Illinois Child Support Calculator

Estimate IL guideline child support under the income shares model (750 ILCS 5/505). Both parents' net incomes determine the basic obligation. Includes healthcare, childcare, extracurricular expenses, and shared parenting formula for 146+ overnights.

Updated April 2026 750 ILCS 5/505 (income shares, 2024 guideline) Private — runs in your browser

Obligor Monthly Gross Income

Non-custodial parent gross income

Obligee Monthly Gross Income

Custodial parent gross income

Number of Children

Illinois Child Support (Guideline)

$1,699/mo

Obligor Net$4,297/mo

Combined Net$6,936/mo

Basic Obligation$1,942/mo

Obligor Share62.0%

Illinois uses income shares based on combined net income (750 ILCS 5/505). Net income = gross minus standardized taxes.

Advanced Calculator

Net income shares visualization, shared parenting deviation analysis at multiple overnight schedules, and 10-year year-by-year projection with income growth.

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Illinois Inputs

Obligor Annual Gross Income

Obligee Annual Gross Income

Children

Healthcare Premium/mo

Work Childcare/mo

Illinois Child Support (Income Shares)

$1,637/mo

Obligor Net/mo$4,297

Combined Net$6,936/mo

Basic Obligation$1,942/mo

Obligor Share62.0%

Net Income Shares Split (IL uses net, not gross)

Basic Obligation (2 children): $1,942/mo

Obligor Support vs Obligee Gross Income

Higher obligee income → obligor pays less (IL income shares model)

Professional Simulator

Full income breakdown for both parents, all 750 ILCS 5/505 adjustments, parenting time financial impact, what-if income scenarios, and lifetime NPV projection.

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Obligor Income — Annual: $72,000

Wages / Salary

Self-Employment Net

Bonuses

Rental / Other Income

Obligee Income — Annual: $42,000

Wages / Salary

Other Income

Children & Adjustments

Children

Healthcare Premium/mo

Work Childcare/mo

Extracurricular/mo

Dental/Vision/mo

Illinois Professional Child Support Analysis

$1,730/mo

Net Income Calculation

Obligor gross: $6,000/mo

Obligor net: $4,297/mo

Obligee net: $2,639/mo

Combined net: $6,936/mo

Basic obligation: $1,942/mo

Obligor share: 62.0% = $1,203/mo

Adjustments (Obligor Share)

Healthcare: +$155/mo

Childcare: +$279/mo

Extracurricular: +$62/mo

Dental/Vision: +$31/mo

Total: $1,730/mo

% of Obligor Net40.3%

Annual Obligation$20,756/yr

How Illinois Child Support Works

Illinois uses the Income Shares Model under 750 ILCS 5/505, effective since July 2017. Both parents' net incomes are combined to determine a basic support obligation from the IL schedule, then each parent pays their proportionate share. The paying parent (obligor) remits their share directly; the receiving parent (obligee) fulfills their share through direct childcare.

Illinois Net Income Calculation

Illinois uses net income — not gross — as the starting point. Net income is gross income minus: federal and state income taxes (computed at single-filing rates), FICA (Social Security and Medicare), mandatory union dues, and health insurance premiums paid for the children. Illinois has a flat 4.95% individual income tax rate, which is factored into the standardized tax amounts.

Net Income = Gross Income − (Federal Tax + Illinois Tax 4.95% + FICA 7.65% + Union Dues + Health Insurance)
Combined Net = Obligor Net + Obligee Net
Basic Obligation = IL Schedule Lookup (Combined Net × Children Count)
Obligor's Share = Basic Obligation × (Obligor Net / Combined Net)

Shared Parenting (146+ overnights/yr):
Adjusted Support = Obligor Share × [1 − (Overnights/365 × 0.75)]

Total Support = Obligor's Basic Share + Healthcare Contribution + Childcare Contribution + Extracurricular

Example Calculation

Example: Two children, Chicago-area family

Obligor earns $6,000/month gross; obligee earns $3,500/month gross. Two children. Standard parenting schedule (73 overnights/year). Healthcare premium $250/mo, childcare $450/mo.

Obligor net income~$4,310/mo

Obligee net income~$2,580/mo

Combined net~$6,890/mo

Basic obligation (2 children)~$1,929/mo

Obligor share (62.6%)~$1,207/mo

Healthcare contribution+$157/mo

Childcare contribution+$282/mo

Total guideline support~$1,646/mo

Official Sources & Legal References

Frequently Asked Questions

Illinois 750 ILCS 5/505 defines gross income broadly: wages, salaries, commissions, bonuses, overtime, tips, self-employment income (gross receipts minus ordinary business expenses), rental income, investment income, Social Security benefits, disability payments, unemployment compensation, and pension/retirement income. Means-tested public assistance (SNAP, Medicaid) is excluded. Courts may impute income to voluntarily unemployed or underemployed parents.

Illinois applies the shared physical care formula when the non-custodial parent has 146 or more overnights per year (approximately 40% of overnights). At this threshold, the court uses a formula that accounts for the fact that both parents are bearing direct costs of caring for the children. Courts may further deviate based on the actual distribution of costs.

Healthcare insurance premiums for the children and work-related childcare costs (daycare, after-school care) are added to the basic support obligation, then divided proportionally by income share. Each parent pays their income-share percentage of these additional expenses. Extracurricular activity costs may also be divided by agreement or court order.

Illinois allows modification when there has been a substantial change in circumstances — generally a change of 20% or more in the support amount, a change in parenting time, a change in the child's needs, or a significant change in either parent's income. Illinois also allows review every three years without requiring proof of changed circumstances, as long as the review would result in a change of at least 20%.

In Illinois, when both maintenance (alimony) and child support are ordered, the child support calculation uses the obligor's net income after the maintenance payment is deducted. This means paying maintenance first effectively reduces the income base for child support. The combined guideline cap is 50% of net income for support obligations total. Courts also consider the children's standard of living.

When to Consult an Illinois Family Law Attorney

Illinois child support under 750 ILCS 5/505 uses net income shares — straightforward in theory, but complex in practice. Consult a licensed Illinois attorney if your case involves: self-employment income (gross receipts vs. expenses disputes), voluntary unemployment or imputed income, the shared parenting formula (146+ overnights), combined net income near schedule boundaries, or modification requests based on changed circumstances. The 20% change threshold for modification and the combined 50% net income cap create nuanced outcomes that require professional analysis.