Illinois Child Support Calculator
Enter both parents' incomes, number of children, and parenting time to estimate the Illinois monthly child support obligation under the Income Shares model. Consult a family law attorney for a binding order.
- N/A
- 1-child base rate
- N/A
- base-rate rank
- No cap
- income ceiling
- 57.6%
- collection rate
The verdict
Illinois posts a collection rate near the national average.
According to PlainChildSupport's state guideline dataset.
- 57.6%
- collection rate
- 60.6%
- national average
How Illinois Calculates Child Support, and Why the Formula Matters
Illinois determines child support obligations using the Income Shares model, one of three approaches used across the United States.
How the three national child-support formula models differ
The Income Shares model (used by 41 states) combines both parents' incomes to estimate what the family would have spent on the children if intact, then divides that obligation in proportion to each parent's share of the combined income. The Percentage of Income model (used in states like Alaska, Mississippi, Nevada, North Dakota, Texas, and Wisconsin) takes a fixed percentage of the non-custodial parent's income based on the number of children. The Melson Formula, adopted in Delaware, Hawaii, and Montana, layers a self-support reserve on top of the Income Shares approach so neither parent's basic needs are consumed before the child's obligation is met.
This calculator applies the Illinois-specific statutory tables and adjustments: parenting-time credit adjusts the obligation when the non-custodial parent has substantial overnight visitation, and healthcare insurance and work-related childcare are typically added and split proportionally. The result is an estimate of presumptive support, state courts can and do deviate upward or downward based on factors like high income, extraordinary medical expenses, or the non-custodial parent's other dependents. For a binding order, the official Illinois worksheet must be filed with the court. Pair this calculator with the per-state guideline page for current multipliers, deviation factors, and review/modification thresholds.
Source: Illinois Child Support Guidelines · Methodology: statutory tables and adjustments as published · Estimate only, a court order requires the official worksheet.
Interactive Calculator for Illinois
Illinois uses the Income Shares to calculate child support. Both parents' combined income and each parent's share of it are used to look up the obligation on the state's published child support schedule.
Our Illinois interactive calculator is in development. Phase 1 covers the 10 largest states.
Use Official Illinois CalculatorIllinois Guideline Summary
Not published
1 Child
Not published
2 Children
Not published
3 Children
None
Income Cap
Other State Calculators
Read our methodology - how this data is sourced, computed, and verified.
All federal data sources used on this page
- HHS Office of Child Support Enforcement (OCSE) - federal child-support enforcement data. acf.hhs.gov/css
- HHS OCSE Annual Reports to Congress - state child-support program data. acf.hhs.gov/css/annual-reports
- U.S. Census Bureau Current Population Survey, Child Support Supplement - custodial-parent demographics + support amounts. census.gov/topics/families/child-support
- State Child Support Guidelines - state-specific formulas (income shares, percentage of income). acf.hhs.gov/css/state-guidelines
- IRS Treasury Offset Program - federal tax-refund intercept for past-due support. irs.gov/individuals/refund-offsets
- HHS Administration for Children and Families (ACF) - family policy and demographic context. acf.hhs.gov
Related
Source: U.S. Office of Child Support Services (OCSS) - HHS Child support enforcement caseload and collections · 2025
Every figure on PlainChildSupport is rendered directly from official state guidelines and federal enforcement data, no number is typed in by an editor. This page draws directly on official state guidelines and federal enforcement data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.