Illinois Child Support Laws (2026): Guidelines & Calculator

Illinois calculates child support using the Income Shares Model under 750 ILCS 5/505, which considers the combined net income of both parents. Courts look up the total obligation on a schedule based on combined income and number of children, then assign each parent a share proportional to their contribution to that combined income. Use the Illinois child support calculator below to estimate a guideline amount, or open the full-page Illinois child support calculator to explore different income scenarios.

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 due 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:

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.

This threshold drops to 110 overnights on January 1, 2027. Public Act 104-0733, signed on July 31, 2026, rewrites the shared physical care provision in 750 ILCS 5/505(a)(3.8) so that shared physical care means each parent exercises 110 or more overnights per year, or 110 or more overnight equivalents. The 1.5 multiplier stays. The Act also adds a sliding adjustment for parents between the new and old thresholds: where a parent has shared physical care for fewer than 146 overnights, that parent's shared care obligation is increased by a set percentage, running from 10% at 110 to 114 overnights down to 2% at 140 to 145 overnights. Until January 1, 2027, the 146-overnight rule described above remains the operative law.

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.

Under 750 ILCS 5/505, courts can assign an income figure to a parent who chooses not to work or works below their earning capacity. A court may deny a modification request if the petitioning parent is found to be voluntarily reducing income to lower their support obligation.

Recent Changes to Illinois Child Support Laws

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

2026 Schedule Update

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 20, 2026. Since 2024, Illinois updates both tables annually, whereas previously only the Gross to Net table received yearly updates.

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 further updates to obligation amounts.

2021 Interest Policy Change

Illinois changed its interest policy on child support arrears effective January 1, 2021, through Public Act 101-0336. The state no longer automatically charges interest on past-due balances. Interest is now only assessed when specific criteria are met, typically after the youngest child is emancipated and remaining balances are under review. When interest is adjudicated, the rate remains 9% annually. This change makes it easier for parents with back support to catch up on payments.

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

A narrower route allows modification without proving a substantial change when 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. This path is limited by statute. Under 750 ILCS 5/510(a)(2)(A), it applies only in cases where a party is receiving child support enforcement services from the Department of Healthcare and Family Services under Article X of the Illinois Public Aid Code, and only when at least 36 months have elapsed since the order was entered or last modified. Parents whose orders are private and not enforced through the state agency must use the substantial change route described above.

The ground also does not apply where the inconsistency exists because the existing order itself resulted from a deviation from the guideline amount and there has not been a change in the circumstances that produced that deviation.

A separate provision, 750 ILCS 5/510(a)(2)(B), allows modification without a substantial change upon a showing of a need to provide for the child's health care needs through health insurance or other means.

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. Support stays at the old amount until the other parent has notice of the petition, so get a free case evaluation from an Illinois family lawyer and file and serve it as soon as your circumstances change (attorney advertising).

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

Criminal Penalties Under the Non-Support Punishment Act

Under the Non-Support Punishment Act, 750 ILCS 16/15, failure to pay child support can result in criminal prosecution:

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.

More Illinois Laws

• Illinois Alimony Laws
• Illinois Child Custody Laws
• Illinois Divorce Laws

Frequently Asked Questions

Do you have to pay child support if you have joint custody in Illinois?

Yes. Even with joint custody (called shared parenting in Illinois), the higher-earning parent typically pays support to the lower-earning parent. When each parent has the child for at least 146 overnights per year, the shared parenting formula applies. The basic support obligation is multiplied by 1.5, and each parent's share is offset against the other. The parent with the higher obligation pays the difference. Note that Public Act 104-0733 lowers that 146-overnight threshold to 110 overnights effective January 1, 2027, and adds a sliding percentage adjustment for parents below 146 overnights.

How often are Illinois child support tables updated?

Since 2024, Illinois updates both the Gross to Net Income Conversion Table and the Schedule of Basic Child Support Obligations on an annual basis. The most recent update took effect March 20, 2026. A broader quadrennial review of the entire guideline framework is due for completion in 2026.

Can child support be modified if I lose my job in Illinois?

Yes. Involuntary job loss qualifies as a substantial change in circumstances under 750 ILCS 5/510. However, you need to petition for modification promptly because support continues at the original amount until a court officially modifies the order. The modification takes effect from the date the other parent receives notice of the petition, not before.

Does Illinois require parents to pay for college expenses?

Illinois courts can order parents to contribute to college and post-secondary educational costs under 750 ILCS 5/513. Contributions are capped at the cost of attending the University of Illinois at Urbana-Champaign. The child must maintain at least a C average, and payments end no later than age 23 (or 25 with good cause). Courts weigh both parents' finances, the child's academic record, and available scholarships.

What happens if a parent refuses to pay child support in Illinois?

Illinois has extensive enforcement tools. The state can garnish wages, seize bank accounts, suspend driver's and professional licenses, intercept tax refunds, deny passports, and report delinquencies to credit bureaus. If arrears exceed $5,000 or support goes unpaid for more than six months, a first offense is a Class A misdemeanor carrying up to one year in jail, and a second or subsequent offense is a Class 4 felony. Arrears over $20,000 or nonpayment for more than one year can result in Class 4 felony charges carrying 1 to 3 years in prison.