A prenuptial agreement, often called a prenup, is a contract two people sign before they marry. It sets the rules for how property, debt, and financial support will be handled if the marriage ends in divorce or death.
Not legal advice. This article is general information only. Prenup laws differ by state and change over time. Consult a licensed attorney in your state before acting on anything here.
In Illinois, prenups are governed by a specific state law. That law decides what your agreement can cover, how it must be signed, and when a court will refuse to enforce it.
This guide explains how Illinois treats prenuptial agreements and what couples should know before signing one.
Do Prenuptial Agreements Hold Up in Illinois?
Yes. Illinois adopted the Illinois Uniform Premarital Agreement Act, found at 750 ILCS 10. The Act applies to any premarital agreement signed on or after January 1, 1990.
Under the Act, a properly signed prenup is presumed valid. The spouse who wants to escape the agreement has to prove that one of the legal exceptions applies.
The Two Ways a Prenup Can Fail
Section 7 of the Act (750 ILCS 10/7) sets a two-part test. A prenup is not enforceable if the person challenging it proves either point below.
First, that the person did not sign the agreement voluntarily. Second, that the agreement was unconscionable when it was signed.
The second path has extra conditions. Even if the agreement was unconscionable, it can still be enforced unless the challenging spouse also shows all three of these facts: they were not given fair and reasonable disclosure of the other party’s property and debts, they did not voluntarily and in writing waive their right to that disclosure, and they did not have and could not reasonably have had adequate knowledge of the other party’s finances.
Who Carries the Burden of Proof
The spouse trying to throw out the prenup carries the burden. The person who wants to enforce the agreement does not have to prove it was fair.
This makes Illinois prenups hard to overturn when they are drafted and signed correctly. Vague claims that the deal feels one-sided are usually not enough.
What an Illinois Prenup Can Cover
Section 4 of the Act (750 ILCS 10/4) lists the subjects parties may put in a prenup. The table below summarizes the main ones.
| Topic | What you can address |
|---|---|
| Property rights | Each spouse’s rights in any property owned by either or both, now or in the future. |
| Managing property | The right to buy, sell, use, transfer, exchange, lease, or assign property during the marriage. |
| Divorce and death | How property is divided on separation, divorce, or death. |
| Spousal support | Modification or elimination of spousal maintenance, within legal limits. |
| Estate documents | Making wills, trusts, or other documents to carry out the agreement. |
| Life insurance | Ownership and disposition of a life insurance death benefit. |
| Choice of law | Which state’s law governs how the agreement is read. |
| Other terms | Any other matter, including personal rights, that does not violate public policy. |
What an Illinois Prenup Cannot Do
The Act sets clear limits. Some terms are off the table no matter what both people agree to.
- It cannot adversely affect a child’s right to support. Under 750 ILCS 10/4, child support belongs to the child, and a prenup cannot reduce or waive it.
- It cannot decide child custody or parenting time. Those decisions follow the child’s best interest at the time of divorce.
- It cannot include terms that violate public policy.
- It cannot force terms through fraud, threats, or pressure, since that defeats voluntary signing.
- It cannot fully waive maintenance if the waiver causes undue hardship under conditions that were not foreseeable when the agreement was signed.
How to Properly Sign an Illinois Prenup
The signing rules are short but strict. Missing them can make the whole agreement void.
Writing and Signatures
Section 3 of the Act (750 ILCS 10/3) requires the agreement to be in writing and signed by both parties. An oral prenup has no effect in Illinois.
The Act also states that a prenup is enforceable without consideration. That means neither person has to give the other something of value to make the contract binding, which is different from most ordinary contracts.
Notarization and Timing
Illinois law does not require a prenup to be notarized or witnessed to be valid. Many couples still notarize it to confirm identity and reduce later disputes about signatures.
Timing matters for the voluntariness test. Signing well before the wedding, rather than days before the ceremony, helps show the agreement was not signed under pressure.
