Illinois Marriage Laws: Requirements, Divorce, and Annulment

Illinois marriage laws set who can marry, how to get licensed, what rights and duties the marriage creates, and how a marriage ends. The controlling statute is the Illinois Marriage and Dissolution of Marriage Act (750 ILCS 5/), which covers everything from the age to marry through the division of property in divorce. The state does not recognize new common law marriages, uses a no-fault-only system for divorce, and applies a formula for spousal maintenance in most cases.

Who Can Legally Marry

Both parties must be at least 18 to marry without restriction. A 16- or 17-year-old may marry with written consent from both parents or a legal guardian, or with a judge’s approval. If one parent cannot be located after a real effort to find them, the other parent can sign an affidavit describing the search and consent alone.¹

Both people must enter the marriage voluntarily. A marriage produced by force or coercion can be set aside by a court.

Illinois prohibits several categories of marriage outright:

A person who is already in an undissolved marriage, civil union, or similar legal relationship cannot marry.
Parents cannot marry their children.
Siblings cannot marry each other, including half-siblings and adoptive siblings.
Aunts or uncles cannot marry nieces or nephews.
First cousins cannot marry, with two narrow exceptions: both parties are 50 or older, or one party can show proof of permanent infertility.²

Getting a License and Holding the Ceremony

Both people must appear together at a county clerk’s office, complete an application, and pay the license fee. Fees vary by county; Cook County charges $60.³ Some counties offer a discount for couples who complete a premarital education course. Illinois does not require a blood test.

The license takes effect one day after it is issued, so the ceremony cannot happen on the same day the license is picked up unless a court orders otherwise. Once effective, the license is valid for 60 days. Miss that window and a new license is required.⁴

The list of officiants is broad. It includes any judge or retired judge of a court of record, a judge of the Court of Claims, the county clerk in counties with two million or more residents (essentially Cook County), any mayor or village president currently in office, and any officiant in good standing with a religious denomination, Indian Nation, Tribe, or Native Group.⁵ Online-ordained ministers sit in a gray area in Illinois; couples who want certainty often use a judge or a clearly credentialed religious officiant.

What Marriage Changes Legally

Property and Debts

Illinois divides everything a couple owns into two categories. Marital property covers virtually everything either spouse earns or acquires during the marriage. Non-marital property covers assets owned before the marriage, gifts or inheritances received by one spouse, and anything excluded by a valid prenuptial or postnuptial agreement.⁶ Growth in the value of non-marital property generally stays non-marital, but the marital estate may be entitled to reimbursement when marital funds or effort contributed to that growth.

Marriage does not automatically make you liable for your spouse’s individual debts. If your name is not on a credit account, that debt generally belongs to your spouse alone. Under federal credit-reporting rules, though, creditors must report account activity in both spouses’ names when both are contractually liable or when one is an authorized user, and a spouse can also ask that an existing account be reported in both names.⁷ Co-signing or sharing accounts merges credit histories in ways that outlive the marriage.

Children

Both parents share the obligation to support their children financially. Decisions about a child’s education, health care, and welfare are typically made jointly unless a court orders otherwise. Illinois applies a “best interests of the child” standard for all custody-related questions, which the state now calls “allocation of parental responsibilities.”

Federal Benefits

Marriage also unlocks benefits Illinois law alone cannot provide. A spouse can collect Social Security retirement benefits based on the other spouse’s earnings record, up to 50% of the worker’s primary insurance amount at full retirement age. Claiming at 62 reduces the benefit to as little as 32.5%.⁸ Survivor benefits are available when the higher-earning spouse dies, provided the marriage lasted at least nine months before the death, with exceptions for accidental or line-of-duty deaths.⁹

A spouse who has not worked enough to qualify for Medicare Part A on their own record can qualify based on their partner’s work history and receive premium-free coverage.¹⁰

For federal taxes in 2026, married couples filing jointly get a $32,200 standard deduction, exactly double the $16,100 single-filer deduction, and wider brackets at the lower and middle ranges. The exception is at the top: the 37% rate hits at $768,700 for joint filers, well below double the $640,600 single-filer threshold, so two high earners can pay more married than single.¹¹

Declaring a Marriage Invalid

Illinois uses “declaration of invalidity” for what most people call annulment. The grounds are narrow and different from the grounds for divorce:

One party could not consent because of mental illness, intoxication, or the influence of drugs at the ceremony.
One party was coerced or deceived, with the fraud going to something essential about the relationship rather than a peripheral issue.
One party was physically unable to consummate the marriage and the other did not know at the time of the ceremony.
A party was 16 or 17 and married without the required parental or judicial consent.
The marriage falls into a prohibited category, such as bigamy or a close family relationship.¹²

Prohibited and bigamous marriages are void from the start and have no legal effect. The other categories are voidable, meaning the marriage stays recognized until a court declares it invalid. Time limits apply to several grounds, so this option does not stay open indefinitely.

Ending a Marriage in Illinois

Illinois allows only one ground for divorce: irreconcilable differences that have caused an irretrievable breakdown of the marriage. Fault grounds like adultery and cruelty were eliminated years ago. At least one spouse must have been an Illinois resident, or stationed in Illinois as a member of the military, for at least 90 days before filing.¹³

Living separate and apart for at least six continuous months before the judgment is entered counts as conclusive proof that irreconcilable differences exist. Courts have recognized that spouses can live separate and apart under the same roof if they have genuinely disengaged from the marital relationship. The six months is not a waiting period before filing. It is a shortcut: after that time passes, neither spouse needs to argue that the marriage has broken down.¹³

Filing and Responding

The process starts when one spouse files a Petition for Dissolution of Marriage in the circuit court of the county where either spouse lives. Filing fees vary by county and typically run a few hundred dollars, with waivers available for people who qualify on income. The petitioner then serves the other spouse with a summons. The responding spouse has 30 days to file an entry of appearance and, if they choose, an answer addressing the petition’s terms.¹⁴

Uncontested cases, where the spouses agree on property, support, and parenting, tend to move quickly. Contested cases can be sent to mediation before any trial on custody or finances.

