Illinois Child Support Calculator
Estimate child support payments using Illinois Income Shares guidelines
Illinois Calculator
Get accurate results
Updated for 2025 with real Illinois rates, brackets, and regulations
Illinois uses the Income Shares Model for calculating child support under 750 ILCS 5/505. The guidelines establish base percentages of combined net income: 20% for 1 child, 28% for 2 children, 32% for 3 children, 40% for 4 children, 45% for 5 children, and 50% for 6 or more children. Both parents' net incomes are combined, and each parent's share is proportional to their contribution to the total. The calculation adjusts for parenting time (overnights), health insurance premiums, childcare costs, and extraordinary expenses. Courts can deviate from guidelines with documented justification. Our calculator uses the official Illinois schedule to estimate your obligation.
Calculate Your IL Tax
Monthly Child Support
1,680$/mo
Annual Support
$20,160
IL Guideline %
28% (2 children)
Combined Income
$10,000/mo
Your Income Share
60.0%
Payer Overnights/Yr
73
Parenting Time Adj
None (< 146 nights)
Breakdown
Insight
IL child support for 2 children: $1,680/month using the IL Income Shares Model (effective since 2017). Illinois uses 28% of the COMBINED income of both parents, then apportions by each parent's income share. Your share: 60.0%. With 73 overnights/year, no parenting time adjustment applies. The threshold is 146+ overnights (40% of year). Healthcare, childcare, and extraordinary expenses are added to the base amount proportionally. Orders can be modified every 3 years or with a 20%+ income change. IL DCSS (Child Support Services) can assist with enforcement.
AI Explanation
What This Means
Based on default inputs, the Illinois Child Support Calculator shows a monthly child support of 1,680 $/mo. Key figures: Annual Support: $20,160, IL Guideline %: 28% (2 children), Combined Income: $10,000/mo, Your Income Share: 60.0%, Payer Overnights/Yr: 73, Parenting Time Adj: None (< 146 nights).
Key Insights
IL child support for 2 children: $1,680/month using the IL Income Shares Model (effective since 2017). Illinois uses 28% of the COMBINED income of both parents, then apportions by each parent's income share. Your share: 60.0%. With 73 overnights/year, no parenting time adjustment applies. The threshold is 146+ overnights (40% of year). Healthcare, childcare, and extraordinary expenses are added to the base amount proportionally. Orders can be modified every 3 years or with a 20%+ income change. IL DCSS (Child Support Services) can assist with enforcement.
What You Can Do
Enter your actual figures in the calculator above for a personalized breakdown. Consider consulting a tax professional for comprehensive planning, especially for complex situations involving multiple income sources or deductions.
Keep In Mind
This calculator provides estimates based on 2026 rates. Actual tax liability may vary based on credits, exemptions, and other factors not captured here. This is for educational purposes only and should not be considered tax advice.
How the Illinois Child Support Calculator Works
The Illinois Child Support Calculator uses 2026 tax rates, brackets, and deductions specific to Illinois to provide you with an accurate estimate of your tax obligations. Unlike generic federal-only calculators, this tool accounts for the unique tax structure that Illinois residents face.
Formula
Combined Net Income x Child Support Percentage (1 child: 20%, 2: 28%, 3: 32%, 4: 40%, 5: 45%, 6+: 50%) = Basic Support Obligation. Each parent's share = (Their Net Income / Combined Net Income) x Obligation. Adjustments for: parenting time, health insurance, childcare.Simply enter your financial details above, and the calculator instantly computes your results using the latest available data. All calculations happen directly in your browser — your personal information is never sent to any server or stored anywhere.
Why Use a Illinois-Specific Calculator?
State-Specific Rates
Uses real 2026 Illinois tax brackets, rates, and thresholds — not generic national averages that miss state-level nuances.
Local Programs & Exemptions
Factors in Illinois-specific programs, exemptions, and deductions that national calculators simply don't account for.
Instant & Private
All calculations run locally in your browser. No account required, no data stored, no waiting for results.
AI-Powered Explanations
Get a plain-English breakdown of your results with actionable insights you can actually use for financial planning.
What's Included
Official IL Guidelines
Uses the exact Illinois statutory percentages (750 ILCS 5/505): 20% for 1 child up to 50% for 6+ children.
Parenting Time Adjustment
See how your parenting time (overnights per year) affects the support amount — significant reductions at 146+ nights.
Add-On Expense Allocation
Factor in health insurance premiums, childcare costs, and extraordinary expenses split proportionally between parents.
Income Shares Breakdown
Understand how both parents' incomes determine each person's share of the total child support obligation.
Frequently Asked Questions
How is child support calculated in Illinois?
Illinois uses the Income Shares Model (750 ILCS 5/505). Both parents' net monthly incomes are combined. The guideline percentage is applied based on number of children: 1 child = 20%, 2 = 28%, 3 = 32%, 4 = 40%, 5 = 45%, 6+ = 50%. Each parent's share equals their percentage of combined income times the obligation. Adjustments are made for parenting time, health insurance, and childcare costs.
What counts as net income for Illinois child support?
Net income includes all income sources minus: federal and state taxes (4.95% IL flat tax), FICA/Social Security/Medicare, mandatory retirement contributions, union dues, health insurance premiums for the parent, and prior child support obligations. Income sources include: salary, wages, bonuses, commissions, self-employment income, disability benefits, unemployment, Social Security, rental income, and investment income.
How does parenting time affect Illinois child support?
Illinois provides a parenting time adjustment when the non-custodial parent has 146 or more overnights per year (40%+). At this threshold, a shared-care formula reduces the standard obligation to account for both parents' direct expenses during their parenting time. With 50/50 parenting time (182.5 nights each), support is reduced significantly but is rarely $0 unless incomes are equal.
Can Illinois child support be modified?
Yes. Either parent can petition for modification if there is a substantial change in circumstances: significant income change, job loss, change in parenting time, change in child's needs (medical, educational), or if the current order deviates by 20% or more from what the guidelines would produce. Either parent can request a review every 3 years. Modifications are not retroactive — the current order stays until the court changes it.
How long does child support last in Illinois?
Illinois child support continues until the child turns 18, or 19 if still attending high school. College support (Section 513) can be ordered for children attending college — Illinois is one of the few states that allows courts to order parents to contribute to college expenses. The court considers the financial resources of both parents, the child's academic performance, and the cost of the institution.
Important Information for Illinois Residents
Tax laws in Illinois can change annually. This calculator is updated regularly to reflect the latest 2026 rates and regulations, but you should always verify important financial decisions with a qualified Illinois tax professional or CPA.
This tool is designed for informational and educational purposes. While we strive for accuracy using official Illinois Department of Taxation data, the results should be used as estimates for planning purposes only. Your actual tax liability may differ based on credits, special circumstances, and legislative changes that occur after our last update.
For filing deadlines, payment schedules, and official forms, visit the Illinois Department of Taxation and Finance website. If you have complex tax situations involving multiple states, business income, or significant investment gains, professional guidance is recommended.
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