Child support in Illinois
Illinois uses the income-shares model: both parents' incomes count, and each parent pays a share of the child's support. To open a case, contact the Illinois Department of Healthcare and Family Services (HFS), Child Support Services (CSS) at 1-800-447-4278.
Checked against official sources: Oct 25, 2026. · Free letters and checklist ↓
How much child support in Illinois?
Both parents' net incomes (usually a standardized net income based on ordinary taxes) are added together and looked up in the state schedule to find the basic support obligation. Each parent pays a share based on their part of the combined income. Work-related child care can be added. If each parent has 146 or more overnights a year, a shared physical care formula is used.
Law: 750 ILCS 5/505
We don't estimate Illinois's amount here: its formula uses both parents' incomes and other facts, and a home-made number could mislead you. The official tool gives the real starting number:
Open a child support case in Illinois
- Phone
- 1-800-447-4278 (TTY 1-800-526-5812)
- Apply
- Apply online
- How to open a case
Enroll for Child Support Services online through the Child Support eServices portal, by calling 1-800-447-4278, or at a CSS regional office. CSS can establish parentage, get a child and medical support order through the agency or the circuit court, and send income withholding to the employer. You can also ask the circuit court for support using the statewide forms.
- Application fee
$0. HFS says enrolling for Child Support Services is free and services are available at no cost to parents or caretakers.
- Forms
- Paternity (legal fatherhood)
Unmarried parents can sign the Illinois Voluntary Acknowledgment of Parentage. When signed, witnessed and filed with HFS, it establishes parentage without court; the parent can be a genetic parent or an intended parent through assisted reproduction (not surrogacy). CSS can also help with genetic testing.
Source: VAP, form HFS 3416B
Illinois child support by topic
How support is calculated in Illinois
The model, the percentages or the official calculator, and low-income rules.
Change child support in Illinois
When you can ask, how to ask, and a review letter.
Collect unpaid support in Illinois
Collection tools, interest and license rules, and a letter.
When support ends in Illinois
The end age, high school and disability rules.
How child support is figured in Illinois
- Model
- Income shares
- How it works
Both parents' net incomes (usually a standardized net income based on ordinary taxes) are added together and looked up in the state schedule to find the basic support obligation. Each parent pays a share based on their part of the combined income. Work-related child care can be added. If each parent has 146 or more overnights a year, a shared physical care formula is used.
- Official calculator
- Official Illinois child support calculator
- Health insurance and medical costs
A support order may say which parent must provide health insurance. CSS sends a medical support notice to the employer to enroll the children in coverage.
Law: 750 ILCS 5/505
Change a child support order in Illinois
- When a change is allowed
Either parent or the child's guardian can ask for a change at any time. CSS reviews its cases every 3 years and, as a rule, needs about a 20% increase or decrease for a change. In court, the judge decides whether there has been a substantial change in circumstances.
- How to ask
Request a free CSS review by calling 1-888-245-1938, using the online modification form, or emailing the Affidavit of Income and Expenses (HFS 2782J) and the Disclosure Statement on Legal Representation (HFS 3304). You must have an open CSS case. If CSS denies your request, you can still go to court yourself.
Law: 750 ILCS 5/510
Can I ask for a change? Check your situation
Collect unpaid child support in Illinois
Arrears means support that is past due. The child support agency can use these tools to collect it:
- Collection tools
- Income withholding (including unemployment benefits)
- Federal and state tax refund intercept
- Comptroller offset
- Passport denial or revocation
- Driver's license suspension
- Professional and hunting/fishing license suspension
- Credit bureau reporting
- Liens on bank accounts, real estate, personal property and lawsuit settlements
- Offset of lottery and casino winnings
- Contempt of court
CSS does not jail parents for not paying, but a judge can order jail after finding a parent in contempt for not following a support order.
Source: HFS FAQ
- Interest on unpaid support
By law, support more than 30 days past due carries interest at 9% a year. Since January 1, 2021, CSS no longer calculates or enforces interest unless a court has ordered it, but you may still owe court-ordered interest. At the end of a case, you can ask HFS in writing to have interest adjudicated.
Law: 0.75% a month; 89 Ill. Adm. Code 160.89
Source: HFS FAQ
Law: 750 ILCS 5/505
When child support ends in Illinois
- Support ends
18, or up to 19 if the child is still in high school
- Exceptions
Support can continue past 18 for a child found permanently disabled before age 18. A court can order help with college expenses under a separate law, but CSS does not handle college-expense orders.
Law: 750 ILCS 5/505; 750 ILCS 5/513
When does support end? Check your situation
Free help in Illinois
- Illinois Legal Aid Online
- Illinois State Bar Association Illinois Lawyer Finder
- Find free legal help at LawHelp.org
Official self-help
Free letters and checklist
Ask the agency to review (change) your order
A letter to the child support agency asking for a review and adjustment.
Ask the agency to collect unpaid support
A letter asking the agency to enforce the order and collect what is past due.
Checklist: what to bring to open a case
IDs, birth certificates, the other parent's details and your papers, with Illinois's agency contact.
Good to know in Illinois
- Illinois uses a standardized net income figure; a parent can ask the judge to use an individualized net income instead (HFS Income Shares FAQ).
- With 146 or more overnights each, the basic obligation is multiplied by 1.5 and shared by each parent's time (HFS Income Shares FAQ).
- HFS has a new Child Support eServices portal where you can enroll, see payments and upload orders (HFS).
