Illinois Marriage Laws for Divorce: Property, Support, Parenting

Illinois divorce laws allow only one legal ground for ending a marriage: irreconcilable differences. At least one spouse must have lived in Illinois for 90 consecutive days before filing, the couple must live separate and apart for at least six months before a judge finalizes the case, and the court then divides marital property equitably, sets spousal maintenance by a statutory formula tied to net income, and allocates parenting responsibilities based on the child’s best interests.¹

Who Can File and on What Grounds

Illinois eliminated all fault-based grounds — adultery, mental cruelty, and the rest — effective January 1, 2016, through Public Act 99-90. The only ground now is that irreconcilable differences have caused the marriage to break down beyond repair and that reconciliation has either failed or would not be realistic.¹

At least one spouse must have been a resident of Illinois, or stationed here as a member of the armed services, for at least 90 consecutive days before the case can proceed in an Illinois court.²

The statute also requires the couple to live “separate and apart” for a continuous period of at least six months before the court enters a dissolution judgment. Once that six months has passed, the law creates an irrebuttable presumption that irreconcilable differences exist, so neither spouse has to prove anything further about why the marriage failed.¹ “Separate and apart” does not necessarily mean living in different homes. It refers to the end of the marital relationship, even if the spouses still share a residence for financial or practical reasons.

How a Divorce Case Moves Through Court

A divorce begins when one spouse files a Petition for Dissolution of Marriage with the circuit court clerk. The petition must be formally delivered to the other spouse through service of process. If the other spouse agrees to the divorce, they can file an Appearance voluntarily, which eliminates the need for formal service.³

After the initial filings, the case enters discovery, where both sides exchange financial information about assets, debts, income, and expenses. Courts can issue temporary orders during this period to address urgent issues like child support, parenting time, or spousal maintenance while the case is pending. In contested cases, mediation is often used to help the parties negotiate outside the courtroom.

If mediation does not resolve every dispute, the case goes to trial and a judge decides the remaining issues. Once the judge rules, or the parties settle, the court enters a Judgment of Dissolution of Marriage that formalizes every term. Filing fees vary by county.

Dividing Property and Debts

Illinois is an equitable distribution state, which means the court divides marital property in proportions it considers fair given the circumstances. Fair does not automatically mean 50/50. The court first sets aside non-marital property — assets owned before the marriage, along with gifts and inheritances received individually — and assigns those to the spouse who owns them. Everything else acquired during the marriage is marital property and is subject to division.⁴

The statute lists twelve factors the court weighs when dividing marital property. Among the ones that carry the most weight in practice:

Each spouse’s contributions, financial and otherwise. Homemaking and support of the other spouse’s career count.
The length of the marriage. Longer marriages tend to involve more intertwined finances.
Each spouse’s economic circumstances, including income, employability, health, and future earning capacity.
Any valid prenuptial or postnuptial agreement, which can override the default rules.
Tax consequences of dividing specific assets.
Custodial arrangements. The parent with primary residence of the children may receive the family home or the right to live there for a reasonable period.

Marital misconduct plays no role in property division. The no-fault framework applies to assets just as it does to grounds.⁴

Dissipation of Marital Assets

One important exception involves dissipation, meaning one spouse’s use of marital assets for purposes unrelated to the marriage while the relationship is breaking down. Gambling losses, spending on an affair, and hiding money all fit. To raise a dissipation claim, you must file a written notice of intent at least 60 days before trial, or 30 days after discovery closes, identifying the property dissipated and the time period involved. No dissipation claim can reach back more than five years before the divorce petition was filed.⁵

When dissipation is proven, the court can charge the wasted amount against the dissipating spouse’s share of the marital estate. Missing the notice deadlines forfeits the claim entirely, no matter how egregious the spending was.

