Does Adultery Affect Divorce in Illinois? 2026 Legal Guide

Illinois is a purely no-fault divorce state, meaning adultery does not serve as grounds for divorce and generally cannot be used to punish a cheating spouse in property division or spousal maintenance awards. Under 750 ILCS 5/401, irreconcilable differences is the sole legal ground for dissolution of marriage as of January 1, 2016. However, adultery can indirectly affect your divorce outcome through dissipation of assets claims under 750 ILCS 5/503(d)(2), prenuptial or postnuptial agreement enforcement, and in limited child custody scenarios where the affair exposed children to harmful circumstances.

How Does Illinois Law Define Adultery in Divorce Cases?

Illinois law does not require courts to consider adultery when granting a divorce or dividing marital property because the state operates under a no-fault divorce system. Under 750 ILCS 5/401, the only ground for divorce is irreconcilable differences that have caused the irretrievable breakdown of the marriage, and the court makes no finding about which spouse caused the marriage to fail. The adultery divorce Illinois framework eliminates fault-based grounds entirely.

Prior to January 1, 2016, Illinois permitted fault-based divorces where adultery could be cited as grounds. The legislature eliminated these provisions through Public Act 99-90, recognizing that fault determinations often prolonged litigation, increased costs, and caused additional emotional harm to families. Today, a spouse who has been cheated on cannot use that infidelity to obtain a divorce more quickly or secure a larger share of marital assets based solely on the affair.

Under 720 ILCS 5/11-35, adultery remains technically classified as a Class A misdemeanor in Illinois criminal law, punishable by up to one year in jail and fines up to $2,500. However, criminal prosecution for adultery is extraordinarily rare. The last documented prosecution occurred in 1997, and prosecutors generally decline to pursue these cases. For practical purposes, the criminal adultery statute is considered dormant.

The Illinois Marriage and Dissolution of Marriage Act under 750 ILCS 5/503 explicitly prohibits courts from considering marital misconduct when dividing property. Section 503(d) lists 12 factors courts must consider in equitable distribution, and adultery is not among them. This statutory framework means that proving your spouse cheated, regardless of how egregious the conduct, will not directly change your property settlement.

Does Cheating Affect Property Division in Illinois?

Adultery does not directly affect property division in Illinois because the state uses equitable distribution without considering marital fault under 750 ILCS 5/503. Illinois courts divide marital property fairly (not necessarily equally) based on factors including each spouse's contribution to the acquisition of property, the marriage duration, the economic circumstances of each spouse, and the value of non-marital property. Cheating is explicitly excluded from this analysis.

However, a cheating spouse divorce can indirectly affect property division through dissipation of assets claims. Under 750 ILCS 5/503(d)(2), dissipation occurs when a spouse uses marital property for purposes unrelated to the marriage during the marriage's breakdown. If your spouse spent marital funds on an affair — purchasing gifts, paying for hotel rooms, taking trips, or supporting a paramour — you can file a dissipation claim seeking reimbursement to the marital estate.

To pursue a dissipation claim in Illinois, you must file a notice of intent to claim dissipation no later than 60 days before trial or 30 days after discovery closes, whichever is later. The notice must identify the date or period when the marriage began undergoing irretrievable breakdown and specify the property allegedly dissipated. The dissipating spouse then bears the burden of proving by clear and convincing evidence that the expenditures were legitimate.

Important time limitations apply to dissipation claims under Illinois law. Courts will not consider any dissipation that occurred more than 5 years before the petition for dissolution was filed. Additionally, dissipation claims are barred if the aggrieved spouse waited more than 3 years after learning about the dissipation to pursue the claim. These limitations prevent spouses from dredging up ancient history to relitigate old grievances.

How Does Infidelity Impact Spousal Maintenance in Illinois?

Adultery does not affect spousal maintenance awards in Illinois because the statutory formula under 750 ILCS 5/504 calculates support based on income disparity, not marital misconduct. Illinois courts award maintenance by taking 33.33% of the payor's net income minus 25% of the recipient's net income, capped so that the recipient does not receive more than 40% of the combined net income of both spouses. This formula applies when combined gross income falls below $500,000 annually.

