Does 50/50 custody mean no child support in Illinois?

No. Even with equal parenting time, the higher-earning parent typically pays some support to equalize resources in both homes. Illinois uses a shared parenting formula when each parent has 146+ overnights (40%), which reduces but rarely eliminates the obligation entirely.

What income counts for child support in Illinois?

Illinois counts all income sources: wages, salary, bonuses, commissions, self-employment income, investment returns, rental income, Social Security, pensions, and more. Courts can also impute income if a parent is voluntarily unemployed or underemployed.

How long does child support last in Illinois?

Child support typically ends when the child turns 18, or 19 if still in high school. Support can extend for college expenses (non-minor support) and indefinitely for disabled adult children. Courts can also order contribution to college costs under Section 513.

Can child support be modified in Illinois?

Yes, child support can be modified when there's a substantial change in circumstances—typically a 20% change in either parent's income, or significant changes in parenting time or the child's needs. Either parent can file a motion to modify.

What is the maximum child support in Illinois?

The Illinois guidelines apply to combined net incomes up to $30,000/month ($360,000/year). Above that threshold, courts have discretion to set support based on the child's needs and family's standard of living. There's no fixed maximum percentage.

Illinois Child Support

Q: How is child support calculated in Illinois?

Illinois uses the Income Shares Model under 750 ILCS 5/505. Both parents' net incomes are combined to determine a basic support obligation based on the number of children. Each parent pays their proportionate share. The non-custodial parent typically pays their share to the custodial parent.

How support is calculated, when it can be modified, and what to do if your ex won't pay. Everything you need to know in one place.

Quick Answer: Illinois uses the "Income Shares Model." Both parents' incomes are combined, a basic obligation is calculated, and each parent pays their proportionate share. The non-custodial parent pays their share to the custodial parent.

How Child Support is Calculated in Illinois

Under 750 ILCS 5/505, Illinois calculates child support using a four-step process:

Step 1

Calculate Net Income

Convert gross income to "standardized net income" using statutory deductions for taxes and certain expenses.

Step 2

Combine Incomes

Add both parents' net incomes together to get the combined net income.

Step 3

Find Basic Obligation

Use the Illinois schedule to find the basic support obligation based on combined income and number of children.

Step 4

Divide Proportionally

Each parent pays their percentage share. Non-custodial parent pays their share to custodial parent.

Example Calculation

Scenario: 2 children, Mom earns $80,000/year, Dad earns $120,000/year

Mom's Net Income	$4,800/month
Dad's Net Income	$7,200/month
Combined Net Income	$12,000/month
Basic Obligation (2 kids)	$2,289/month
Mom's Share (40%)	$916/month
Dad's Share (60%)	$1,373/month

If Mom has primary custody, Dad pays his $1,373 share to Mom. Mom's share is assumed spent directly on the children.

Shared Parenting: The 146-Night Rule

When each parent has the children at least 146 overnights per year (40%), Illinois uses a different formula that accounts for the time split:

Shared Parenting Formula: The basic obligation is multiplied by 1.5, then each parent's share is adjusted based on their percentage of overnights. The result typically means the higher earner still pays, but less than under standard guidelines.

Does 50/50 = No Child Support?

Almost never. Even with perfectly equal time, income disparity creates an obligation. The purpose is to ensure the child has similar resources in both homes.

50/50 Example: Same incomes as above, but equal parenting time

Dad's Adjusted Obligation

~$685/month

Dad still pays, but about half of what he'd pay under standard guidelines. The formula ensures Mom's household has comparable resources.

Warning: Courts are suspicious when a parent suddenly demands more parenting time right before support calculations. Your motivation matters. Fight for time because you want to parent, not to reduce support.

What Counts as "Income"?

