Legal guide
Postnuptial agreements: requirements, enforceability, and case law
A plain-English legal guide to how postnups work in the United States, what courts look for before they will enforce one, and how the law differs from prenups.
In plain English
A postnuptial agreement, or postnup, is a written contract a couple signs after they are already married. It sets out how the couple will divide assets, debts, and property, and in many states whether spousal support is paid, if the marriage later ends. The same kind of contract signed before marriage is a prenup.
- Signed after marriage, while a prenup is signed before
- Enforceable in most states when done correctly
- Reviewed more closely by courts than a prenup
- Cannot decide child custody or child support
The difference
Prenup vs postnup, legally speaking
A prenuptial agreement and a postnuptial agreement do the same job: they let a couple decide in advance how property, debt, and support will be handled if the marriage ends. The practical difference is timing. The legal difference is how closely a court will look at the agreement, which we cover in the next sections.
| Prenuptial agreement | Postnuptial agreement | |
|---|---|---|
| When signed | Before marriage | After marriage |
| Takes effect | On the wedding day | On signing, once married |
| Court scrutiny | Standard contract review | Often heightened scrutiny |
| Recognized | In every US state | In most, but not all, states |
| Common purpose | Set terms before the marriage starts | Add clarity after a change in circumstances |
Why couples get one
Common reasons couples get a postnup
A postnup is not a sign of trouble. Most couples use one to get on the same page about money and protect each other. These are the situations that most often lead a married couple to put one in place.
You skipped a prenup
You ran out of time before the wedding, or simply decided against a prenup then, and now want that same clarity and protection.
One of you owns a business
A spouse started or grew a company and wants to define how the business, and its growth during the marriage, is treated.
An inheritance or large gift
You are expecting or received an inheritance or significant gift and want to keep it as separate property.
Your finances changed
A major shift in income, assets, or debt since the wedding makes it worth putting clear terms in writing.
One spouse steps back from work
When one partner pauses a career to raise children or support the household, a postnup can protect that contribution.
A financial fresh start
Some couples use a postnup to reset expectations and rebuild trust around money, including after working through a rough patch together.
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The legal test
What makes a postnup enforceable
Rules vary by state, but courts across the country tend to look for the same core elements before they will uphold a postnuptial agreement. Missing one of these is the most common reason a postnup is challenged or set aside.
In writing and signed
A postnup must be a written contract signed by both spouses. Many states also expect it to be notarized, and some require witnesses.
Voluntary, no coercion
Each spouse must sign freely. Pressure, threats, or signing under duress can render the agreement unenforceable.
Full financial disclosure
Both spouses must fairly disclose assets, debts, and income. Hidden assets are one of the fastest ways to void a postnup.
Fair, not unconscionable
The terms should be fair to both spouses. Courts can decline to enforce an agreement that is grossly one-sided.
Opportunity for counsel
Each spouse should have the chance to consult an independent attorney. Some states require it, and it strongly supports enforceability everywhere.
Within legal limits
A postnup cannot decide child custody or support and cannot include terms that are illegal or against public policy.
Why postnups are different
Courts hold postnups to a higher standard
This is the single most important thing to understand about postnups. Before marriage, two people negotiate at arm's length and either one is free to walk away. After marriage, the law treats spouses as being in a confidential relationship in which they owe each other a duty of good faith and fair dealing. One spouse may also have far more financial leverage than the other.
Because of that imbalance, many courts review a postnup more carefully than a prenup. They look harder at whether disclosure was complete, whether both spouses truly understood and freely accepted the terms, and whether the result is fair. Several state high courts have said outright that postnuptial agreements deserve this closer look.
Practical takeaway: the safest postnup is one where both spouses fully disclosed their finances, each had their own attorney, and neither was rushed. That is exactly the process Postnup.com is built around, with a licensed attorney included for each partner.