Spousal Maintenance

Spousal maintenance — what most people call alimony — is not automatic. The court first decides whether an award is appropriate at all, weighing each spouse’s income and property, their realistic earning capacity, whether one spouse sacrificed career opportunities for the marriage, the standard of living during the marriage, and its duration.⁶

The Statutory Formula

For marriages lasting fewer than 20 years where maintenance is warranted, Illinois applies a specific formula. The annual maintenance amount equals 33⅓% of the payor’s net income minus 25% of the payee’s net income, subject to a cap: the payee’s total income (own earnings plus the maintenance payment) cannot exceed 40% of the couple’s combined net income.⁴

Duration follows a sliding scale. The court multiplies the length of the marriage by a factor that increases with each year, from 0.20 for marriages under five years to 0.80 for marriages between 19 and 20 years. A 10-year marriage produces roughly 4.4 years of maintenance (10 × 0.44).⁶

Long Marriages

For marriages of 20 years or more, the court has discretion to order maintenance for a period equal to the full length of the marriage, or for an indefinite term. The court can also deviate from the formula in either direction when the circumstances justify it.⁶

Parenting Time and Decision-Making

Illinois no longer uses the term “custody.” The law now refers to the “allocation of parental responsibilities,” which covers two distinct categories: significant decision-making authority (education, healthcare, religion, extracurricular activities) and parenting time (the schedule of when the child lives with each parent).⁷

Best Interest Factors

Every parenting decision is governed by the child’s best interests. The statute lists 17 factors the court considers when allocating parenting time. The ones that come up most often include:

Each parent’s wishes, and the child’s own preferences given their maturity
How much time each parent spent as a primary caretaker during the 24 months before the case was filed
The child’s adjustment to home, school, and community
Each parent’s willingness to encourage a close relationship between the child and the other parent
Any history of domestic violence or abuse
The distance between the parents’ homes and the practical logistics of transportation

Courts presume both parents are fit unless evidence shows otherwise. A judge will not restrict parenting time unless a parent’s contact would seriously endanger the child’s physical, mental, or emotional health.⁷

Parenting Plans

Both parents must file a proposed parenting plan, either jointly or separately, within 120 days after service of the petition. The plan must include a schedule designating where the child lives on specific days, how significant decisions will be made, and a mediation provision for future disputes. When parents cannot agree, the court holds an evidentiary hearing and decides based on the best interest factors.⁷

Child Support

Illinois uses the income shares model. The state estimates how much both parents would have spent on the child if the household had stayed together, then divides that obligation based on each parent’s share of their combined net income.⁸

The calculation runs in three steps. First, determine each parent’s net income by starting with gross income from all sources (wages, investments, self-employment) and subtracting taxes and certain adjustments. Second, combine the net incomes and look up the basic support obligation on a statutory schedule based on the total and the number of children. Third, divide the obligation proportionally, so each parent’s share matches their percentage of combined income. The parent with less parenting time typically pays their share to the other parent.⁹

When each parent has the child for 146 or more overnights per year, the basic support obligation is multiplied by 1.5 and then offset between the parents based on their respective incomes and time shares. The parent owing more pays the net difference. When multiple children are involved and each parent has primary care of at least one child, a separate split-care calculation applies. Courts can adjust support for extraordinary expenses like medical needs, educational costs, or childcare.⁹

Tax and Retirement Consequences

Divorce triggers federal rules that catch people off guard. The three biggest are maintenance, property transfers, and retirement accounts.

Maintenance Payments

For any divorce finalized after December 31, 2018, the Tax Cuts and Jobs Act eliminated the federal deduction for the spouse paying maintenance and removed the requirement that the receiving spouse report the payments as income. The payor pays taxes on the full amount before sending it; the payee receives it tax-free. Because the Illinois maintenance formula uses net income, it already reflects this treatment, but both sides should still factor the tax impact into settlement discussions.¹⁰

Property Transfers Between Spouses

Under federal law, transferring property between spouses as part of a divorce triggers no taxable gain or loss. The receiving spouse takes over the transferor’s original cost basis. A transfer counts as “incident to divorce” if it happens within one year after the marriage ends or is otherwise related to the divorce.¹¹

The catch is that inherited basis. If your spouse bought stock for $20,000 and it is now worth $200,000, you receive it tax-free in the divorce, but when you eventually sell you owe capital gains tax on the $180,000 gain. Current market value and tax basis can be very different numbers, and ignoring the difference during property division is one of the most expensive mistakes people make.

