How Child Support is Calculated in Illinois
Illinois switched to an Income Shares model in 2017. The Illinois Department of Healthcare and Family Services publishes a Basic Support Obligation table, and each parent contributes a share proportional to their net income. Adjustments apply when each parent has 146+ overnights per year (shared physical care).
Estimated Monthly Child Support in Illinois
Below are sample calculations using our Illinois formula. These figures assume the higher-earning parent pays support and exclude childcare or insurance add-ons.
| Your Income | Other Parent | 1 Child | 2 Children | 3 Children |
|---|---|---|---|---|
| $3,000/mo | $3,000/mo | ~$720 | ~$1,260 | ~$1,692 |
| $4,000/mo | $2,500/mo | ~$880 | ~$1,540 | ~$2,068 |
| $6,000/mo | $3,000/mo | ~$1,200 | ~$2,100 | ~$2,820 |
What Can Increase or Decrease Payments in Illinois?
- Each parent's gross monthly income from all sources
- The number of children covered by the order
- Health insurance premiums paid for the children
- Work-related childcare and daycare expenses
- How much overnight parenting time each parent has
- Any extraordinary medical, educational, or special-needs costs
How to File for Child Support in Illinois
- Open a case with Illinois's Department of Child Support Services (or the equivalent state agency).
- Provide proof of both parents' income — pay stubs, tax returns, or a financial affidavit.
- Submit a parenting plan or custody order showing each parent's overnight time.
- Attend a hearing or administrative review where a judge or referee finalizes the order.
Frequently Asked Questions — Illinois Child Support
What is the Illinois shared parenting threshold?
When each parent has at least 146 overnights (40%) per year, Illinois uses a shared physical care formula that multiplies the basic obligation by 1.5.
Are bonuses included in Illinois income?
Yes. Illinois defines income broadly — wages, bonuses, commissions, business income, and most government benefits all count.
Can Illinois deviate from the guideline?
Courts may deviate when the guideline result would be inappropriate or unjust, with written findings explaining the deviation.
When does Illinois child support end?
Generally when the child turns 18 or graduates high school (up to age 19), with extensions possible for disabled children or college expenses by court order.