The legislature explicitly designed the maintenance statute to exclude fault considerations. Under 750 ILCS 5/504(a), courts consider factors including each spouse's realistic present and future earning capacity, time needed to acquire education or job training, the standard of living during the marriage, the marriage duration, and each party's age, health, and employability. Nowhere does the statute authorize reduction or increase of maintenance based on adultery.

Maintenance duration in Illinois is tied directly to marriage length under the statutory guidelines. Marriages of 5 years or less result in maintenance for 20% of the marriage length. Marriages between 5 and 10 years receive 40% of the marriage length in maintenance. The percentage increases to 60% for marriages of 10 to 15 years, and 80% for marriages lasting 15 to 20 years. Marriages of 20 years or more may receive maintenance equal to the marriage length or indefinitely at court discretion.

Even when a spouse's affair caused significant emotional harm, Illinois courts cannot use that affair to deny or reduce maintenance. The cheating spouse's need for support and the other spouse's ability to pay remain the only legally relevant considerations. This approach reflects the policy judgment that financial support obligations should not function as punishment for marital misconduct.

Can Adultery Affect Child Custody in Illinois?

Adultery generally does not affect parental responsibilities allocation in Illinois because courts focus exclusively on the child's best interests under 750 ILCS 5/602.5, which does not list infidelity as a relevant factor. Illinois replaced traditional custody terminology in 2016 with allocation of parental responsibilities (decision-making authority) and parenting time (physical custody schedule). The 15 statutory best interest factors address the child's adjustment, parental capabilities, and safety concerns — not marital misconduct.

However, affair divorce settlement negotiations involving children can be impacted when the adultery itself harmed the children. If a parent exposed children to an affair partner inappropriately, conducted the relationship in the family home while children were present, or allowed the affair to interfere with parenting responsibilities, these behaviors can be relevant to the best interest analysis. The focus remains on parental conduct that directly affects children, not the adultery itself.

Under 750 ILCS 5/602.5(c), courts consider factors including: the wishes of each parent and the child; the child's adjustment to home, school, and community; the mental and physical health of all individuals involved; the distance between parental residences; the willingness of each parent to facilitate a relationship with the other parent; and any history of domestic violence or abuse. Notably, the statute specifies that courts shall not consider conduct that does not affect the parent's relationship to the child.

This statutory language means that an affair, standing alone, is legally irrelevant to parental responsibilities allocation. A parent who cheated remains equally capable of making medical, educational, and religious decisions for their children. Only when the affair involved conduct that directly impacted the children — such as introducing them to inappropriate situations or neglecting their care — can it factor into the court's analysis.

How Do Prenuptial Agreements Address Adultery in Illinois?

Prenuptial and postnuptial agreements can make adultery financially consequential in Illinois divorce cases, creating an exception to the general rule that marital fault is irrelevant. Under the Illinois Uniform Premarital Agreement Act at 750 ILCS 10, couples can contract for specific consequences if either spouse commits adultery, including forfeiture of property rights or waiver of spousal maintenance.

Infidelity clauses in marital agreements typically provide that if a spouse engages in adultery, they forfeit certain property rights, receive reduced or no spousal maintenance, or must pay the other spouse a specific sum. Illinois courts enforce these provisions if the agreement was executed voluntarily, both parties provided fair financial disclosure, and the terms are not unconscionable at the time of enforcement.

For an infidelity clause to be enforceable, the agreement must define adultery clearly. Vague provisions referencing marital misconduct may be unenforceable due to ambiguity. The agreement should specify what conduct constitutes a breach, what evidence standard applies, and what financial consequences follow. Courts interpret these provisions strictly, so precise drafting is essential.

A cheating and custody agreement cannot override Illinois law governing parental responsibilities. While prenuptial agreements can address property and support, they cannot predetermine custody arrangements or parenting time schedules. Any provisions purporting to award custody to one parent if the other commits adultery are unenforceable because courts must make custody determinations based on the child's best interests at the time of divorce.

