750 ILCS 5/511 is the procedural section of the Illinois Marriage and Dissolution of Marriage Act that tells you how to get back into court to enforce or modify a judgment of dissolution, legal separation, or invalidity of marriage after the case has closed. It governs where you file, how you notify the other party, and what happens when both of you have moved away from the original court. It does not tell you what you have to prove to actually win a modification. Those standards live in other sections of the Act.
What Section 511 Does and Doesn’t Cover
Section 511 is the doorway back into court. It addresses four situations: modifying or enforcing a judgment within the original circuit, transferring a case when both parties have moved, enrolling and enforcing a judgment from a different Illinois circuit, and transferring the collection of support payments to a new county’s clerk.1Illinois General Assembly. Illinois Compiled Statutes 750 ILCS 5/511 – Procedure
What it does not do is set the legal standard for changing anything. Child support and maintenance modifications are governed by Section 510. Parental responsibilities and parenting time are governed by Section 610.5. Section 511 gets you through the courthouse door; those other sections decide whether the judge grants your request.
Where to File
The default rule is simple: file your petition in the judicial circuit where your judgment was originally entered or last modified.1Illinois General Assembly. Illinois Compiled Statutes 750 ILCS 5/511 – Procedure
Pay attention to the word “circuit.” Illinois has 25 judicial circuits, and only seven of them cover a single county (Cook, DuPage, Kane, Lake, McHenry, St. Clair, and Will). The other 18 each span between two and twelve counties.2State of Illinois Office of the Illinois Courts. The Circuit Court of Illinois If your divorce was finalized in a multi-county circuit, you file within that circuit even if you now live in a different county inside it.
Filing Across Circuits
If you need to enforce or modify a judgment that was entered in a different Illinois judicial circuit, Section 511(b) requires you to file a petition in the new circuit, attach a copy of the original judgment, and mail notice to the clerk of the court that originally entered the judgment.1Illinois General Assembly. Illinois Compiled Statutes 750 ILCS 5/511 – Procedure Once that is done, the new circuit has full authority to handle the matter.
When Both Parties Have Moved
If neither you nor the other party still lives in the county where the judgment was entered or last modified, either of you can ask the court to transfer the case to another county or judicial circuit where one of you currently resides. The court can also order a transfer on its own.1Illinois General Assembly. Illinois Compiled Statutes 750 ILCS 5/511 – Procedure
One important restriction: when the post-judgment proceeding involves maintenance or child support, the transfer must go to the county or circuit where the person receiving (or set to receive) those payments lives. The rule protects the recipient from being dragged to a distant courthouse by the payor.
Transferring Just the Payment Collection
Section 511(d) addresses a narrower situation. When a judgment requires maintenance or child support to be paid through the clerk of the court and neither party still lives in the original county, the court can transfer the collection function to the clerk in the county where the recipient lives.1Illinois General Assembly. Illinois Compiled Statutes 750 ILCS 5/511 – Procedure This is an administrative shift of the payment processing only. The case itself does not move.
How to Notify the Other Party
Section 511(a) gives you two methods for notifying the other side that you have filed a petition: mail notice to their last known address, or have a summons issued and served.1Illinois General Assembly. Illinois Compiled Statutes 750 ILCS 5/511 – Procedure The statute does not require certified mail with a return receipt for routine post-judgment petitions, though many attorneys use certified mail as a practical matter to create a paper trail. Summons service follows the standard rules under Illinois law, which can include the county sheriff’s office or a licensed private process server.
Sheriff service carries a fee that varies by county. In Cook County, for example, the sheriff charges $60 for e-filed service and $95 for paper filings.3Cook County Sheriff’s Office. Serving Process (Summons) Whatever method you choose, the other party must receive proper notice before a judge can rule on any modification request.
What You Still Have to Prove
Getting through the procedural door is the easy part. The harder question is whether the judge will grant what you are asking for. The standard depends on what you want to change.
