How Do Postnuptial Agreements Work in Illinois?

 Posted on July 04, 2025 in Postnuptial Agreements

Handling financial matters during marriage can be complex. Couples often seek ways to protect their assets and plan for the future. A Naperville, IL postnuptial agreement lawyer can help you understand how a postnuptial agreement, also known as a postnup, works under Illinois law. Signing a postnup does not indicate that you think your marriage will fail. It is just a contract between two financially responsible adults.

What Conditions Can Be Included in a Postnuptial Agreement in Illinois?

Like a prenuptial agreement, a postnuptial agreement defines how property and maintenance are handled during divorce. The primary difference is that you sign a prenup before marriage and a postnup when you are already married. Section 750 ILCS 5/503 of the Illinois Marriage and Dissolution of Marriage Act states that marital property is divided fairly, not always equally, in divorce. However, prenups and postnups allow you to have more control over the process.

Specific conditions you can include in a postnup are:

• How assets, such as real estate, cars, and investments, will be divided

• Ownership rights and income from a business

• Who will be responsible for specific debts and liabilities

• Whether either spouse will pay spousal maintenance, commonly known as alimony

• How to divide retirement accounts

• How to handle disputes

Postnups cannot decide child custody or child support in advance. Those issues are determined based on the child’s best interests at the time of separation or divorce.

What Are the Advantages of a Postnuptial Agreement in Illinois?

A postnuptial agreement is beneficial under several common circumstances. Sometimes, spouses who are working together to repair their relationship decide to put financial protections in place. Additionally, one spouse may receive an inheritance during the marriage. They can use a postnuptial agreement to protect that inheritance during a potential divorce. In some cases, outside expectations can play a role in a couple’s decision to enter into a postnup. For example, if one spouse becomes involved in a family-owned business, they may be required to draft a postnup to protect the business.

Modification of a prenup is another common reason for a postnuptial agreement. If you already have a prenuptial agreement and want to amend it later, the only way to do so while married is through a postnup. Section 750 ILCS 10/6 of the Illinois Uniform Premarital Agreement Act states that a written agreement signed by both parties is required to amend a prenuptial agreement during marriage. 

Can a Postnuptial Agreement Be Challenged in Illinois?

Grounds for challenging a postnup are the same as the grounds for challenging a prenup. If one spouse was coerced or forced to sign against their will, they can challenge the agreement. The same is true if one spouse misrepresented their assets or liabilities when the agreement was signed. A common argument against enforcing a prenup or postnup is unconscionability. This is addressed under Section 750 ILCS 10/7(a) of the Uniform Premarital Agreement Act. It states that the contract is not enforceable if the terms are so one-sided that it would be shocking to the court’s conscience to enforce it. Essentially, the terms of your postnup have to be fair, or it will not be enforced by the court.

Contact a Naperville, IL Postnuptial Agreement Attorney Today

Protecting your financial future and maintaining clarity in your marriage starts with understanding your legal options. Talk to a DuPage County, IL postnuptial agreement lawyer at Calabrese Associates, P.C. to ensure your contract is carefully drafted and enforceable. Call 630-393-3111 to schedule a confidential consultation.