Selling the Family Home

Federal law allows you to exclude up to $250,000 in capital gains ($500,000 for married couples filing jointly) when selling a principal residence, provided you owned and used it as your primary home for at least two of the five years before the sale. Divorce adds two useful rules. If you received the home from your spouse as part of the divorce, your ownership period includes the time your ex owned it. And if your ex continues living in the home under a divorce decree while you retain ownership, you are treated as using it as your principal residence during that time.¹²

Dividing Retirement Accounts

Retirement accounts are often among the largest marital assets. For employer-sponsored plans like 401(k)s and pensions, the court must issue a Qualified Domestic Relations Order (QDRO), a court order that directs the plan administrator to pay a portion of the participant’s benefits to the other spouse. The order must include both spouses’ names and addresses, the plan name, and the amount or percentage being transferred. A QDRO cannot award benefits the plan does not offer.¹³

QDROs do not apply to IRAs. Dividing an IRA incident to divorce is handled through a direct transfer between accounts, which avoids early withdrawal penalties as long as the transfer is properly documented in the divorce decree. Getting a QDRO wrong, or forgetting to file one entirely, is common and can cost tens of thousands of dollars. The order should be drafted and submitted to the plan administrator for pre-approval before the divorce is finalized, not after.

Modifying Orders After the Divorce

Life changes after divorce, and Illinois law provides a mechanism for updating maintenance and child support when circumstances shift substantially.

A maintenance order can be changed or terminated only upon a showing of a substantial change in circumstances, such as a major income change, serious illness, or the recipient moving in with a new partner. The standard is intentionally high; routine fluctuations in income do not qualify. If the original order anticipated a specific future event, that event generally cannot be used as grounds for modification unless the parties agreed otherwise.¹⁴

Child support can be modified either by showing a substantial change in circumstances or, in certain cases, by demonstrating that the current order differs from the guideline amount by at least 20% and at least $10 per month. That second path applies only when a party is receiving enforcement services from the Illinois Department of Healthcare and Family Services and at least 36 months have passed since the order was entered or last modified. Support can also be adjusted to address a child’s health insurance needs.¹⁴

Either type of modification takes effect only when the court enters a new order. Unilaterally reducing or stopping payments because your situation changed, without going back to court, exposes you to contempt proceedings and accumulated arrears that the court will not forgive retroactively.

1
Justia. Illinois Code 750 ILCS 5 Part IV – Dissolution and Legal Separation
2
Illinois General Assembly. Illinois Code 750 ILCS 5/401
3
19th Judicial Circuit Court. Dissolution of Marriage/Divorce
4
Justia. Illinois Code 750 ILCS 5 Part V – Property, Support and Attorney Fees
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Illinois General Assembly. Illinois Code 750 ILCS 5/503 – Disposition of Property and Debts
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Illinois General Assembly. Illinois Compiled Statutes 750 ILCS 5/504 – Maintenance
7
Justia. Illinois Code 750 ILCS 5 Part VI – Allocation of Parental Responsibilities
8
Illinois Department of Healthcare and Family Services. About Illinois Child Support Income Shares Guidelines
9
Illinois General Assembly. Illinois Code 750 ILCS 5/505
10
Internal Revenue Service. Divorce or Separation May Have an Effect on Taxes
11
Office of the Law Revision Counsel. 26 USC 1041 – Transfers of Property Between Spouses or Incident to Divorce
12
Office of the Law Revision Counsel. 26 USC 121 – Exclusion of Gain From Sale of Principal Residence
13
Internal Revenue Service. Retirement Topics – QDRO: Qualified Domestic Relations Order
14
FindLaw. Illinois Code 750 ILCS 5/510