A divorce judgment is final on the day it’s entered, but the orders within it — parenting time, child support, allocation of parental responsibilities, maintenance — can be modified when circumstances change. The Illinois Marriage and Dissolution of Marriage Act sets out the standard, and the standard is more demanding than most people expect.
The general rule: substantial change
Most modifications require a substantial change in circumstances since the entry of the prior order. The change must be significant enough that the original order no longer serves its purpose, and it must have happened after the order was entered. Changes the court already knew about (and accounted for) typically don’t qualify.
Modifying child support
Under section 510 of the IMDMA, child support may be modified when:
- There has been a substantial change in circumstances (e.g., income change, employment change, change in parenting schedule, change in child’s needs).
- Where the inconsistency between the statutory guideline amount and the existing order is at least 20% or $10/month (whichever is greater) — even without proving a substantial change.
- Every three years on request by either party, the court reviews the order against current circumstances.
Common income changes that trigger modification:
- Job loss — but voluntary unemployment or underemployment leads the court to impute income at the prior level.
- Significant promotion or new job.
- Retirement — depends on age, health, and good faith. Early retirement to avoid support is generally not protected.
- Self-employment income fluctuation — but courts look at multi-year averages.
- A new child from a new relationship — relevant but not automatically determinative.
Modifying maintenance
Section 510(a-5) applies the same substantial-change standard to maintenance. Specifically enumerated factors include:
- Changes in either party’s employment status, earning capacity, or income.
- Impairment of either party’s earning capacity.
- Tax consequences of maintenance.
- Property owned by each party that produces income.
- Increased or reduced needs of either party.
- Cohabitation — terminates maintenance entirely if the recipient cohabits with another adult on a continuing conjugal basis (section 510(c)).
- Remarriage — terminates maintenance entirely.
Modifying parenting time and decision-making
Section 610.5 governs modifications to the allocation of parental responsibilities and parenting time. The standard depends on what you’re trying to modify and when:
- Within 2 years of the original allocation, modification of decision-making requires evidence that the child’s present environment may endanger seriously their physical, mental, moral, or emotional health. A very high bar.
- After 2 years, the standard is a substantial change in circumstances that supports modification being in the child’s best interest.
- Minor schedule changes — short visits, holiday adjustments — can typically be modified by agreement at any time, or by court order on a lesser showing.
- Relocation by a parent — governed by its own statute (section 609.2) with specific notice requirements and a distinct analysis.
Document the change. Modification petitions live or die on the documentation of the changed circumstances. Pay stubs, tax returns, school records, medical records, written communications between parents — the case you build at the petition stage is the case the court decides.
What gets modified, what gets enforced
Not every problem with a decree is a modification problem. Some are enforcement problems. The distinction matters:
- Modification — "the order should change going forward."
- Enforcement — "the other party isn’t following the existing order; please make them."
Enforcement is typically pursued through a petition for rule to show cause alleging contempt of court. Remedies range from order clarification through monetary sanctions to (in rare cases) incarceration.
Process and timeline
- Petition for modification is filed in the same case as the original judgment.
- Served on the other party, who has 30 days to respond.
- Discovery — financial affidavits, income documentation, sometimes depositions.
- Temporary relief may be available pending a hearing.
- Hearing or trial if not resolved by agreement.
- New order entered — which can itself be modified later if circumstances change again.
Most modifications resolve by agreement before reaching trial. The cases that don’t typically involve income disputes (especially with self-employed parties) or significant parenting changes.
If your post-decree situation has changed materially, the conversation with counsel is worth having before the situation gets entrenched. Earlier petitions are easier to litigate than ones where months of non-compliance have already accumulated.
