Illinois Child Support — Calculator, Laws & Guide (2026)

Understanding Illinois child support laws helps both custodial and non-custodial parents know their rights and obligations. This comprehensive Illinois child support guide covers how payments are calculated, what income counts, when support can be modified, and how orders are enforced. Whether you are going through a divorce, seeking a modification, or dealing with non-payment, this guide explains Illinois’s child support system in plain language.

Verified against Illinois statutes and federal OCSE guidelines as of April 2026.

Illinois Child Support Overview

Illinois uses the income shares model for calculating child support. This model is based on the principle that children should receive the same proportion of parental income they would have received if the family were intact. Both parents’ incomes are combined, and the support obligation is divided proportionally.

Both parents’ monthly net incomes are calculated and combined. The combined net income is looked up in the Schedule of Basic Child Support Obligations (published by HFS, most recently updated March 5, 2025) to find the base obligation for the number of children. Each parent’s share is then allocated proportionally based on their percentage of the combined net income. If shared parenting applies (each parent has 146 or more overnights per year), the basic obligation is multiplied by 1.5 and a separate shared-care formula is used. Healthcare premiums for the children and work-related childcare costs are added to the base obligation and divided proportionally.

How Illinois Calculates Child Support

The Illinois child support calculation considers multiple factors:

1. Determine each parent’s gross income — wages, salary, commissions, bonuses, self-employment income, investment income, and other sources.
2. Calculate combined parental income — add both parents’ adjusted gross incomes together.
3. Apply the guideline schedule — Illinois’s guidelines provide a base support amount based on combined income and number of children.
4. Prorate between parents — each parent’s share is proportional to their percentage of the combined income.
5. Add healthcare and childcare costs — these are added to the base amount and divided proportionally.
6. Apply adjustments — parenting time credits, other child obligations, and special circumstances may adjust the final amount.

Online calculator: Use our child support estimator below to calculate your estimated obligation.

What Counts as Income in Illinois

Net income. Gross income from all sources — wages, salaries, commissions, bonuses, self-employment earnings, pensions, Social Security benefits, unemployment compensation, disability payments, rental income, investment returns, and all other income — minus the following standardized deductions: federal and state income taxes, FICA (Social Security and Medicare), mandatory retirement contributions, union dues, and prior existing child support obligations for other children. Illinois uses a Gross to Net Income Conversion Table (annually updated, most recent effective March 5, 2025) to standardize the net income calculation.

Imputed income: YES. If a parent is voluntarily unemployed or underemployed, the court calculates child support based on potential income. The court considers employment history, job skills, educational attainment, literacy, age, health, criminal record, other employment barriers, record of seeking work, local job market, local employers, and prevailing earnings in the community. If insufficient work history exists, there is a rebuttable presumption that potential income equals 75% of the federal poverty guidelines for a family of one. Imputation requires an evidentiary hearing or agreement of the parties and must be accompanied by specific written findings. Incarceration is NOT considered voluntary unemployment under Illinois law.

Deviation factors: The court may deviate from guidelines if application would be inequitable, unjust, or inappropriate. Specific factors include: (A) extraordinary medical expenditures necessary to preserve life or health of a party or child; (B) additional expenses for a child with special medical, physical, or developmental needs; (C) the financial resources and needs of both parents; (D) the standard of living the child would have enjoyed had the marriage not been dissolved; (E) the physical, emotional, and educational needs of the child; (F) shared parenting time arrangements. Any deviation requires written findings specifying the reasons and the presumed guideline amount without deviation.

Healthcare & Childcare in Illinois Child Support

Health insurance: The court orders one parent (typically whoever can obtain coverage at more reasonable cost) to maintain health insurance for the child. The cost of the child’s health insurance premium is factored into the support calculation. The basic child support obligation already includes an allowance of 250 per child per year for ordinary unreimbursed medical expenses. Unreimbursed medical costs exceeding that 250 threshold are divided between parents proportionally based on their respective shares of combined net income.

Childcare costs: Work-related and education-related childcare costs are added to the basic child support obligation and divided proportionally between parents based on their income shares. Childcare expenses must be reasonable and necessary to enable a parent to maintain employment or pursue education that improves employment opportunities.

