Four Reasons Your Prenuptial Agreement Might Be Unenforceable

 Posted on October 14, 2026 in Family Law

A prenuptial agreement helps couples decide how financial matters will be handled if their marriage ends. When divorce becomes a possibility, you might question whether the agreement you signed years ago will hold up in court.

Illinois courts enforce valid prenups, but problems with how an agreement was prepared or signed can support a challenge. Certain spousal support provisions also deserve review when unexpected circumstances create serious hardship. If you have concerns about your prenuptial agreement in 2026, our Kane County, IL family law attorneys will explain your options.

What Are Four Reasons to Challenge a Prenuptial Agreement in Illinois?

Illinois law provides several grounds to challenge a prenup or a specific term within it. Four reasons to seek a review are:

• You were forced or pressured into signing rather than signing freely.
• The terms were extremely unfair when signed, and the required financial disclosures were not made.
• An unexpected hardship makes a spousal support waiver too harsh to enforce.
• The agreement was not put in writing and signed by both spouses.

Each reason has its own legal requirements. Some affect the whole agreement, while others affect only a support provision. Simply regretting the agreement does not give you grounds to set it aside.

Can You Challenge a Prenup if You Were Pressured to Sign?

Under 750 ILCS 10/7, a prenup is unenforceable if the spouse challenging it proves they did not sign voluntarily. The judge looks at what happened before and during the signing.

Threats and efforts to keep you from reading the terms could support a challenge. Messages showing that you asked for more time or were denied a chance to review the document also help explain what happened.

Getting a prenup shortly before the wedding does not automatically make it invalid. The court considers whether the timing, along with other undue pressure, kept you from making a free choice.

Can Unfair Terms or Hidden Assets Make an Illinois Prenup Invalid?

Unfair terms alone do not make a prenup invalid. To succeed on this ground, you must show that the agreement was unconscionable when signed. This means the terms were so unfair that they meet the law’s standard for refusing enforcement.

You must also prove that you did not receive fair financial disclosure, did not voluntarily waive further disclosure in writing, and did not have enough knowledge of your spouse’s finances or a reasonable way to gain it.

For example, an undisclosed business could raise concerns about what you knew before signing. The judge would review the business records, any financial information you received, and any waiver you signed. A missing asset does not, by itself, prove every part of this challenge.

How Can an Unexpected Hardship Affect a Spousal Support Waiver in Illinois?

A court can order spousal maintenance despite a prenup that limits or bars it. This exception applies when enforcing the waiver would cause undue hardship because of events that were not reasonably foreseeable when you signed. A serious illness that leaves a spouse unable to work could raise this issue.

The judge reviews the hardship and whether the spouses could reasonably have expected those circumstances when signing. The court is allowed to order enough support to avoid the hardship. This does not automatically cancel the agreement’s property terms.

Is an Unsigned or Verbal Prenuptial Agreement Enforceable in Illinois?

According to 750 ILCS 10/3, a prenup must be in writing and signed by both spouses. A spoken promise about keeping separate property or giving up support does not meet those requirements.

An unsigned draft is not enough either. If you exchanged several versions, check which one both of you signed and whether its attachments are included. Before assuming the agreement lacks a signature, check for a complete copy. Your spouse or the lawyers who prepared it might have the signed version.

Does Signing an Illinois Prenup Without Your Own Lawyer Make It Invalid?

Not having your own lawyer does not, by itself, make an Illinois prenup invalid. The court looks at whether you signed freely and whether other grounds exist to challenge the agreement.

If your spouse’s lawyer prepared the prenup, that lawyer represented your spouse. Being denied time to seek your own legal advice could help support a claim that you were pressured into signing. Choosing to sign without a lawyer, despite having time to consult one, is a different situation.

A challenge should explain what prevented you from making a free and informed choice. The lack of separate lawyers alone is not enough to set the agreement aside.

Contact a St. Charles, IL Prenuptial Agreement Lawyer

Questions about a prenup can affect your financial decisions throughout a divorce. At Mirabella, Kincaid, Frederick & Mirabella, LLC, our attorneys will review the agreement and explain your options for seeking enforcement or challenging its terms.

MKFM Law serves family law clients from our offices located in Kane, DuPage, and DeKalb Counties. Contact our Kane County, IL family law attorneys or call 630-665-7300 to schedule an initial attorney meeting.