Illinois Child Support Laws: Guidelines and Calculations

Overview of Illinois Child Support Guidelines

Illinois uses the Income Shares Model for calculating child support obligations. The state adopted this model on July 1, 2017, replacing the older "Percentage of Non-Custodial Parent Income" method. Under the Income Shares Model, child support reflects the combined financial resources of both parents, ensuring children receive the same proportion of parental income they would have received if the family remained intact.

The Illinois Department of Healthcare and Family Services (HFS) establishes and maintains the child support guidelines. These guidelines include worksheets, income conversion tables, and obligation schedules that courts and parents use to determine support amounts. A federally mandated quadrennial review process ensures the calculations stay fair and reflect current economic conditions. The most recent comprehensive review was completed in 2022, and the next quadrennial review is scheduled for completion in 2026.

How Child Support Is Calculated in Illinois

Under 750 ILCS 5/505, Illinois courts follow a specific process to calculate child support:

1. Determine each parent's monthly net income by subtracting allowable deductions from gross income.
2. Combine both parents' monthly net incomes to find the total combined net income.
3. Look up the basic child support obligation using the Schedule of Basic Child Support Obligations based on combined income and number of children.
4. Calculate each parent's percentage share of the combined income.
5. Apply each parent's percentage to the basic support obligation to determine their individual share.

The parent who does not have primary physical custody typically pays their share to the custodial parent. To estimate a support amount for your situation, HFS provides an official Illinois Child Support Estimator.

Example Calculation

If Parent A earns $4,000 per month in net income and Parent B earns $2,000 per month:

Factor	Amount
Parent A net income	$4,000/month
Parent B net income	$2,000/month
Combined net income	$6,000/month
Parent A's share	67% ($4,000 / $6,000)
Parent B's share	33% ($2,000 / $6,000)

The Schedule of Basic Support Obligations provides the total support amount for two parents with $6,000 combined income based on the number of children. Each parent's share is then calculated using their percentage of the combined income.

Shared Parenting Adjustment

When each parent exercises 146 or more overnights per year with the child, a shared parenting formula applies. Under this adjustment, the basic child support obligation is multiplied by 1.5. Each parent's portion is then calculated based on their share of combined income and the percentage of time the child spends with the other parent. The two amounts are offset, and the parent who owes more pays the difference.

Accurate records of actual overnight parenting time are critical. Illinois law directs courts to consider actual parenting time, not just the schedule written in the parenting plan, when determining whether the shared formula applies.

What Counts as Income in Illinois

Illinois calculates child support based on "net income," which is gross income minus specific deductions.

Gross Income Includes

• Salaries, wages, tips, and commissions
• Bonuses and overtime pay
• Self-employment income
• Interest and dividend income
• Rental income
• Pension and retirement benefits
• Social Security benefits
• Unemployment and workers' compensation benefits
• Disability benefits
• Spousal maintenance (alimony) received

Sources Excluded from Gross Income

• Public assistance benefits (TANF, SNAP, and similar programs)
• Income and benefits received for other children in the household
• Child support received for children from another relationship

Allowable Deductions

The following deductions are subtracted from gross income to arrive at net income:

• Federal and state income taxes (based on proper withholding rates)
• FICA contributions (Social Security and Medicare taxes)
• Mandatory retirement contributions
• Union dues
• Health insurance premiums for the parent only
• Prior child support obligations ordered by a court
• Spousal maintenance paid under a court order

Imputed Income for Unemployed or Underemployed Parents

If a parent is voluntarily unemployed or underemployed, the court may impute income based on that parent's earning capacity. Courts consider work history, education, professional qualifications, job opportunities in the area, and prevailing earnings levels in the community.

Effective January 1, 2025, amendments to 750 ILCS 5/505 strengthened the imputed income provisions. Courts can now assign an income figure to a parent who chooses not to work or works below their earning capacity, closing loopholes that previously allowed some parents to reduce their obligations by voluntarily reducing their income.

Recent Changes to Illinois Child Support Laws

Illinois has made several important updates to child support guidelines in recent years.

2025 Updates

Both the Gross to Net Income Conversion Table and the Income Shares Schedule of Basic Child Support Obligations were revised with new amounts effective March 5, 2025. Since 2024, Illinois updates both tables annually, whereas previously only the Gross to Net table received yearly updates.

The income imputation amendments that took effect January 1, 2025, give courts stronger tools to address parents who voluntarily reduce their income to lower support obligations.

2024 Changes

Illinois eliminated the automatic 9% annual interest rate on child support arrears. Interest on past-due support now requires a specific court order, allowing custodial parents to decide whether to seek interest on overdue payments. This change removes a punitive element and makes it easier for parents who owe back support to catch up on payments.

