Key Differences Between Illinois Prenups and Post-nups

Illinois Premarital Agreements

Most people have heard of premarital agreements (often referred to as “prenups”).  The law defines prenups as contracts drafted and signed by a couple prior to their marriage.  Illinois has a statute, known as the Illinois Uniform Premarital Agreement Act, which provides the framework for prenups.

Even though prenups are fairly common, the law of Illinois has limitations on what terms are enforceable in a prenup.  For example, an Illinois prenup cannot allocate parenting rights, parenting time or child support.  Parenting issues and child support must be decided in the best interest of the child.

Illinois Post-nuptial Agreements

Most people are not as familiar with post-nuptial agreements (“post-nups”) as they are familiar with prenups.  Contracts that between a couple after they marry are post-nuptial agreements. Even though prenups and post-nups are both contracts between couples, they are very different from each other.  Some people, even some family law attorneys, mistakenly view post-nups as essentially prenups that a couple did not get around to signing until after the wedding.  But that is not the case.  Illinois law treats post-nuptial agreements very differently than prenups.

Legal Consideration

One reason for this disparate treatment is that all contracts must have sufficient legal consideration in order to be enforceable.  Consideration is something of value that is exchanged for the performance or promise of performance by the other party.  For example, in a painting contract, the consideration that the homeowner provides is the payment of the painter’s fee.  The consideration the painter provides is the promise to paint the house in a workmanlike fashion.

With prenups, agreeing to marry someone is legal consideration.  Marriage provides significant legal and financial benefits.  With post-nups, the challenge is that spouses are already in a fiduciary relationship with each other.  To a large extent, when a couple marries they become “one” in the eyes of the law.  After marrying, the couple’s income, property and debts can be deemed “marital property” and not individually-owned property.

When parties to a contract negotiate and bargain “at arm’s length”, it indicates that there is sufficient consideration. Why would a painter spend days or weeks painting your house if you were not paying him or her a reasonable fee?  With married couples, the waters are clearly a lot murkier.  Love between spouses is not sufficient legal consideration for a contract.   That said, divorce attorneys can advise their clients how to provide legal consideration in a post-nuptial agreement.

Maintenance Terms

Another key difference between an Illinois prenup and an Illinois post-nup, may be terms about maintenance (“alimony”).  Illinois prenups can include maintenance terms.  There is not an Illinois statute for post-nups like there is for prenups.  The statutory authority for a post-nuptial agreement is a brief reference contained in the property section of the Illinois Marriage and Dissolution of Marriage Act.   Because the authority for post-nups is in the property section, it provides for agreements regarding property.  Generally, Illinois law does not categorize maintenance as property.  The IMDMA contains a section on maintenance that is separate from the property section.  Thus, there is a legal argument that an Illinois post-nuptial agreement cannot include maintenance terms.  Since maintenance is often a substantial amount of money, the risk that it may not be an enforceable term in a post-nup is a significant disadvantage of post-nups.

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If you are looking for legal advice and representation with an Illinois divorce, schedule a consultation with experienced Chicago divorce attorney, Tanya Witt, at (312) 500-5400 or

Representing men and women in Chicago divorce and child custody cases.

This blog does not constitute legal advice. Please consult with an attorney regarding your specific case.