How to Modify Child Support in Illinois
Reviewed by DocDraft Legal Team · Illinois · Last updated September 21, 2026
In Illinois, a child support modification is a court, or the state child support agency, changing the amount of an existing support order after circumstances change (750 ILCS 5/510). Unlike states with a single numeric court trigger, Illinois gives you two doors. In court, you file a motion to modify and show a substantial change in circumstances since the last order, such as a job loss, a raise, or a new parenting schedule. Separately, if the Department of Healthcare and Family Services handles your case, it can seek a change without proving a substantial change, based on an inconsistency of at least 20 percent, but no less than 10 dollars a month, between the current order and the guideline amount, and only after at least 36 months have passed (750 ILCS 5/510). Illinois sets support with an income shares guideline tied to both parents' net incomes and parenting time (750 ILCS 5/505), so a change in income or time can push the order too high or too low. There is no dedicated statewide modification form; you file a general motion to modify in the circuit court that entered your order. A change reaches back only to installments coming due after the other parent has due notice of your filing, so support already due generally cannot be reduced (750 ILCS 5/510). Keep paying your current order until it is changed. Attorney review of your filing is available through DocDraft.
Find out where you stand in Illinois
Where are you with changing your child support order?
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How do I modify child support in Illinois?
File a motion to modify in the circuit court that entered your order and show a substantial change in circumstances since the last order (750 ILCS 5/510). If the Department of Healthcare and Family Services handles your case, you can instead ask it to review the order for free.
How much does the amount have to change to modify child support in Illinois?
In court, Illinois requires no fixed percentage, only a substantial change in circumstances (750 ILCS 5/510). On the agency path, the Department of Healthcare and Family Services can act when the order and the guideline amount differ by at least 20 percent, but no less than 10 dollars a month, after 36 months.
How far back can a child support change go in Illinois?
A modification reaches only installments coming due after the other parent has due notice of your filing, not back to when your circumstances changed (750 ILCS 5/510). Support that already came due generally cannot be reduced, so filing promptly protects you. Keep paying the current order until a judge changes it.
Which court handles child support modifications in Illinois?
The circuit court in the county that entered your existing order handles modifications, usually in its family or domestic relations division. If the Department of Healthcare and Family Services manages your case, you can also ask its Division of Child Support Services to review and adjust the order without a court hearing.
Illinois child support modification at a glance
In Illinois, a child support modification is a court or the state child support agency changing the amount of an existing support order after circumstances change (750 ILCS 5/510). In court you file a motion to modify and show a substantial change in circumstances since the last order. Separately, if the Department of Healthcare and Family Services handles your case, it can seek a change without that showing when the order and the guideline amount differ by at least 20 percent, but no less than 10 dollars a month, after at least 36 months (750 ILCS 5/510). Support is set by an income shares guideline tied to both parents' net incomes and parenting time (750 ILCS 5/505). There is no dedicated statewide modification form, and a change reaches only installments coming due after the other parent has due notice of your filing.
Using the HFS review after three years and a pay cut
Suppose your Illinois case is handled by the Department of Healthcare and Family Services, your last order is more than three years old, and your income has dropped. Because the agency path needs no proof of a substantial change, you ask its Division of Child Support Services for a modification review, and it checks whether the order and the current guideline differ by at least 20 percent, but no less than 10 dollars a month (750 ILCS 5/510). You can also file a motion to modify in the circuit court. Because a change reaches only installments due after notice of your filing (750 ILCS 5/510), you act promptly and keep paying the current order until it is changed. Attorney review of your filing is available through DocDraft.
Relevant Laws
750 ILCS 5/510 (modification and retroactivity)
Provides that support may be modified only as to installments accruing after due notice by the moving party of the filing of the motion, allows modification on a substantial change in circumstances, and permits a no-fault change on an inconsistency of at least 20 percent, but no less than 10 dollars per month, versus the guideline for cases receiving Department of Healthcare and Family Services services after 36 months.
750 ILCS 5/505 (income shares child support guideline)
Sets Illinois's statewide income shares guideline for calculating child support based on both parents' combined net income and the parenting time each parent exercises, which is the amount a court or the agency compares the existing order against when deciding a modification.
Illinois Department of Healthcare and Family Services, Child Support Services
The state IV-D child support agency, whose Division of Child Support Services can review an existing order at no cost and pursue a modification through the administrative and court process when the guideline inconsistency and time thresholds are met.
Illinois Courts approved forms and self-help
The Illinois Courts website provides the approved motion forms and instructions parents use to file in the circuit court, since Illinois has no dedicated statewide form solely for modifying a child support order.
Regional Variances
Illinois child support modification rules at a glance
Qualifying threshold
In court, a substantial change in circumstances since the last order, with no fixed percentage (750 ILCS 5/510). On the agency path, an inconsistency of at least 20 percent, but no less than 10 dollars a month, versus the guideline, in cases handled by the Department of Healthcare and Family Services after 36 months.
Where to file
The circuit court in the county that entered your existing order, usually its family or domestic relations division. If the Department of Healthcare and Family Services manages your case, you can ask its Division of Child Support Services to review and pursue a change.
Modification form
Illinois has no dedicated statewide form solely for modifying child support. You file a general motion to modify in the circuit court, using the approved motion forms and instructions on the Illinois Courts website, with current income proof for both parents.