When Does Illinois Child Support End?

In Illinois, child support generally ends when the child reaches 18, but if the child has not yet graduated from high school by age 18, support continues until the earlier of high school graduation or age 19. Support also terminates upon the child’s emancipation, marriage, or entry into military service.. However, support may continue or end earlier based on:

• The child graduates from high school (if still a minor)
• The child becomes emancipated (marriage, military service, self-supporting)
• The child has special needs requiring ongoing support
• College support: YES. Under 750 ILCS 5/513, Illinois courts may order one or both parents to contribute to post-secondary educational expenses for non-minor children. Covered expenses include tuition, fees, housing, books, medical insurance, and other reasonable education-related costs. This is a separate obligation from basic child support and may be ordered even after the child turns 18. The court considers factors including the financial resources of both parents and the child, the standard of living the child would have enjoyed, and the child’s academic performance.

Modifying Illinois Child Support

When to modify: A substantial change in circumstances is required. Illinois uses a 20% or more change (increase or decrease) in the support amount as a benchmark for substantial change. Examples include significant change in either parent’s income, job loss, new employment, loss of maintenance obligation, birth of other children, or significant change in parenting time. Additionally, either parent may request a review every 3 years (full 36 months) from the date of the last order.

How to modify: Two pathways: (1) Through the Illinois Division of Child Support Services (DCSS) under the Department of Healthcare and Family Services (HFS) — parents can request an administrative review for modification, available every 36 months or upon substantial change; contact DCSS at 800-447-4278 or [email protected]. (2) Through the circuit court by filing a petition to modify the child support order, which requires showing a substantial change in circumstances. Modifications take effect only from the date the petition is filed, not retroactively to when the change occurred.

Either parent can request a modification. Changes are typically not retroactive to before the date of filing the modification request.

Illinois Child Support Enforcement

Illinois has multiple tools to enforce child support orders when a parent fails to pay:

• Income Withholding Orders (wage garnishment) sent directly to employer; federal and state tax refund interception; driver’s license suspension (after 90+ days of missed payments); professional license suspension through the Illinois Department of Financial and Professional Regulation (after 90+ days); passport denial for arrears exceeding 2500; bank account seizure through Financial Institution Data Match (FIDM) program with liens or levies on accounts; credit bureau reporting; contempt of court proceedings (civil or criminal); liens on real and personal property; lottery winnings interception; workers’ compensation and insurance settlement interception

Contact Division of Child Support Services (DCSS) under the Illinois Department of Healthcare and Family Services (HFS) at https://hfs.illinois.gov/childsupport.html for enforcement assistance.

Additional Illinois rules: Shared parenting calculation: when each parent has 146 or more overnights per year, the basic child support obligation is multiplied by 1.5 and a shared-care formula applies. Illinois annually updates both the Gross to Net Income Conversion Table and the Schedule of Basic Child Support Obligations (since 2024; most recent update effective March 5, 2025). A quadrennial review of the child support guidelines is due in 2026. The Self-Sufficiency Reserve protects low-income obligors: if an obligor’s net income falls below 75% of the federal poverty level for a single person, the minimum support order is 40 per month per child. Incarceration cannot be treated as voluntary unemployment for child support purposes.

Official Sources & Resources

• Division of Child Support Services (DCSS) under the Illinois Department of Healthcare and Family Services (HFS): https://hfs.illinois.gov/childsupport.html
• Federal OCSE: acf.hhs.gov/css
• Cornell LII — Child Support: law.cornell.edu
• Illinois Guidelines Statute: 750 ILCS 5/505 (Child Support) within the Illinois Marriage and Dissolution of Marriage Act (750 ILCS 5/); educational expenses under 750 ILCS 5/513; modification under 750 ILCS 5/510

Last verified April 2026. Contact us if you notice outdated information.

Estimate Your Child Support

Use our free child support estimator to calculate estimated monthly payments. Enter both parents’ incomes, number of children, and custody arrangement to see a personalized breakdown based on your state’s formula.

Related Guides

• Illinois Divorce Process Guide
• Illinois Child Custody Guide
• Illinois Alimony Guide
• All Child Support Guides