Illinois Child Support Calculator
2026Estimate child support payments in Illinois. Calculate expected IL child support obligations based on income, custody arrangement, and number of children using Illinois guidelines.
Written and reviewed by Konstantin Iakovlev · Methodology · Updated
Illinois statutory rates: Illinois uses an Income Shares schedule: combined net income runs through a state-published table to find the basic obligation. The calculator below uses generic Income Shares percentages and may not exactly match Illinois's schedule — use it for ballparking, then run the official Illinois guideline worksheet for any binding figure.
Total Annual Obligation
$37,600.00
Parent 1 Share
$27,072.00
Parent 2 Share
$12,032.00
Support Calculation
| Combined Gross Income | $100,000.00 |
| Base Obligation Rate (2 children) | 28% |
| Base Support Obligation | $28,000.00 |
| + Child Care Costs (annual) | $6,000.00 |
| + Health Insurance (annual) | $3,600.00 |
| Total Obligation | $37,600.00 |
Each Parent's Share
| Parent 1 Income Share | 60.0% |
| Parent 1 Annual Obligation | $27,072.00 |
| Parent 1 Monthly | $2,256.00 |
| Parent 2 Income Share | 40.0% |
| Parent 2 Annual Obligation | $12,032.00 |
| Parent 2 Monthly | $1,002.67 |
| Per Child (annual) | $18,800.00 |
Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.
How is child support calculated in Illinois?
Illinois applies the Income Shares model. Both parents' gross incomes are combined and run through a guideline schedule that yields a basic monthly obligation. Each parent's share of that obligation is prorated by their percentage of combined income.
The calculation typically adjusts for: (1) work-related childcare, (2) the child's portion of health-insurance premiums, (3) extraordinary medical expenses, and (4) parenting time when overnights cross a state-defined threshold (e.g., 20%–40% depending on jurisdiction). Pre-existing support orders for other children, alimony paid, and mandatory retirement contributions also reduce gross income before the formula applies.
Guideline figures are presumptive — judges may deviate upward or downward when applying them would be unjust given the child's needs, the parents' resources, or other relevant factors. Illinois courts retain final discretion. Always confirm the current guideline tables and worksheet with the Illinois child support agency or family court.
Illinois child support: model, official calculator, enforcement agency
- Guidelines model
- Income Shares
- Official calculator
- Illinois Child Support Estimator (HFS HFS-3115)
Illinois adopted Income Shares effective July 2017 (replacing the prior Percentage of Obligor model) under 750 ILCS 5/505. Both parents' net incomes combine, applied to a Schedule of Basic Child-Support Obligations adjusted for the number of children. Illinois HFS uses the State Disbursement Unit (SDU) in Wheaton; the Division of Child Support Services administers the state's 600,000+ cases. The 2017 reform also added a parenting-time credit for noncustodial parents with 146+ overnights.
Illinois Key Rates & Limits (2026)
| State Income Tax | 4.95% (flat) |
| State Sales Tax | 6.25% |
| Minimum Wage | $15/hr |
Illinois child support — frequently asked questions
How is child support calculated in Illinois in 2026?
Illinois adopted the Income Shares model effective July 2017 under 750 ILCS 5/505, replacing the prior Percentage of Obligor model. Both parents' net incomes are combined and applied to the HFS Schedule of Basic Child Support Obligations. The Estimator on the HFS website (Form HFS-3115) is the official calculator. Illinois HFS uses the State Disbursement Unit in Wheaton; the Division of Child Support Services administers more than 600,000 statewide cases.
Does Illinois give a parenting-time credit for shared custody?
Yes — under the 2017 reform, if the noncustodial parent has at least 146 overnights per year (40%), the calculation switches to the shared-parenting worksheet which proportionally reduces the obligation based on each parent's percentage of overnights. This is a higher threshold than many states, which means a parent with say 100 overnights gets no formal credit even though they incur substantial direct costs.
How long does child support last in Illinois?
Illinois child support generally ends when the child turns 18 or graduates from high school (whichever is later, but no later than age 19). However, under 750 ILCS 5/513, Illinois courts can order non-minor support for college and educational expenses through age 23 (or 25 with good cause) — including tuition, room and board, books, and medical insurance. Illinois is among the most generous states for post-majority educational support.