When most people think about “marriage contracts,” they picture prenups, the agreements couples sign before getting married. But life happens, and for many couples, a postnup (aka “marital agreement”) becomes an important legal tool after the “I do.” Many circumstances can trigger the desire for a postnup, like having children, changing jobs, second marriages, starting a business or receiving an inheritance. There are countless reasons why married couples might want to be on the same page financially speaking. If you’re exploring a postnup, you’re probably encountering a lot of legalese in your research. This glossary will help you cut through the fog and understand the key terms you’ll see in postnuptial agreements. But, aside from timing, how is a postnup different than a prenup? And, how is property divided in a divorce if you don’t have a prenup? Keep reading to find the answers to your questions. Whether you’re just beginning your research or already talking to a lawyer, this guide is for you.
Postnuptial agreement
Let’s define the most important term first. What exactly is a postnup? A postnuptial agreement is a legal contract entered into by spouses after they get married. Like a prenup, it outlines how assets, debts, income, and potentially spousal support will be handled in the event of a divorce or death. Some couples also use it to document how they plan to handle finances during the marriage. It’s important to know that enforceability varies by state, so a postnup that flies in California might be tossed out in New Jersey.
Fiduciary duty
Courts tend to give postnups the side-eye a little more than prenups or other contracts, and there’s a good reason. By the time you’re signing a postnup, you’re already married, which means you’re in a legally recognized relationship of trust and loyalty. That creates what the law calls a fiduciary duty between spouses. This is a heightened obligation to be completely honest and fair with one another. In practical terms, courts assume that one spouse might have more leverage in the relationship or that subtle pressure could be at play. So, judges go the extra mile to make sure the agreement wasn’t signed under coercion, unfair surprise, or incomplete financial disclosure.
This extra scrutiny also stems from the fact that postnups can directly alter the legal rights a spouse already has under marriage and divorce laws. When you’re dating or engaged, you don’t yet have marital property rights, so prenups are more about setting expectations for the future. But with a postnup, you’re potentially giving up rights you already own. That’s why courts often look closely at whether the terms were procedurally fair (how the agreement was negotiated) and substantively fair (whether the outcome itself is reasonable). In many states, the bar for enforcing a postnup is higher than for a prenup. This is not because the law is against them, but because it’s protecting both spouses from being taken advantage of after the wedding bells have rung.
Default property division laws
Without a postnup or prenup, your property will be divided according to your state’s default property division laws, which are basically the state’s standard playbook for who gets what in a divorce. Nine of the states in the United States divide property in a divorce according to the principles of community property. This means that property earned or acquired during marriage is presumed to be marital property and is subject to equal division during a divorce. The rest of the states distribute property based on the principle of equitable distribution. This means that courts will divide property based on what’s fair and just, not necessarily 50/50. A postnup allows you to override your state’s default laws. But again, fairness matters. Courts want to make sure one spouse isn’t taken advantage of, especially if there’s a power or income imbalance.
Separate property
Separate property is the “what’s mine is mine” category of assets in a marriage. In most states, it includes anything you owned before you walked down the aisle, as well as inheritances and gifts you receive during the marriage. The idea is that these items are yours alone and are safe from division during divorce unless you inextricably mix, or “commingle,” them with marital property. A court can change the classification of an asset from separate to marital based on how you treated that separate property during marriage.
This is where it gets tricky. What counts as separate property, and how it’s treated, can vary dramatically by state. In community property states like Texas or Arizona, the rules for keeping something separate are strict. You usually have to be able to trace the asset directly back to its original, separate source. In equitable distribution states like New York or Illinois, the concept is similar, but judges may have more leeway in deciding how it’s divided if separate and marital property become tangled.
For example, if you owned a condo before marriage but then used marital funds for renovations or mortgage payments, some or all of the condo’s value could shift into from the “separate” column into the “marital” column. This is where a postnup comes in handy! This agreement can explicitly state what stays separate and what becomes joint property, reducing confusion (and courtroom drama) later. Another important topic to include when discussing separate property is appreciation.