Illinois defines income broadly under 750 ILCS 5/505(a)(3). Almost everything counts:

Included as Income

• Wages, salary, tips
• Bonuses and commissions
• Self-employment income
• Investment income & dividends
• Rental income
• Social Security benefits
• Pensions and retirement
• Unemployment benefits
• Workers' comp
• Trust distributions

NOT Included

• Child support received for other children
• Public assistance (TANF, SNAP)
• Foster care payments
• SSI (Supplemental Security Income)

Imputed Income

If a parent is voluntarily unemployed or underemployed, courts can impute income—calculate support based on what they could earn rather than what they actually earn.

Common Imputation Scenarios: Quitting a job before divorce, taking a lower-paying position, refusing to seek employment, hiding income in a cash business, or having a new spouse support them.

Modifying Child Support

Child support is never truly "final." Either parent can request modification when circumstances substantially change:

Automatic Review Triggers

• 20% income change in either parent's income
• Healthcare cost changes exceeding $50/month
• Parenting time changes crossing the 146-night threshold
• Child's needs change (special education, medical conditions)

How to Modify

1. File a Petition to Modify with the court that entered the original order
2. Document the substantial change (pay stubs, tax returns, medical records)
3. Attend hearing and present evidence
4. Court enters new order—modifications are not retroactive

Critical: Modifications are NOT retroactive. Even if you lose your job, you owe the original amount until the court enters a new order. File immediately when circumstances change.

Child Support Duration

Situation	Support Ends
Standard termination	Age 18 (or 19 if still in high school)
Child marries	Upon marriage
Child joins military	Upon enlistment
Emancipation	Upon court order
Disabled adult child	May continue indefinitely
College expenses (Section 513)	Court may order contribution

College Costs: Illinois is one of few states that can order divorced parents to contribute to college expenses under Section 513. This is separate from child support and considers the child's academic ability, financial resources of both parents, and the standard of living the child would have enjoyed.

Enforcement: When Your Ex Won't Pay

Illinois has powerful enforcement tools when a parent fails to pay court-ordered support:

Income Withholding

Automatic deduction from paycheck through employer. Now standard in all cases.

License Suspension

Driver's license, professional licenses, hunting/fishing licenses can be suspended.

Tax Refund Intercept

State and federal tax refunds can be seized for past-due support.

Contempt of Court

Willful non-payment can result in fines and even jail time.

Credit Reporting

Arrears over $1,000 are reported to credit bureaus.

Passport Denial

Arrears over $2,500 can prevent passport issuance or renewal.

Important: You cannot withhold parenting time because your ex isn't paying support. Support and parenting time are legally separate issues. Denying visitation can hurt your custody case.

Frequently Asked Questions

How is child support calculated in Illinois? +

Illinois uses the Income Shares Model. Both parents' net incomes are combined, a basic obligation is determined from state guidelines based on number of children, and each parent pays their proportionate share. The non-custodial parent pays their share to the custodial parent.

Does 50/50 custody mean no child support? +

No. Even with equal parenting time, the higher-earning parent typically pays some support. The shared parenting formula (for 146+ overnights each) reduces the obligation but rarely eliminates it. The goal is ensuring similar resources in both homes.

What income counts for child support? +

Almost all income counts: wages, bonuses, commissions, self-employment, investments, rental income, retirement, Social Security, unemployment, and more. Courts can also impute income if a parent is voluntarily underemployed.

Can child support be modified? +

Yes, when there's a substantial change in circumstances—typically a 20% change in income, significant parenting time changes, or changes in the child's needs. File a petition immediately when circumstances change; modifications aren't retroactive.

How long does child support last? +

Support typically ends at 18 (or 19 if still in high school). It can extend for college expenses under Section 513, and may continue indefinitely for disabled adult children. Support ends earlier if the child marries, joins the military, or is emancipated.

What if my ex won't pay child support? +

Illinois has strong enforcement tools: income withholding, license suspension, tax refund intercept, credit reporting, passport denial, and contempt of court. Do NOT withhold parenting time—that's a separate legal issue and can hurt your case.

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This article is for informational purposes only and does not constitute legal advice. No attorney-client relationship is created by reading this content.