Prenuptial & Postnuptial Agreements: What Actually Holds Up in Divorce

A prenup or postnup can be the most important financial document in a divorce — or it can be thrown out entirely. Here is what makes the difference.

What a prenup can and cannot do

A prenuptial agreement can define which assets are separate property and which become marital, set terms for property division, limit or waive spousal support (in most states), address how specific debts will be handled, and protect a family business or inheritance. A prenup cannot determine child custody or child support — courts always decide these based on the child's best interest at the time of divorce.

What gets a prenup thrown out

Courts invalidate prenups more often than people expect. The most common reasons: it was signed under duress or coercion (presented days before the wedding), one or both parties did not have independent legal counsel, there was incomplete or fraudulent financial disclosure, the terms are unconscionable at the time of enforcement, or proper legal formalities were not followed. The closer the signing was to the wedding date, the more scrutiny the agreement receives.

Postnuptial agreements

A postnuptial agreement is the same concept, signed during the marriage rather than before it. Postnups are enforceable in most states, though they may face slightly more scrutiny because the parties are already in a fiduciary relationship. Common reasons to create a postnup include: one spouse received a large inheritance, one spouse started a business during the marriage, or the couple is reconciling after a separation.

The alimony waiver question

Many prenups include a waiver of spousal support. Whether this holds up varies significantly by state. Some states enforce alimony waivers as long as both parties had independent counsel. Others will not enforce a waiver if it would leave one spouse destitute. A waiver that seemed reasonable when both spouses were working professionals may look very different after 15 years where one spouse stayed home to raise children.

Protecting a business

For business owners, a prenup can be critical. Without one, the marital portion of a business — the growth in value during the marriage — may be subject to division. A prenup can specify that the business remains separate property, define how it will be valued if the marriage ends, and limit the other spouse's claim to business assets.

A prenup changes the math of your settlement significantly — but understanding exactly how much requires modeling both scenarios. DivorceSmart Pro lets you compare settlement scenarios side by side to see the financial impact with and without the prenup.

State-by-state variation

Prenup enforceability is highly state-specific. Most states have adopted some version of the Uniform Premarital Agreement Act (UPAA), but the details vary. Some states require both parties to have independent counsel. Some have sunset clause concepts. If you moved to a different state after signing your prenup, the enforceability may be governed by the law of the state where you currently reside.