For child support, Section 510 lets you modify in two ways. One requires a substantial change in circumstances since the last order. The other does not require any change at all: if the existing amount differs from the current guideline amount by at least 20% (and at least $10 per month), a party receiving enforcement services from the Department of Healthcare and Family Services can seek modification based on that inconsistency, provided at least 36 months have passed since the order was entered or last modified. A modification can also be sought to address a child’s health care needs without proving a change in circumstances.4Illinois General Assembly. Illinois Compiled Statutes 750 ILCS 5/510 – Modification and Termination of Provisions for Maintenance, Support, Educational Expenses, and Property Disposition
For maintenance, Section 510 requires a substantial change in circumstances. There is no percentage-based shortcut.4Illinois General Assembly. Illinois Compiled Statutes 750 ILCS 5/510 – Modification and Termination of Provisions for Maintenance, Support, Educational Expenses, and Property Disposition
For parental responsibilities (decision-making authority), Section 610.5 generally bars a modification motion until at least two years after the current order was entered, unless you can show through affidavits that the child’s present environment may seriously endanger their physical, mental, or emotional health. Parenting time can be modified at any time on a showing of changed circumstances and the child’s best interests, with no serious-endangerment threshold. In either case, the court must find a substantial change in circumstances by a preponderance of the evidence. The court can also approve a modification without any changed-circumstances showing if it reflects how the child has actually been living for at least six months without parental objection, if it qualifies as a minor modification, or if both parents agree.5Illinois General Assembly. Illinois Compiled Statutes 750 ILCS 5/610.5 – Modification of Parenting Plan and Allocation Judgment
If a Parent Has Moved Out of State
Section 511 governs procedure inside Illinois. Once a parent moves to another state, the question of which state has power to modify a custody order is answered by the Uniform Child Custody Jurisdiction and Enforcement Act, codified at 750 ILCS 36. The core rule is that the state that issued the original order keeps exclusive jurisdiction until either no parent or child still lives there, or an Illinois court determines there is no longer a significant connection to Illinois and that substantial evidence about the child’s life is no longer available here.6Illinois General Assembly. Illinois Compiled Statutes 750 ILCS 36/202 – Exclusive, Continuing Jurisdiction You cannot simply file in your new state and expect that court to rewrite an Illinois custody order. The new state’s court must first confirm that Illinois has relinquished jurisdiction.
Filing Process and Costs
Illinois requires electronic filing for all civil cases, including family law matters, through an electronic filing service provider of your choice.7State of Illinois Office of the Illinois Courts. Information for Filers Without Lawyers The filing generates a timestamped confirmation that establishes your filing date.
Filing fees for a post-judgment modification vary by county. Some counties charge as little as $50 for a motion filed within 30 days of the judgment and $75 if filed later; others charge more. Contact the circuit clerk’s office for the exact amount. If you cannot afford the fee, you can submit an Application for Waiver of Court Fees, a standardized form that all Illinois courts must accept.8State of Illinois Office of the Illinois Courts. Fee Waiver for Civil Cases
The Illinois Supreme Court publishes standardized family law forms through the courts website.9State of Illinois Office of the Illinois Courts. Approved Statewide Standardized Forms Your petition should use the same case caption as the original proceeding and clearly identify the specific provisions of the judgment you want changed. Attaching a copy of the existing order is good practice generally and a statutory requirement when you are filing across circuits under Section 511(b).
The Existing Order Stays in Force Until a Judge Signs a New One
A common and expensive misconception: people assume that once they file, the current order stops applying. It does not. You remain bound by the existing order until a judge enters a new one. If your income drops and you stop paying ordered child support while your modification petition is pending, you are accumulating arrears that can be enforced against you.
Illinois courts do have discretion to make a child support modification retroactive to the date the petition was filed, but not earlier. Whether the judge actually makes it retroactive depends on the circumstances. That is a strong reason to file promptly when circumstances change rather than waiting months to see how things develop. The filing date sets the earliest possible effective date for any change.