, other children and deviations change the result. Use the official tool and confirm with a family-law attorney licensed in Illinois.