Changes in 2024–2026
The HFS Child Support Estimator page was revised March 20, 2026; HFS says the estimator reflects 2024 state and federal income withholding levels and the 2024 federal poverty guideline for one person.
Federal rules in every state
- Applying. If you don't get TANF, Medicaid or foster care help, a state may charge an application fee of up to $25 to open a child support case. Law: 42 U.S.C. 654(6)(B)(i)
- Yearly fee. If you never got TANF and the agency collected at least $550 for you in a year, the state charges a $35 yearly fee. It can come out of your support, but never out of the first $550. Law: 42 U.S.C. 654(6)(B)(ii)
- Review every 3 years. If your case is with the child support agency, either parent can ask it to review the order every 3 years and adjust it to the guidelines. Law: 42 U.S.C. 666(a)(10)(A); 45 CFR 303.8
- Past-due support. Each unpaid payment becomes a judgment on the day it is due. It can't be lowered later, except back to the date the other parent got notice of a request to change the order. Law: 42 U.S.C. 666(a)(9)
- Tax refunds. The federal government can take a federal tax refund to pay past-due child support. Law: 42 U.S.C. 664
- Passports. A parent who owes more than $2,500 in past-due support can be refused a passport. Law: 42 U.S.C. 652(k)
- Pay withholding limit. For support, up to 50% of take-home pay can be withheld if the parent supports another spouse or child, or 60% if not. It is 55% or 65% when support is more than 12 weeks behind. Law: 15 U.S.C. 1673(b)
- How long support lasts. How long support lasts follows the law of the state that made the order, even if you move. Law: 28 U.S.C. 1738B(h)(2)
Questions about child support in Illinois
How is child support calculated in Illinois?
Both parents' net incomes (usually a standardized net income based on ordinary taxes) are added together and looked up in the state schedule to find the basic support obligation. Each parent pays a share based on their part of the combined income. Work-related child care can be added. If each parent has 146 or more overnights a year, a shared physical care formula is used.
Is there an official child support calculator for Illinois?
How do I apply for child support in Illinois?
Enroll for Child Support Services online through the Child Support eServices portal, by calling 1-800-447-4278, or at a CSS regional office. CSS can establish parentage, get a child and medical support order through the agency or the circuit court, and send income withholding to the employer. You can also ask the circuit court for support using the statewide forms.
Does it cost money to open a child support case in Illinois?
$0. HFS says enrolling for Child Support Services is free and services are available at no cost to parents or caretakers.
When can child support be changed in Illinois?
Either parent or the child's guardian can ask for a change at any time. CSS reviews its cases every 3 years and, as a rule, needs about a 20% increase or decrease for a change. In court, the judge decides whether there has been a substantial change in circumstances.
How do I ask to change child support in Illinois?
Request a free CSS review by calling 1-888-245-1938, using the online modification form, or emailing the Affidavit of Income and Expenses (HFS 2782J) and the Disclosure Statement on Legal Representation (HFS 3304). You must have an open CSS case. If CSS denies your request, you can still go to court yourself.
What happens if child support is not paid in Illinois?
Arrears means support that is past due. The child support agency can use these tools to collect it: Income withholding (including unemployment benefits); Federal and state tax refund intercept; Comptroller offset; Passport denial or revocation; Driver's license suspension; Professional and hunting/fishing license suspension; Credit bureau reporting; Liens on bank accounts, real estate, personal property and lawsuit settlements; Offset of lottery and casino winnings.
Can a parent be held in contempt for not paying in Illinois?
CSS does not jail parents for not paying, but a judge can order jail after finding a parent in contempt for not following a support order.
Is there interest on unpaid child support in Illinois?
By law, support more than 30 days past due carries interest at 9% a year. Since January 1, 2021, CSS no longer calculates or enforces interest unless a court has ordered it, but you may still owe court-ordered interest. At the end of a case, you can ask HFS in writing to have interest adjudicated.
When does child support end in Illinois?
18, or up to 19 if the child is still in high school
Does child support continue while my child finishes high school in Illinois?
18, or up to 19 if the child is still in high school
Can child support continue past the usual age in Illinois?
Support can continue past 18 for a child found permanently disabled before age 18. A court can order help with college expenses under a separate law, but CSS does not handle college-expense orders.
How is paternity established in Illinois?
Unmarried parents can sign the Illinois Voluntary Acknowledgment of Parentage. When signed, witnessed and filed with HFS, it establishes parentage without court; the parent can be a genetic parent or an intended parent through assisted reproduction (not surrogacy). CSS can also help with genetic testing.
Who pays for the child's health insurance in Illinois?
A support order may say which parent must provide health insurance. CSS sends a medical support notice to the employer to enroll the children in coverage.
More help on our sister sites
Sources
- HFS: Enroll for services
- HFS: Modifications
- HFS: Child support FAQs
- HFS: Child Support Estimator
- HFS: Income Shares FAQ
- Illinois Courts: Divorce, child support and maintenance forms
Last checked: Oct 25, 2026.
- State plan requirements: application fee, annual fee, safeguards, 42 U.S.C. 654
- Required state laws: arrears as judgments, review every 3 years, UIFSA, 42 U.S.C. 666
- Federal tax refund offset, 42 U.S.C. 664
- Passport denial for child support arrears, 42 U.S.C. 652(k)
- Garnishment limits for support orders, 15 U.S.C. 1673(b)
- Full faith and credit for child support orders, 28 U.S.C. 1738B
- Office of Child Support Enforcement (federal)