What Is the Purpose of a Postnuptial Agreement?

 Posted on May 21, 2026 in Family Law

A postnuptial agreement, often called a "postnup," is a legal contract that married couples sign after the wedding to set rules about property, debt, and financial support if the marriage ends. If you missed the chance to sign a prenup before getting married, or if your financial situation has changed significantly since the wedding, a postnup can give you many of the same protections. A DuPage County, IL family law lawyer can help you decide whether a postnuptial agreement makes sense for your situation in 2026.

What Can an Illinois Postnuptial Agreement Cover?

Unlike prenups, postnups do not have a specific statute in Illinois. Instead, they are governed by general contract law principles and the Illinois Marriage and Dissolution of Marriage Act (750 ILCS 5/502). To hold up in court, a postnup must be in writing, signed voluntarily by both spouses, and supported by full financial disclosure from each party. The terms also cannot be "unconscionable." In other words, enforcement of the postnuptial agreement can’t result in leaving one spouse destitute.

Within these boundaries, a postnup can address a wide range of financial issues:

• How marital property and debt will be divided if you divorce
• Whether spousal maintenance (alimony) will be paid, and for how long
• How separately owned property, like a business or inheritance, will be classified and protected
• How assets will pass to children or other heirs upon a spouse's death

Note that postnuptial agreements cannot address issues regarding child support or parenting time. These will be determined by the court to protect the child’s best interests in the event of a divorce.

Why Do Illinois Couples Opt To Sign Postnuptial Agreements?

While pre and post-marital agreements often come with a certain amount of stigma, in reality, they can be very effective tools for helping the well-being of the marriage. People turn to postnups in 2026 for a variety of reasons, including the following.

Changes in Financial Circumstances

If one spouse starts a business, receives a large inheritance, or takes on substantial debt, a postnup can dictate how it will affect each person in the event of a divorce. Without an agreement, Illinois law will govern how property is divided. The final decisions made by the court might not reflect what you and your spouse actually want.

Protecting a Business

If one spouse owns a business that grows in value during the marriage, that increased value could be treated as marital property in a divorce. A postnup can specifically designate business assets as separate property. This protects the business owner. In some cases, it can also protect the other spouse from being tied to business debts they didn't agree to take on.

A Prenup Wasn't Considered

Some couples simply don’t consider a prenuptial agreement before the wedding and later wish they had. A postnup can accomplish most of the same goals. If you've been married for a few years and find yourself with more assets, more financial complexity, or are just clearer about what you want, a postnup gives you a second opportunity to plan ahead.

Navigating a Relationship Rough Patch

In some cases, a postnup is used when a marriage is under strain. One spouse may want financial reassurance before committing to staying in the marriage. These agreements can outline what each person will receive if the couple eventually divorces. This can reduce uncertainty and help both parties make informed decisions about the future of their relationship.

Postnuptial agreements require full financial disclosure before signing. The process of going through assets thoroughly and honestly can help many couples build a better foundation, whether they are in relationship difficulties or not.

Do I Need a Lawyer To Draft a Valid Postnuptial Agreement in Illinois?

You don’t technically need a lawyer to create your postnup. However, a postnup is only as good as its drafting. Technical mistakes can invalidate a postnuptial agreement. If the time comes to enforce the postnup, courts will also be on the lookout for evidence that one spouse was pressured into signing or signed without being fully aware of what they were agreeing to. Either of these scenarios can result in the postnup being unenforceable in court.

Because of this, each spouse should have independent legal counsel when drafting a post-marital agreement. If only one attorney is involved, the agreement is more vulnerable to a later challenge. Representation for both spouses makes it much harder to argue that someone didn't understand what they were signing.

Call a Naperville, IL Postmarital Agreement Lawyer Today

Even if you ultimately decide to create a postnup, speaking to an attorney familiar with this aspect of family law can help you make an informed choice. Attorney Don Pesce has nearly two decades of legal experience to lend to your case. Call Pesce Law Group, P.C. at 630-352-2240 to schedule your free consultation with our DuPage County, IL family law attorney today.