Governing law
The statutes and uniform law behind postnups
Most postnup law is made by state courts rather than a single national statute, which is why enforceability and standards differ from state to state. There is, however, a modern uniform law aimed at harmonizing the rules.
The Uniform Premarital and Marital Agreements Act (UPMAA), finalized in 2012, was the first uniform act to cover marital, that is postnuptial, agreements alongside premarital ones, and it sets out shared standards for disclosure, voluntariness, and unconscionability. A small number of states have adopted it, while the rest continue to rely on case law and general contract principles. Its predecessor, the Uniform Premarital Agreement Act (UPAA), addressed only prenuptial agreements, which is part of why postnup law developed later and less uniformly.
Because the governing law is state specific, the same agreement can be treated differently in different states. Always confirm the current rules in your state with a licensed attorney.
Scope
What a postnup can and cannot include
Can include
- Division of marital and separate property
- How debts are handled and assigned
- What happens to a home or real estate
- Ownership and growth of a business
- Inheritances and gifts kept as separate property
- Spousal support, in many states
Cannot include
- Child custody arrangements
- Child support amounts
- Anything illegal or against public policy
- Personal or lifestyle clauses a court will not enforce
- Terms designed to encourage or plan a divorce
Avoid these
Common mistakes that void a postnup
Most postnups that fail in court fail for the same handful of reasons. Steering clear of these is the difference between an agreement that holds up and one a judge sets aside.
Hiding or lowballing assets
Incomplete or inaccurate financial disclosure is the fastest way to get a postnup thrown out. Both spouses must lay it all out.
Signing under illegal pressure
Rushing your spouse, or presenting the agreement as an ultimatum, can make a court find it was not entered into voluntarily.
No time to review or get advice
Denying a spouse the chance to read the agreement or consult their own attorney undermines enforceability.
Wildly one-sided terms
An agreement so lopsided that it leaves one spouse with almost nothing can be struck down as unconscionable.
A generic template
Language that does not meet your state's specific requirements may not survive review, which is why state-specific drafting matters.
Signing on the courthouse steps
An agreement put in place right before a divorce filing can be challenged as divorce planning and disregarded.
Ready to start your postnup?Postnup.com handles your agreement end to end, online, with an attorney for each of you.
Get your postnup at Postnup.comBy state
Postnup law is state specific
Whether a postnup is recognized, and how strictly it is reviewed, depends on where you live. Postnups are recognized in most states, and a few, including Massachusetts, Connecticut, and New Jersey, apply heightened scrutiny. We publish detailed, attorney-reviewed guides for individual states.
Case law
Cases that shaped postnup enforceability
Because postnup law is largely built by state courts, a handful of decisions are frequently cited for how they treat enforceability and scrutiny. The summaries below describe the general principles these cases are known for and are not legal advice.
Massachusetts · 2010
The Massachusetts high court confirmed that marital, that is postnuptial, agreements can be enforced, and set out factors courts should weigh, including full disclosure, the opportunity for independent counsel, the absence of fraud or coercion, and whether the agreement is fair and reasonable.
Connecticut · 2011
The Connecticut Supreme Court recognized postnuptial agreements but made clear they are subject to special scrutiny, holding that a postnup must be fair and equitable when signed and not unconscionable at the time enforcement is sought.
New Jersey · 1999
A New Jersey court applied a more demanding standard to a mid-marriage agreement than would apply to a prenup, reflecting the view that an agreement between spouses calls for closer review than one between engaged partners.
Case law changes and varies by jurisdiction. For how these principles apply to your situation, consult a licensed attorney in your state.
Still have questions?
Book a free 20-minute consultation with our team. We'll walk you through anything specific to your state, your situation, or the product.
Frequently asked
Postnuptial agreement questions
A postnuptial agreement, or postnup, is a written contract a couple signs after they are already married. It sets out how the couple will divide assets, debts, and property, and in many states whether spousal support is paid, if the marriage later ends in divorce or one spouse passes away. A prenup does the same thing but is signed before marriage.