Appreciation is the increase in value of an asset. A well-drafted postnup will always address appreciation. If your separate property gains value during the marriage, say, your premarital stock portfolio doubles in size, some states may treat that growth as marital property, depending on whether it was due to market forces or your active efforts. Without a clear agreement stating how you plan to classify appreciation during a divorce, this is one of the most common areas where couples end up in disputes.
Marital property (aka “community property”)
The name of these assets depends on where you live. In equitable distribution states, joint assets might be called “marital property.” In community property states, they are regularly referred to as “community property.” Marital or community property is defined as everything earned or acquired during the marriage, including income, houses, retirement savings, and more. A postnup can redefine what’s considered marital property based on the desires of the couple. But, understand that even with a signed contract agreeing how property should be classified, courts will still scrutinize whether the postnup was executed fairly and transparently.
Spousal support (aka “alimony”)
Spousal support, also called alimony in some states, is money paid by one spouse to the other after a divorce. A postnup can address this either through waiving it entirely or agreeing on a specific amount or duration. But not every state will enforce a waiver of spousal support. For example, California will not enforce spousal support waivers unless the waiving party had independent counsel and the terms aren’t unconscionable at enforcement (Cal. Fam. Code § 1612(c)). Texas, on the other hand, is more lenient when enforcing spousal waivers, but still requires full and fair financial disclosure and of course voluntary signatures (Tex. Fam. Code § 4.003).
Full financial disclosure
A financial disclosure in the context of a postnuptial agreement is essentially a full, honest, and detailed “here’s everything I have and owe” list from each spouse. That means laying out all assets such as bank accounts, retirement funds, real estate, business interests, and valuable personal property as well as debts, including mortgages, credit card balances, student loans, and any other liabilities. In many states, this disclosure must be in writing and attached to the agreement, or at least provided in a way that leaves no doubt the other spouse understood your financial picture before signing.
The reason disclosures matter so much is that a postnup often changes how these assets and debts will be handled if you divorce or if one spouse passes away. Courts want to be sure both parties negotiated with their eyes wide open. If one spouse hides significant assets or undervalues them, that’s a fast track to the agreement being tossed out. Some states allow spouses to waive detailed disclosures if both agree they already have “adequate knowledge” of each other’s finances. Still, that waiver itself can be risky, especially if one spouse later claims they didn’t really know the full scope of the other’s wealth. Think of it this way: a valid postnup is built on trust, and the financial disclosure is the foundation. If that foundation has cracks because of incomplete or inaccurate information, the whole agreement can crumble in court.
Consideration
In contract law, “consideration” is the legal way of saying that each party to an agreement has to give something of value in exchange for what they’re getting. With prenuptial agreements, consideration is usually built in because the marriage itself is the “something of value” that makes the contract enforceable. Postnuptial agreements, however, happen after the wedding, so marriage can’t be used as the consideration anymore. That means each spouse needs to bring something new to the table for the postnup to be valid in most states.
Consideration in a postnup might look like one spouse agreeing to transfer certain property, take on a particular debt, or make a financial concession in exchange for the other spouse agreeing to a specific property division or spousal support arrangement. Sometimes the “value” is more practical than monetary, but courts tend to look for something tangible. This matters because a court can treat the agreement as a one-sided promise rather than a binding contract if there’s no valid consideration. In other words, without that exchange of value, the postnup could be unenforceable no matter how well it’s drafted. And because postnups are already held to a higher level of scrutiny than most contracts, weak or missing consideration is one of the fastest ways to see your agreement invalidated.
Independent legal counsel
Many states don’t require that each party have their own independent attorney, but all states strongly recommend it. Courts look more favorably on postnups where both parties had their own lawyers. Separate legal representation shows the court that both sides had a professional walk them through the language of the agreement and explain the potential legal and financial consequences before each party signed. Since voluntary signatures are a requirement for postnups, it’s clear to see the benefit of having independent legal counsel.