The state also introduced the "Families First" policy, which guarantees that custodial parents departing from welfare receive all child support arrearages collected while they were receiving public assistance.

2026 Quadrennial Review

The next comprehensive quadrennial review of the Illinois child support guidelines is scheduled for completion in 2026. This review will evaluate whether the current schedules and calculation methods remain appropriate for Illinois families and may result in updated obligation amounts.

How to Modify Child Support in Illinois

Under 750 ILCS 5/510, Illinois allows modification of child support orders through two main paths.

Path 1: Substantial Change in Circumstances

A parent can petition for modification by demonstrating a substantial change in circumstances since the order was entered. Examples include:

• Involuntary job loss or significant income reduction
• A substantial increase in either parent's income
• Disability or serious illness
• Changes in the child's needs (medical expenses, educational needs)
• Incarceration of the paying parent

Path 2: Guideline Deviation

Modification is available without proving a substantial change if there is an inconsistency of at least 20% (but no less than $10 per month) between the current order and the amount that would result from applying the current guidelines.

Types of Modification Processes

• Judicial orders are modified through the court system by filing a petition.
• Administrative orders are modified through Health Care and Family Services.
• DCSS Health Care Modifications can be requested by calling 1-800-447-4278.

Important Rules for Modifications

The court will not grant a modification retroactive to before the date the other parent received notice of the petition. Any support owed before the filing date remains owed at the original amount.

A court may deny a modification request if it finds the petitioning parent is voluntarily unemployed or underemployed to reduce their support obligation.

Enforcement of Child Support Orders

Illinois takes enforcement of child support orders seriously. Parents can apply for enforcement services or check amounts owed through the Division of Child Support Services.

Administrative and Civil Enforcement Methods

Method	Description
Income withholding	Automatic payroll deductions from the paying parent's employer
Bank account garnishment	Seizure of funds from bank accounts
License suspension	Suspension of driver's, professional, and recreational licenses
Property liens	Liens against real estate and personal property
Tax refund intercept	Interception of state and federal tax refunds
Passport denial	Denial or revocation of passport if arrears exceed $2,500
Credit bureau reporting	Reporting delinquent support to credit agencies

Criminal Penalties Under the Non-Support Punishment Act

Under the Non-Support Punishment Act (750 ILCS 16), failure to pay child support can result in criminal prosecution:

Violation	Classification	Potential Penalty
Arrearage over $5,000	Class A misdemeanor	Up to 1 year in jail
Leaving the state to evade support	Class 4 felony	1 to 3 years in prison
Arrearage over $20,000 or failure to pay for 1+ year	Class 4 felony	1 to 3 years in prison

Delinquent Parents Program

Under the Illinois Public Aid Code, 305 ILCS 5/12-12.1, when back support exceeds $5,000, the state can publicly list delinquent parents on a "most wanted child support offenders" list.

Debt Forgiveness Program

Illinois offers a debt forgiveness program that can permanently remove past-due payments owed to the state. Parents may qualify if they experienced disability, incarceration, or involuntary job loss. Contact the Division of Child Support Services at 1-800-447-4278 for eligibility information.

When Child Support Ends in Illinois

Child support in Illinois normally terminates when the child reaches age 18. However, several circumstances can extend or shorten that timeline.

Support Continues Beyond 18 When

• The child is still in high school. Support continues until the child graduates or turns 19, whichever comes first.
• The child has a disability. If a child has special needs that prevent self-sufficiency, support may continue indefinitely.
• Parents agree to extended support. Written agreements can extend support beyond age 18 for specific purposes.

College and Educational Expenses Under 750 ILCS 5/513

Illinois is one of the few states that allows courts to order parents to contribute to college and post-secondary educational expenses. Under 750 ILCS 5/513, either parent can petition for contribution to educational costs including:

• Tuition and fees
• Room and board
• Books and supplies
• Medical insurance and dental expenses
• Transportation costs
• Application and registration fees

The maximum contribution is capped at the cost of attending the University of Illinois at Urbana-Champaign (tuition, fees, and standard double-occupancy room and board). The child must maintain at least a C average. Payments end no later than the child's 23rd birthday, or age 25 if a court finds good cause for the delay (such as military service or illness).

Courts consider both parents' financial resources, the standard of living the family would have enjoyed, the child's own financial resources, and the child's academic performance when ordering educational contributions.

Support May End Before 18 Through

• Emancipation. A child aged 16 or older may petition for emancipation by demonstrating financial independence and the ability to live independently. Emancipation terminates parental support obligations.
• Marriage. Minors over 16 can marry with parental permission in Illinois, which terminates the support obligation.
• Military service. Joining the armed forces with parental consent (for those under 18) ends the support obligation.
• Termination of parental rights. Only the state can petition to terminate parental rights by proving the parent is unfit. A parent cannot sign away rights solely to avoid paying child support.

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