The Basics of Illinois Child Support Every Divorcing Parent Should Know

 Posted on July 30, 2026 in Allocation of Parental Responsibilities

When a couple gets divorced, child support makes sure both parents continue to help pay for what their children under age 18 need. The parent with less parenting time often makes payments to the parent who provides most of the day-to-day childcare. However, parenting time alone does not determine who pays child support, or how much the payments are.

To calculate child support, Illinois uses a formula that considers both parents’ incomes, the number of children, and the parenting arrangements. The court may also divide expenses for health insurance, childcare, school and medical needs, all of which expenses are not covered by child support.

If you are getting divorced in 2026 and have questions about child support, or any other aspect of your divorce, our Oak Park child support attorney can explain what the guidelines require in your case.

When Does Child Support Begin During an Illinois Divorce?

Parents do not always have to wait until the divorce case is finished before child support payments can begin. Children still need food, housing, healthcare and other necessities during the case.

Under 750 ILCS 5/501, either parent may ask the court for temporary child support while the divorce is pending. A temporary order remains in place unless or until the court changes it, or replaces it with a final support order.

If a parent is already providing financial support during a divorce, that parent should keep accurate records of those payments. Bank transfers, checks and electronic payment records provide much better evidence than cash. 

How Does Illinois Calculate Child Support?

Illinois uses what is called the "income shares model" under 750 ILCS 5/505. This is a formula that combines both parents’ net monthly incomes, and then uses a schedule of basic child support obligations to determine payments. The formula then divides that obligation between the parents according to each parent’s share of the combined net income.

A parent’s income may include more than just a paycheck. Income includes not only wages, but also bonuses, commissions, unemployment benefits, and more.

The court may also calculate a party’s potential income when that parent is voluntarily unemployed, or even underemployed. As a result, a parent cannot just avoid paying child support by quitting a job to make his or her income appear lower.

Does Parenting Time Affect Child Support in Illinois?

Under the current version of 750 ILCS 5/505, the "shared parenting calculation" applies when each parent has at least 146 overnights with the child each year. This calculation increases the combined basic obligation to recognize that both households are responsible for supporting the child, and then adjusts each parent’s share according to income and parenting time.

A nearly equal parenting time schedule does not guarantee that no child support will be paid. When one parent earns considerably more than the other, that parent may still owe child support despite having close to half of the overnights.

What Expenses Can Be Added to Basic Child Support?

The guideline amount does not always cover every child-related expense. Under 750 ILCS 5/505, the court may also allocate expenses such as:

• Health insurance premiums;

• Uninsured medical expenses;

• Work-related childcare;

• Educational expenses; and,

• Extracurricular activity costs.

The court order should explain which parent pays each expense and how shared costs will be divided. Parents may divide expenses equally, or according to their incomes.

Making clear, specific agreements in a child support court order is important for preventing future disputes. An order can be very specific, even stating when receipts must be provided, how reimbursement requests should be sent, and how quickly the other parent must pay his or her part of a shared expense. 

Can a Judge Order a Child Support Amount Different From the Guidelines Figure?

The Illinois child support guidelines create what’s known as "a rebuttable presumption". That means the court starts with the guideline amount, but may deviate when applying it would be "inequitable, unjust or inappropriate."

A judge considering a deviation may look at:

• The child’s financial needs;

• Each parent’s financial resources;

• The child’s physical, emotional and educational needs; and,

• The standard of living the child would have had if the marriage had continued.

A parent who wants a deviation needs to provide evidence supporting their request, rather than simply claiming that the guideline number is unfair. Tax returns, pay records, medical bills, school costs, and/or proof of unusual household expenses might be used as evidence for either greater or lesser child support payments. 

How Long Does Child Support Last in Illinois?

Child support normally continues until a child turns 18. When the child turns 18 while still in high school, support generally continues until graduation or age 19, whichever happens first. The support order should state a termination date. 750 ILCS 5/510 also provides for termination upon emancipation in certain circumstances.

When parents have multiple children, the order will likely have a schedule reducing support as each child turns 18. Still, parents need to review the language of the order rather than stopping payments without notice.

Illinois law also allows the court to order contributions toward college or other educational expenses. Those expenses are separate from ordinary child support, and do not continue automatically.

When Can Child Support Be Changed?

Either parent may request a child support modification after "a substantial change in circumstances" by filing a petition with the court. Modifications generally affect payments made after the other parent receives notice of the petition. Waiting several months to file may mean losing the chance to change payments for that earlier period.

Illinois also allows certain cases handled through the Department of Healthcare and Family Services to be reviewed without proof of a substantial change when at least 36 months have passed.

What Happens if a Parent Does Not Pay Child Support?

Child support does not become optional because a parent loses a job, disagrees with the parenting schedule, believes the amount is too high, or any other reason. The existing order is enforceable until the court changes it.

A parent who genuinely cannot make the required payments should petition the court for a modification quickly. Ignoring the order allows unpaid child support to add up, sometimes accumulating interest. 

The parent receiving support should also remember that unpaid child support and denied parenting time are separate legal issues. Under the law, a parent cannot withhold parenting time to punish nonpayment of child support.

Contact an Oak Park, IL Child Support Attorney

Child support can affect your finances and your children’s quality of life for years after a divorce. Our experienced Hillside child support lawyer at the Law Office of Vincent C. Machroli, P.C. helps parents understand how child support works in Illinois, while advocating for fair payments and a favorable divorce decree.

With more than 39 years of legal experience, we are here to help whenever you’re ready. Call 708-449-7404 to schedule a no-charge legal consultation.