How Child Support Is Calculated in Illinois

Since July 1, 2017, Illinois has used the Income Shares model: both parents' net incomes are combined, a schedule sets the basic support amount, and each parent pays their percentage share. If each parent has the child at least 146 overnights a year, a shared physical care calculation (basic amount times 1.5, offset between parents) applies. The Department of Healthcare and Family Services (HFS) publishes the guidelines, worksheets, and an online estimator.

Enroll with Illinois Child Support Services (CSS), part of the Department of Healthcare and Family Services (HFS). Enrollment is free and services are available at no cost to parents or caretakers of a minor child. If you do not have an open case, enroll online through the Child Support eServices portal ("How do I enroll for child support services" and then Enroll); CSS will notify you by email or letter when the case is opened or why it could not be. A closed case requires a new enrollment form. Help is available from the CSS Customer Service Call Center (TTY 1-800-526-5812) or a CSS regional office. CSS does not handle divorce, custody or visitation, or college-expense orders.

Every support order must state a termination date, which can be no earlier than the child's 18th birthday. If the child will not graduate from high school until after turning 18, the termination date can be no earlier than the high school graduation date or the child's 19th birthday, whichever comes first. The termination date does not erase unpaid arrears, and an order can be ended earlier if the child is otherwise emancipated. Separately, a court may order support for a child of the parties who has reached majority and is mentally or physically disabled and not otherwise emancipated; the request can be made before or after the child turns 18. Courts can also order contributions to college or other post-high-school education expenses under a separate section.

A court can modify child support, for payments due after notice of the motion, upon a showing of a substantial change in circumstances. In cases receiving state child support enforcement services, an order can also be changed without showing a substantial change if at least 36 months have passed since it was entered or last modified and the guideline amount differs from the current order by at least 20% (and at least $10 a month), or if the child's health care needs must be addressed. Either parent or a guardian can petition the court or ask CSS for a free review; CSS cases are reviewed every three years and, as a rule, a 20% increase or decrease is required. Request a review by calling 888-245-1938 or using CSS's online modification form.

Once an order is entered, CSS issues an income withholding order to the paying parent's employer. If support is not paid, CSS remedies include tax refund offset, passport denial, denial or suspension of driver's, hunting, fishing and professional licenses, liens on bank accounts and property, and collection from unemployment insurance benefits. CSS also connects paying parents with employment and support programs to remove barriers to payment.

The Illinois Department of Healthcare and Family Services (HFS), Child Support Services, is the state child support agency. Its eServices portal (eservices.epic.hfs.illinois.gov, using an ILogin account) lets parents view case status and payment history, upload documents, update contact information and receive notifications; the site also offers a child support calculator, modification requests, regional office information and a Make a Payment page. Customer service: 800-447-4278; email hfs.dcssconnect@illinois.gov.

The Illinois Department of Healthcare and Family Services (HFS), Division of Child Support Services, publishes the Illinois Child Support Estimator, "designed to provide a general idea of a child support amount based on the Illinois child support guidelines (750 ILCS 5/505)." HFS says it "is for informational purposes only," that your result "may not be the same amount that the Department or the court may establish," and that it "is not a guarantee of the amount of child support awarded."