Spousal Maintenance in an Illinois Prenup
Couples can modify or eliminate spousal maintenance in a prenup under 750 ILCS 10/4. This is one of the most common reasons people sign one.
There is a limit. Under 750 ILCS 10/7, if a maintenance waiver causes one spouse undue hardship because of circumstances that were not reasonably foreseeable when the agreement was signed, a court may order support despite the waiver.
A court will order only the amount of support needed to relieve that hardship. A waiver that simply leads to a tough financial outcome, without unforeseen hardship, generally still stands.
Why Financial Disclosure Matters in Illinois
Disclosure is central to the enforcement test. Before signing, each person should give the other a fair and reasonable account of their property, income, and debts.
Good practice is to attach a written list of assets and liabilities to the agreement. This makes it much harder for a spouse to later claim they were kept in the dark.
A spouse may waive the right to full disclosure, but the waiver must be voluntary and in writing. Without disclosure or a valid written waiver, an unconscionable agreement can be set aside.
What Happens Without a Prenup in Illinois
Illinois is an equitable distribution state, not a community property state. Property is not split exactly in half by default.
Under 750 ILCS 5/503, a court divides marital property in just proportions based on factors such as the length of the marriage, each spouse’s economic circumstances, and contributions to the marriage. Marital property generally means assets acquired during the marriage, while assets owned before the marriage, gifts, and inheritances are usually non-marital.
A prenup lets you set your own rules instead of leaving these decisions to a judge. Without one, the court applies the statute and the result can be hard to predict.
What Makes an Illinois Prenup Fall Apart
Most invalid prenups fail for reasons that were avoidable. The list below covers the frequent problems.
- The agreement was signed under pressure or too close to the wedding, undermining voluntary signing.
- One spouse hid assets or gave incomplete financial disclosure.
- There was no written waiver of disclosure when finances were not fully shared.
- The agreement was never put in writing or was not signed by both parties.
- The terms tried to limit child support or decide custody.
- The agreement was unconscionable when signed and the disclosure conditions were not met.
How Much Does a Prenup Cost in Illinois?
Cost depends on how complex your finances are and whether each person hires a separate lawyer. The table below shows common ranges.
| Option | Typical cost |
|---|---|
| Simple agreement, attorney drafted | $1,500 to $5,000 per couple |
| Complex assets, separate attorneys | $2,000 to $7,000 per person |
| Online platform | A few hundred dollars, flat fee |
Online services such as HelloPrenup let couples build an Illinois prenup for a flat fee, which costs far less than hiring two attorneys. For straightforward situations, this is often enough, though couples with businesses or large estates may still want a lawyer to review the final document.
Steps to Getting an Illinois Prenup
The process is straightforward when you take it in order. These steps follow the requirements in 750 ILCS 10.
- Start early, well before the wedding date, to avoid claims of pressure.
- Each person lists all property, income, and debts in writing.
- Exchange those disclosures so both people have a clear financial account.
- Decide together what the agreement will cover, such as property and maintenance.
- Put the agreement in writing and have both parties sign it.
- Consider notarizing the document, even though it is not required.
- Have each person review it carefully, ideally with independent legal advice.
- Store signed copies in a safe place where both spouses can find them.
Should You Get an Illinois Prenup?
An Illinois prenup is a practical way to set financial expectations before marriage. When it follows 750 ILCS 10, with a written agreement, honest disclosure, and voluntary signing, courts treat it as binding.
The main risks come from rushing, hiding assets, or trying to control child support and custody. Avoid those problems and your agreement has a strong chance of holding up.
Whether you use an attorney or an online platform, give yourself enough time to do it right.
Sources
- Illinois Uniform Premarital Agreement Act, 750 ILCS 10 (including 750 ILCS 10/3 formalities, 750 ILCS 10/4 content and child support, 750 ILCS 10/5 effect of marriage, 750 ILCS 10/7 enforcement).
- Illinois Marriage and Dissolution of Marriage Act, 750 ILCS 5/503 (disposition of property).
- Illinois General Assembly: Illinois Uniform Premarital Agreement Act