Calculate Child Support
Before taxes. Include wages, self-employment, bonuses.
Illinois uses the Income Shares — both incomes required.
0 = no custody · 91 = 25% · 182 = 50/50 · 365 = full custody
$0
estimated monthly support payment
⚠️ Estimate only. Actual court-ordered amounts may vary. Verify with a licensed Illinois family law attorney.
ℹ️ Illinois uses the Income Shares — Illinois uses Income Shares. Support may extend to age 19 if in high school.
How Child Support Works in Illinois
Illinois uses the Income Shares to determine child support obligations.
The Income Shares model combines both parents' incomes, finds the basic support obligation from a state schedule, then divides it proportionally. More parenting time (overnights) reduces the non-custodial parent's payment through a parenting time credit.
How Illinois Compares to Other States
See how Illinois's child support rules compare to other states.
| State | Formula | Support Ends | Arrears Rate | Mod. Threshold |
|---|---|---|---|---|
| ★ Illinois (you) | Income Shares | 18 | 9% | 20% |
| Delaware | Melson Formula | 18 | 5% | 10% |
| Idaho | Percentage of Income | 18 | 5% | 15% |
| Michigan | Income Shares | 18 | 5% | 10% |
| Ohio | Income Shares | 18 | 5% | 10% |
| Alaska | Percentage of Income | 18 | 6% | 15% |
| Florida | Income Shares | 18 | 6% | 15% |
| Louisiana | Income Shares | 18 | 6% | 25% |
| New Hampshire | Income Shares | 18 | 6% | 15% |
Showing 8 comparison states. View all 50 states →
Frequently Asked Questions
How is child support calculated in Illinois?
Illinois uses the Income Shares model. Illinois uses Income Shares. Support may extend to age 19 if in high school.
When does child support end in Illinois?
Child support generally ends when the child turns 18 in Illinois.
Can I modify child support in Illinois?
Yes. Illinois requires a 20% or greater change in income to qualify. Use our modification checker →
Does 50/50 custody eliminate child support in Illinois?
Not automatically. The higher-earning parent typically still pays support with 50/50 custody. See our 50/50 guide →
What income is used for child support in Illinois?
Income includes wages, self-employment, bonuses, rental income, unemployment benefits, disability payments, and Social Security. Courts may impute income if a parent is voluntarily underemployed.