Key takeaways:
- Illinois uses the income shares model: support is based on both parents’ combined net income and the number of children, then split by each parent’s share of that income.
- You do not need to receive public assistance to get help. Illinois HFS Child Support Services is free to enroll in and can establish parentage, set up an order, withhold wages and enforce payment.
- Payments run through the Illinois State Disbursement Unit (SDU). Employers must send withheld support to the SDU within 7 business days of payday.
- From January 1, 2027, Public Act 104-733 lowers the shared-care threshold from 146 to 110 overnights and raises the income limit for the $40 minimum order. Existing orders do not change on their own.
Last reviewed: October 22, 2026. This article is general information about Illinois law, not legal advice. Laws change and every situation is different, so talk to a licensed attorney in your state about your own case.
Child support in Illinois has two sides: the math that sets the amount, and the practical system that gets money from one household to the other. This guide focuses on the practical side, statewide: how to open a case, what you need, how payments move, and what happens when they stop. For a deeper walk-through of the formula and local court information, see our Rockford child support guide.
Contents
- How the amount is set, in brief
- Two ways to start a case
- Establishing parentage
- What to gather
- How payments work
- When payments stop
- Changing the amount
- FAQ
How the amount is set, in brief
Under 750 ILCS 5/505, the court (or HFS) finds each parent’s net income, adds them together, and looks up a basic support amount on the HFS income shares schedule for that combined income and number of children. Each parent owes their percentage share. The parent with fewer overnights pays their share to the other parent.
- Shared care: under current law, if each parent has 146 or more overnights a year, a shared-care formula applies (the basic amount is multiplied by 1.5, then split and offset).
- Low incomes: a parent at or below 75% of the federal poverty guideline for one person is presumed to owe a minimum of $40 per month per child, with a $120 monthly maximum across all their children. A $0 order is presumed for a parent with no income other than means-tested benefits, or who cannot work because of a medically proven disability, incarceration or institutionalization.
- Add-ons: health insurance, uncovered medical costs, child care and some school and extracurricular expenses can be divided between the parents.
Get a baseline: the HFS child support estimator gives an estimate from the official schedules. Only a court or administrative order makes an amount binding.
What changes on January 1, 2027
| Topic | Until Dec 31, 2026 | From Jan 1, 2027 (P.A. 104-733) |
|---|---|---|
| Shared physical care | 146+ overnights each | 110+ overnights each, with a graduated adjustment from 10% (110 to 114 overnights) down to 2% (140 to 145) |
| $40 minimum order applies at | Up to 75% of the federal poverty guideline | Up to 100% of the federal poverty guideline |
| Incarceration over 180 days | Parent must ask for a modification | A notice of incarceration can reduce support to $0 if no one objects within 45 days |
The new law itself is not a substantial change in circumstances. To apply the new rules to an existing order, a court must find a substantial change that warrants it.
Two ways to start a case
1. Through HFS Child Support Services (CSS). Services are available at no cost to parents or caretakers of a minor child, whether or not you receive public assistance. You enroll online through the HFS eServices portal. CSS can locate a parent, establish parentage, obtain child and medical support orders, serve income withholding orders, and collect and enforce support. It does not handle divorce, custody or parenting time.
2. Through the circuit court. Child support is usually decided as part of a divorce, parentage or allocation of parental responsibilities case filed with the circuit clerk in your county. If you cannot afford the filing fee, you can apply for a fee waiver.
The two routes can work together. For example, a court can enter the order and HFS can still help with collection and enforcement.
Establishing parentage
If the parents were not married when the child was born, legal parentage has to be established before a support order can be entered. There are two main ways:
- Voluntary Acknowledgment of Parentage (VAP). Under the Illinois Parentage Act of 2015 (750 ILCS 46/301), both parents can sign and witness a VAP, often at the hospital, though it can also be done later. There is no filing fee. A signer can rescind it within 60 days (or earlier, if a court proceeding involving the child starts sooner). After that, it can only be challenged in limited circumstances.
