Frequently Asked Questions
How is child support calculated in Illinois?
Illinois uses the income shares model under 750 ILCS 5/505. Both parents' net incomes are combined, a basic support obligation is determined from statutory guidelines, and each parent pays their proportionate share. The shared-physical-care formula applies when each parent has 146 or more overnights per year (at least 40% of the annual overnights).
What income counts for Illinois child support calculations?
Net income includes salary, wages, bonuses, commissions, self-employment income, rental income, and most other earnings. Courts can impute income if a parent is voluntarily unemployed or underemployed. Certain expenses like health insurance premiums and prior support obligations are deducted.
When can child support be modified in Illinois?
Under 750 ILCS 5/510, modification requires a substantial change in circumstances. Examples include 20%+ income change, job loss, disability, or significant changes in the child's needs. Support automatically continues until age 18 (or 19 if still in high school).
Written by Jonathan D. Steele
Chicago divorce attorney with cybersecurity certifications (Security+, ISC2 CC, Google Cybersecurity Professional Certificate). Illinois Super Lawyers Rising Star 2016-2025.
Request Conflict CheckGoing through a divorce? Get the checklist judges wish you had.
Download the free Illinois Divorce Preparation Checklist - the 30 things to do before your first court date. Plus weekly insights from a Chicago family law attorney.
For more insights, read our Divorce Decoded blog.