03/19/2026
How Child Support Is Calculated in Illinois?
Many parents assume child support is decided based on opinion or negotiation alone. In Illinois, however, child support is calculated using a structured legal model known as the Income Shares Model.
The goal of this model is simple: to estimate the amount parents would have spent on their child if they were living together and then divide that financial responsibility proportionally between both parents.
How the Calculation Generally Works
1. Combined Net Income
The court first determines each parent’s net income and combines both amounts.
2. Each Parent’s Percentage Share
Each parent’s financial responsibility is based on their percentage of the total combined income.
3. Basic Child Support Obligation
Illinois statutory guidelines provide tables that estimate the cost of raising a child at different income levels.
4. Parenting Time Adjustment
If both parents exercise significant parenting time (generally 146 overnights or more per year), the calculation may be adjusted to reflect shared parenting responsibilities.
5. Additional Expenses
Courts may also allocate:
Health insurance premiums
Childcare expenses
Extracurricular costs
Educational or medical expenses
While the formula provides guidance, every case involves unique financial and parenting circumstances.
Understanding how child support is calculated can help parents approach the process with clearer expectations and less uncertainty.
We welcome general questions or experiences related to child support matters—every family situation brings different considerations.
This post is for general informational purposes only and is not legal advice.