In most states, yes, when they are done correctly. Courts generally enforce a postnup that is in writing and signed by both spouses, entered into voluntarily, based on full and fair financial disclosure, and fair rather than unconscionable. A few states do not clearly recognize postnups, and rules vary, so you should review your agreement with a licensed attorney in your state.
The practical difference is timing: a prenup is signed before marriage and a postnup after. The legal difference is scrutiny. Once a couple is married, the spouses owe each other a duty of good faith, so many courts review a postnup more closely than a prenup to confirm it is fair and was entered into without pressure.
Before marriage, two people negotiate at arm's length and can walk away. After marriage, spouses are in a confidential relationship and one may have more leverage, so courts look harder to make sure a postnup is fair, fully disclosed, and free of coercion. Several state high courts have applied this heightened standard to postnuptial agreements.
Independent legal representation is not required in every state, but having a separate attorney for each spouse strongly supports enforceability and is required in some states. This is why Postnup.com, HelloPrenup's sister brand, includes a licensed attorney for each partner with every postnup.
Yes. A court can refuse to enforce a postnup if a spouse hid assets, if one spouse was pressured or coerced into signing, if there was no meaningful chance to review it or get advice, or if the terms are so one-sided that they are unconscionable. Agreements signed right before a divorce filing can also be challenged as divorce planning.
A postnup can address division of marital and separate property, debts, a home, a business, inheritances and gifts, and in many states spousal support. It generally cannot decide child custody or child support, because courts decide those based on the child's best interests at the time, and it cannot include terms that are illegal or against public policy.
HelloPrenup focuses on prenuptial agreements. Postnuptial agreements are offered by our sister brand, Postnup.com, which provides a state-specific postnup with two attorneys, e-signature, and online notarization included, for a flat $2,499 per couple.
Costs vary. A traditional postnup through a law firm often runs $5,000 to $25,000 because each spouse hires their own attorney. Postnup.com, HelloPrenup's sister brand, offers a state-specific postnup with two attorneys and online notarization included for a flat $2,499 per couple.
Generally no. A postnup stays in effect until the couple revokes or amends it in writing, or a court declines to enforce it. Some couples build in their own review or sunset terms, but a postnup does not expire on its own.
In many states a postnup can address or waive spousal support, but rules vary and some states scrutinize support waivers closely. A court may decline to enforce a waiver it finds unfair at the time of divorce, so review any support terms with a licensed attorney in your state.
A postnup is signed by a married couple who intend to stay together and want to plan how finances would be handled if the marriage later ends. A separation agreement is signed when a couple is separating or divorcing and is settling the terms of that split. The timing and intent are different, and courts treat them differently.
With an online service like Postnup.com, most couples finish in about 2 to 10 days, depending on how quickly both partners complete their questionnaires and meet with their attorneys. A traditional law firm postnup often takes 2 to 3 months.
For many couples, yes. A postnup gives clarity and peace of mind about money, protects each spouse, and can reduce conflict if the marriage ends. Whether it is right for you depends on your assets, your goals, and your state's rules, which a free consultation can help you think through.
About the reviewer
Nicole Sheehey, Esq.
Head of Legal at HelloPrenup
Nicole is a licensed attorney and the Head of Legal at HelloPrenup, where she oversees the legal accuracy of HelloPrenup and Postnup.com agreements and educational content. She reviewed this guide for accuracy. Learn more about Nicole.
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HelloPrenup is the premier online platform for affordable, attorney-backed prenuptial agreements. Postnuptial agreements are offered by Postnup.com, a HelloPrenup, Inc. brand. HelloPrenup is not a law firm and does not provide legal advice or representation. This guide is for general information only and is not legal advice, and case summaries describe widely cited principles rather than the holding for your situation. Postnuptial agreement law varies by state and changes over time. For advice about your specific situation, consult a licensed attorney in your state. Information is current as of June 10, 2026.