What Evidence Is Required to Prove Dissipation From an Affair?

Proving dissipation from an affair requires documenting specific expenditures, demonstrating they occurred during the marriage breakdown, and showing they served no marital purpose. Under Illinois case law interpreting 750 ILCS 5/503(d)(2), the spouse alleging dissipation must establish a prima facie case by showing the other spouse had access to marital funds and explaining how those funds were used.

Common evidence used to prove affair-related dissipation includes credit card statements showing purchases for the affair partner, bank records documenting cash withdrawals or transfers, hotel and travel receipts, gift purchases, and communications confirming the affair relationship. Digital evidence such as text messages, emails, and social media posts can establish both the existence of the affair and specific expenditures related to it.

Once the alleging spouse establishes a prima facie case, the burden shifts to the dissipating spouse to prove by clear and convincing evidence that the expenditures were for a marital purpose. If the dissipating spouse cannot provide satisfactory explanation for missing funds during the period of marriage breakdown, the court may presume dissipation occurred and adjust the property division accordingly.

Illinois courts have found dissipation in affairs involving apartment rentals for paramours, luxury gifts, vacation expenses, car payments, and cash transfers. The amounts can be substantial — some published cases involve dissipation findings of $50,000 to $200,000 or more. The court may award the non-dissipating spouse additional property equal to their share of the dissipated amount, effectively requiring reimbursement from the dissipating spouse's share of the marital estate.

How Much Does Divorce Cost in Illinois?

Divorce filing fees in Illinois range from $306 in smaller counties like Stephenson County to $388 in Cook County as of March 2026. The responding spouse pays an additional appearance fee ranging from $181 to $251 depending on the county, with Cook County charging $251 for appearances. Service of process through the Sheriff's office costs approximately $60 in Cook County, though private process servers may charge more.

Illinois provides fee waivers for individuals who cannot afford court costs under Illinois Supreme Court Rule 298. You may qualify if your household income falls at or below 125% of the federal poverty guidelines. For a single-person household in 2026, this threshold is approximately $18,500 in annual income. To request a waiver, submit an Application for Waiver of Court Fees with documentation of your financial circumstances.

Beyond filing fees, contested divorces involving adultery-related issues typically cost significantly more due to additional discovery, expert witnesses, and trial time. Dissipation claims require extensive forensic accounting to trace marital funds, which can cost $5,000 to $20,000 or more depending on the complexity of the financial picture. Attorney fees for contested Illinois divorces range from $15,000 to $75,000 or higher for complex cases involving substantial assets and contentious disputes.

Illinois Divorce Residency and Procedural Requirements

At least one spouse must have maintained continuous Illinois residency for a minimum of 90 days before filing a Petition for Dissolution of Marriage under 750 ILCS 5/401(a). Illinois does not impose a pre-filing waiting period, meaning you can file immediately upon meeting the residency requirement. The 90-day period must be satisfied by the date of judgment, so technically you could file before the 90 days expire if you will meet the requirement before finalization.

Illinois has no mandatory waiting period between filing and finalization for standard divorces. However, joint simplified dissolution requires that the parties have been separated for at least six months. The joint simplified procedure under 750 ILCS 5/451 is available only when: the parties have no children together; no adoptions occurred during the marriage; the wife is not pregnant; neither party owns real estate; marital property is valued at less than $50,000; and combined gross income does not exceed $60,000.

For contested divorces involving dissipation claims related to adultery, the process typically takes 12 to 24 months from filing to finalization. Discovery regarding alleged dissipation can be extensive, requiring production of years of financial records, depositions of the parties and potentially the affair partner, and expert forensic accounting testimony. Trial on dissipation issues may require one to three days of court time depending on the complexity and dollar amounts involved.

Frequently Asked Questions About Adultery and Divorce in Illinois

Can I get a larger share of property because my spouse cheated?