- Genetic testing and an order. If parentage is disputed, HFS or the court can order genetic testing. HFS says testing is at no cost to you when it handles the case.
Legal parentage matters beyond support: it can affect inheritance, benefits and the other parent’s ability to seek parenting time.
What to gather
- The child’s birth certificate and any VAP or parentage order
- Any existing divorce judgment, support order or parenting plan
- Your recent pay stubs and tax returns
- What you know about the other parent: full name, address, employer and, if you have it, Social Security number
- Records of child care, health insurance and medical costs for the child
Missing information does not stop you from enrolling, but it can slow down locating the other parent or setting the amount.
How payments work
Support is processed by the Illinois State Disbursement Unit (SDU), so every payment is recorded. The most common method is income withholding: an income withholding notice is sent to the paying parent’s employer, which deducts support from each paycheck.
- The employer must start withholding no later than the next payday that occurs 14 days after the notice is sent.
- The employer must pay withheld amounts to the SDU within 7 business days after payday. An employer that knowingly fails to do so faces a penalty of $100 per day, up to $10,000 per occurrence (750 ILCS 28/35).
- Parents who are not on withholding can pay by bank withdrawal, card, MoneyGram, mail (checks or money orders payable to the Illinois State Disbursement Unit) or at a regional office. See the HFS payment options.
Protect your account. Use only the official HFS eServices portal and phone numbers listed on hfs.illinois.gov. Do not share your login details with anyone who contacts you unexpectedly, and keep your mailing address current so you receive notices.
If your family has received cash assistance (TANF), some or all of the support collected may go to the state as reimbursement. Ask CSS how this applies to your case.
When payments stop
Unpaid support becomes a judgment and accrues interest. Through CSS or the court, collection tools listed by HFS include:
- intercepting federal and state tax refunds;
- suspending driver’s, professional or recreational licenses and denying a passport;
- reporting to credit bureaus;
- liens on bank accounts, real estate, personal property and lawsuit settlements;
- offsets of lottery or casino winnings.
You can also file a petition with the court asking it to hold the other parent in contempt. Support generally continues until the child turns 18, or until the earlier of high school graduation or age 19 if the child is still in high school.
Changing the amount
Changes are never automatic. Either parent can ask the court to modify support after a substantial change in circumstances, such as a job loss, a big raise or a change in parenting time. A modification generally applies only to payments due after the other parent receives notice of the request, so it is better not to wait.
In cases handled by HFS, there is an extra route. HFS says CSS cases are reviewed every three years, or sooner after a significant change, and that a change of about 20% is generally required. Under 750 ILCS 5/510, in HFS cases where at least 36 months have passed since the order was entered or last modified, a difference of at least 20% (and at least $10 a month) from the guideline amount allows a modification without proving a substantial change. You can request a review through the HFS modification page.
FAQ
Do I have to be on public assistance to get help from HFS?
No. HFS Child Support Services are available at no cost to parents or caretakers of a minor child, and enrollment is free and done online.
How fast does an employer have to send withheld support?
Under 750 ILCS 28/35, the employer must pay withheld support to the State Disbursement Unit within 7 business days after the payday on which it was withheld.
Can child support be reviewed every three years in Illinois?
In HFS cases, yes. HFS says CSS cases are reviewed every three years or sooner after a significant change. Outside HFS, you ask the court to modify support based on a substantial change in circumstances.
Does the 2027 law change my existing order?
Not automatically. You would need to ask for a modification, and the court must find a substantial change in circumstances. The new incarceration notice procedure is the main exception.
Sources: 750 ILCS 5/505; 750 ILCS 5/510; Public Act 104-733; 750 ILCS 28/35 (income withholding); 750 ILCS 46/301 (voluntary acknowledgment); HFS: services and enrollment; HFS child support FAQ; HFS modifications.