Unconscionability
Unconscionable is the legal term for “shockingly unfair.” If a postnup is so one-sided that a court thinks it’s unjust, it can be ruled unconscionable and thrown out. Some states view postnups with heightened scrutiny compared to other states. And since postnups are signed when the parties are already married, and therefore in a fiduciary relationship, courts are often more willing to revisit fairness at the time of enforcement.
For example, a Massachusetts court in the case Ansin v. Ansin, explicitly applied a “second look” to postnups, meaning that courts in this state will assess fairness at both signing and enforcement. Connecticut and New Jersey have similar case law showing the courts in these states are likely to consider whether the terms of a postnup are fair at signing and at the time of enforcement.
Voluntariness
As discussed above, a postnup has to be signed voluntarily for it to be valid and enforceable. This means that both parties had to have signed the postnup freely without pressure or coercion. This doesn’t just mean physical force, it includes emotional pressure or time constraints. If one spouse signed under duress, or without time to review the agreement, the court might not enforce it. This is especially important if the agreement was presented during a rocky period in the marriage or right after a major life event.
Governing law clause
This clause specifies which state’s laws will apply to the agreement. This provision is crucial if you’ve moved or anticipate moving. Let’s say you drafted a postnup in Illinois, but later moved to Georgia. A well-written governing law clause could help ensure that Illinois law still applies to the agreement, assuming both spouses agree. But be careful, not every state will honor another state’s laws if it violates local public policy. Talk with an attorney about your choice of law clause to make sure your agreement abides by the laws of the state that will govern.
Sunset clause
A sunset clause is a provision that says the postnup or specific provisions of the contract will expire after a certain number of years or upon the occurrence of a specific event, like the birth of a child. The idea is that a couple’s financial circumstances and relationship dynamics can change over time, and a provision that seemed fair early in the marriage might not make sense decades later. By building in an expiration, the agreement forces a revisit and renegotiation, ideally when both spouses are still on good terms. This provision is optional, but a great way to build flexibility into the agreement.
Severability clause
You will find severability clauses in most contracts. This clause protects the rest of the agreement if one part is later deemed unenforceable. So, if a court finds the alimony waiver invalid, for instance, the rest of the postnup can still stand. Think of it as the legal version of “don’t throw the baby out with the bathwater.” From a legal standpoint, severability clauses show intent. They make it clear that you and your spouse wanted the valid parts of the postnup to survive even if one part doesn’t. Courts often look for that intent when deciding whether to enforce the remaining provisions. Some states, especially those that scrutinize postnups more closely than prenups, will enforce severability clauses as long as the remaining terms still make sense on their own and don’t fundamentally change the bargain between spouses. In other words, the “meat” of the agreement must remain intact.
Final thoughts on postnup terms
Postnups aren’t just for the rich or for couples in crisis. They’re for anyone who wants clarity, peace of mind, and control over their financial future. But like any legal contract, they come with rules that vary across state lines. If you’re considering a postnup, talk with an attorney in your state who has experience drafting postnuptial agreements. And make sure that you and your spouse understand what you’re signing. These agreements are meant to support your marriage, not undermine it.
Jourdan Stewart is Legal Operations Attorney at HelloPrenup, and a Texas licensed attorney. Jourdan is experienced in drafting prenuptial agreements, and her legal expertise extends to other aspects of family law, business law and entertainment law. Jourdan earned her law degree from Pepperdine University, her MBA from The Acton School of Business, and her BBA from Baylor University. Jourdan’s favorite aspect of legal practice is helping clients fully understand and achieve their goals. She finds great satisfaction in tailoring solutions to each client’s unique set of wants and needs. When she’s not practicing law, Jourdan can be found in nature with her two children and their dog, Stewey.
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