No, Illinois law does not permit courts to award a larger property share based solely on adultery. Under 750 ILCS 5/503, marital misconduct including infidelity is not a factor in equitable distribution. However, if your spouse spent marital funds on the affair, you can file a dissipation claim seeking reimbursement of your share of those expenditures. Dissipation awards effectively increase your property share by compensating for wasted marital assets.

Will my spouse's affair affect our children's custody arrangement?

Adultery alone does not affect parental responsibilities allocation under Illinois law. Courts determine custody based on the child's best interests under 750 ILCS 5/602.5, which does not list infidelity as a relevant factor. Only if the affair directly harmed the children — through inappropriate exposure, neglect, or similar conduct — can it impact custody. The affair itself, without evidence of harm to children, is legally irrelevant.

Is adultery a crime in Illinois?

Yes, adultery remains a Class A misdemeanor under 720 ILCS 5/11-35, punishable by up to one year in jail and $2,500 in fines. However, criminal prosecution is extraordinarily rare — the last documented case occurred in 1997. For practical purposes, the statute is not enforced. Your spouse's affair will not result in criminal charges, and adultery's technical illegality has no impact on divorce proceedings.

How long do I have to file a dissipation claim for affair expenses?

Illinois imposes two time limitations on dissipation claims. Courts will not consider dissipation occurring more than 5 years before the divorce petition was filed. Additionally, claims are barred if you wait more than 3 years after learning about the dissipation. You must also file a formal notice of intent to claim dissipation at least 60 days before trial or 30 days after discovery closes.

Can a prenuptial agreement make adultery affect my divorce?

Yes, prenuptial and postnuptial agreements can create financial consequences for adultery that would not otherwise exist under Illinois law. The Illinois Uniform Premarital Agreement Act at 750 ILCS 10 permits infidelity clauses providing for property forfeiture, maintenance reduction, or specific payments if a spouse commits adultery. These provisions are enforceable if the agreement was voluntary, included fair disclosure, and is not unconscionable.

How much can I recover in a dissipation claim for my spouse's affair?

Recovery depends on proving specific expenditures with documentation. Illinois courts have awarded dissipation judgments ranging from a few thousand dollars to over $200,000 in cases involving substantial affair-related spending. Common recoverable expenses include gifts to affair partners, travel, apartment or hotel costs, and cash transfers. You receive your equitable share (typically 50%) of proven dissipated amounts.

Does it matter if my spouse's affair partner was also married?

The marital status of the affair partner does not change the legal analysis in your Illinois divorce. Whether the paramour was single or married has no impact on property division, maintenance, or custody determinations. Dissipation claims focus solely on marital funds your spouse spent on the affair, regardless of the other person's marital status. The affair partner cannot be sued for alienation of affection in Illinois.

Can I use evidence of the affair obtained by hacking my spouse's phone?

Evidence obtained illegally may be inadmissible and could expose you to civil or criminal liability. Illinois law prohibits unauthorized access to electronic communications under the Illinois Eavesdropping Act. However, evidence legally obtained — such as credit card statements, bank records, and communications discovered through proper divorce discovery — is admissible to prove dissipation. Consult an attorney before gathering evidence.

Will my spouse have to pay my attorney fees if they cheated?

Illinois does not award attorney fees as punishment for adultery. Under 750 ILCS 5/508, courts may order fee contributions when one spouse lacks sufficient resources to pay and the other has the ability to contribute. The cheating itself is irrelevant — only the parties' relative financial circumstances determine fee allocation. However, if your spouse's litigation misconduct increases costs unnecessarily, sanctions may be available.

How do I prove my spouse spent marital money on an affair?

Start by gathering financial records including bank statements, credit card bills, and tax returns. Look for unexplained withdrawals, unfamiliar purchases, travel expenses, jewelry, clothing, or gifts inconsistent with your spouse's normal spending. Subpoenas through divorce discovery can obtain records your spouse controls. A forensic accountant can trace funds and quantify dissipation. Text messages or emails referencing gifts or expenses can corroborate financial evidence.