Dividing Property

Illinois divides marital property equitably, meaning fairly based on the circumstances rather than automatically 50/50. The court weighs each spouse’s contribution to acquiring the property, the length of the marriage, each spouse’s economic situation, any prenuptial agreement, and the tax consequences of the proposed division.⁶ Non-marital property stays with its owner.

Retirement accounts and pensions earned during the marriage are marital property. Dividing a private employer-sponsored plan requires a Qualified Domestic Relations Order, or QDRO. This is a separate court order that tells the plan administrator to pay a portion of the benefits to the non-employee spouse. The order must identify both parties, specify the amount or percentage, and name the plan, and it cannot award more than the plan provides or a type of benefit the plan does not offer.¹⁵ A QDRO that fails federal requirements will be rejected by the plan administrator, and fixing it later is expensive.

Spousal Maintenance

Illinois uses a formula for spousal maintenance when the couple’s combined gross income is under $500,000 and the payor has no prior support obligation from another case. The guideline amount is 33⅓% of the payor’s net annual income minus 25% of the payee’s net annual income, and the payment cannot raise the payee’s total income above 40% of the couple’s combined net income.¹⁶

Duration depends on the length of the marriage. The court multiplies that length by a factor that grows with each year: a five-year marriage uses 0.24 (about 1.2 years of maintenance), and a 15-year marriage uses 0.64 (about 9.6 years). For marriages of 20 years or longer, the court can order maintenance for a period equal to the marriage or indefinitely.¹⁶ Courts can deviate when circumstances justify it, but the formula is the starting point.

Health Coverage After Divorce

A spouse covered under the other spouse’s employer-sponsored plan loses that coverage when the divorce is finalized. Federal law gives the former spouse the right to continue coverage through COBRA for up to 36 months. The covered employee or the former spouse must notify the plan administrator within 60 days of the divorce, and the former spouse then has another 60 days to elect coverage.¹⁷ Premiums run the full cost of coverage plus a 2% administrative fee, which is a jump for spouses used to employer-subsidized rates. Missing the 60-day notification window means losing COBRA entirely.

Same-Sex Marriage

Illinois legalized same-sex marriage through the Religious Freedom and Marriage Fairness Act, signed in November 2013 and effective June 1, 2014. Same-sex couples have the same rights and obligations as opposite-sex couples across every part of Illinois marriage law.¹⁸ The U.S. Supreme Court’s 2015 decision in Obergefell v. Hodges then recognized a constitutional right to same-sex marriage nationwide.¹⁹ The federal Respect for Marriage Act, enacted in 2022, requires every state to give full faith and credit to marriages valid where performed regardless of the sex, race, ethnicity, or national origin of the spouses.²⁰

Common Law Marriage

Illinois does not recognize common law marriages formed within the state, and has not since 1905. Living together, sharing finances, or calling each other spouses does not create a legally recognized marriage without a license and ceremony.²¹

A couple who established a valid common law marriage in a state that recognizes them, such as Colorado or Texas, and then moved to Illinois is a different case. Illinois honors those out-of-state marriages under the general rule that a marriage valid where performed is valid here, as long as it does not violate state public policy.²² Once recognized, that marriage carries the same property, support, and parental-responsibility consequences as any other Illinois marriage.

1
Illinois General Assembly. Illinois Code 750 ILCS 5/203 – License to Marry
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Illinois General Assembly. Illinois Code 750 ILCS 5/212 – Prohibited Marriages
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Cook County. Marriage Licenses
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Illinois General Assembly. Illinois Code 750 ILCS 5/207 – Effective Date of License
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Illinois General Assembly. Illinois Code 750 ILCS 5/209 – Solemnization and Registration
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Illinois General Assembly. Illinois Code 750 ILCS 5/503 – Disposition of Property and Debts
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Consumer Compliance Outlook. Furnishers Obligations for Consumer Credit Information Under the CARES Act, FCRA, and ECOA
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Social Security Administration. Benefits for Spouses
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Social Security Administration. POMS GN 00305.100 – Marital Relationship Duration
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Centers for Medicare and Medicaid Services. Original Medicare Part A and B Eligibility and Enrollment
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Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
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Illinois General Assembly. Illinois Code 750 ILCS 5/301 – Declaration of Invalidity, Grounds
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Illinois General Assembly. Illinois Code 750 ILCS 5/401 – Dissolution of Marriage
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19th Judicial Circuit Court, IL. Dissolution of Marriage/Divorce
15
U.S. Department of Labor. QDROs Under ERISA – A Practical Guide to Dividing Retirement Benefits
16
Illinois General Assembly. Illinois Code 750 ILCS 5/504 – Maintenance
17
Centers for Medicare and Medicaid Services. COBRA Continuation Coverage Questions and Answers
18
Illinois State Bar Association. Same-Sex Marriage Comes to Illinois
19
Legal Information Institute. Obergefell v. Hodges
20
Office of the Law Revision Counsel. 28 USC 1738C – Certain Acts, Records, and Proceedings and the Effect Thereof
21
Illinois General Assembly. Illinois Code 750 ILCS 5/214 – Invalidity of Common Law Marriages
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Illinois General Assembly. Illinois Code 750 ILCS 5/213 – Validity