Retroactivity
A change reaches only installments accruing after the other parent has due notice of the filing of the motion, not back to when circumstances changed (750 ILCS 5/510). Support that already came due generally cannot be reduced.
Periodic review
If the Department of Healthcare and Family Services handles your case, you can generally request a review about every three years without showing a change, under federal rules, and sooner when a substantial change occurs.
Suggested Compliance Checklist
Gather proof of your changed circumstances
Before you file days after startingCollect current pay stubs, tax returns, and proof of the change (job loss, income change, or a new parenting schedule), and estimate the new guideline amount (750 ILCS 5/505). Attorney review of your filing is available through DocDraft.
Check whether the HFS agency handles your case
Before you file days after startingConfirm whether the Department of Healthcare and Family Services manages your case. If so, you can ask its Division of Child Support Services for a free modification review, which can seek a change on a 20 percent, but no less than 10 dollars a month, guideline gap after 36 months.
Draft your motion to modify child support
As soon as your circumstances change days after startingBecause Illinois has no dedicated statewide modification form, draft a motion to modify for the circuit court that entered your order, state the substantial change in circumstances, and attach income proof. Use the approved motion forms and instructions on the Illinois Courts website.
File with the circuit court
Promptly (the change dates back to notice of filing) days after startingFile your motion with the circuit court clerk and pay the fee, or request a fee waiver. Because a change reaches only installments due after the other parent has due notice of your filing, file promptly (750 ILCS 5/510).
Give the other parent due notice
Before the hearing days after startingServe the other parent with your filed motion and the notice of hearing under the court's rules, then file proof of service. Due notice of your filing fixes the earliest date your change can reach, so complete it correctly and on time (750 ILCS 5/510).
Attend the hearing and get the new order
On your hearing date days after startingGo to the hearing with your income proof and evidence of the change, let the judge recalculate support under the income shares guideline (750 ILCS 5/505), and get the signed order. Keep paying the current order until then.
| Task | Description | Document | Days after starting |
|---|---|---|---|
| Gather proof of your changed circumstances | Collect current pay stubs, tax returns, and proof of the change (job loss, income change, or a new parenting schedule), and estimate the new guideline amount (750 ILCS 5/505). Attorney review of your filing is available through DocDraft. | - | Before you file |
| Check whether the HFS agency handles your case | Confirm whether the Department of Healthcare and Family Services manages your case. If so, you can ask its Division of Child Support Services for a free modification review, which can seek a change on a 20 percent, but no less than 10 dollars a month, guideline gap after 36 months. | - | Before you file |
| Draft your motion to modify child support | Because Illinois has no dedicated statewide modification form, draft a motion to modify for the circuit court that entered your order, state the substantial change in circumstances, and attach income proof. Use the approved motion forms and instructions on the Illinois Courts website. | - | As soon as your circumstances change |
| File with the circuit court | File your motion with the circuit court clerk and pay the fee, or request a fee waiver. Because a change reaches only installments due after the other parent has due notice of your filing, file promptly (750 ILCS 5/510). | - | Promptly (the change dates back to notice of filing) |
| Give the other parent due notice | Serve the other parent with your filed motion and the notice of hearing under the court's rules, then file proof of service. Due notice of your filing fixes the earliest date your change can reach, so complete it correctly and on time (750 ILCS 5/510). | - | Before the hearing |
| Attend the hearing and get the new order | Go to the hearing with your income proof and evidence of the change, let the judge recalculate support under the income shares guideline (750 ILCS 5/505), and get the signed order. Keep paying the current order until then. | - | On your hearing date |
Frequently Asked Questions
A real, involuntary income drop can be a substantial change in circumstances supporting a modification, but you must file a motion to change the amount; support keeps accruing at the old rate until the court acts (750 ILCS 5/510). A judge may weigh whether you are earning what you reasonably could. Do not simply stop paying.
No. Either parent can file a motion to modify on their own, and the other parent receives due notice and can respond (750 ILCS 5/510). If both parents agree on a new amount, they can submit a written agreement for a judge to approve, and the judge still checks it against the guideline (750 ILCS 5/505).
After you file your motion in the circuit court, the court sets a hearing, often several weeks to a few months out depending on the county. An uncontested change or an HFS agency review can be faster. Because a change reaches only installments due after notice of your filing, filing promptly protects you (750 ILCS 5/510).
If the Department of Healthcare and Family Services handles your case, you can ask its Division of Child Support Services for a free modification review. It can seek a change when the order and the guideline differ by at least 20 percent, but no less than 10 dollars a month, after 36 months (750 ILCS 5/510).
You can ask the court whenever a substantial change in circumstances occurs (750 ILCS 5/510). If the Department of Healthcare and Family Services handles your case, you can generally request a review about every three years even without a change, under federal rules. There is no limit on filing when circumstances genuinely change.
A modification changes support only for installments coming due after the other parent has due notice of your filing (750 ILCS 5/510). Support that already came due, called arrears, generally cannot be reduced or erased by a modification. Keep paying your current order to avoid building arrears while your request is pending.
Filing a motion to modify in the circuit court carries a filing fee, but you can ask the court to waive it with a fee waiver application if you cannot afford it. A modification review through the Department of Healthcare and Family Services does not charge you a fee.
Illinois has no dedicated statewide form just for modifying child support. You file a motion to modify in the circuit court that entered your order, using the approved motion forms and instructions on the Illinois Courts website, and attach current income proof for both parents (750 ILCS 5/505).
Other Illinois guides
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