What is a prenup? What it covers, what it can’t, and how it holds up

A prenup, short for prenuptial agreement, is a written contract two people sign before they marry that sets their own rules for property, debts and spousal support, during the marriage and if it ends in divorce or death.¹ If the word makes you picture a celebrity divorce, here’s the less dramatic version: it’s a plan for money, made while you like each other a lot.

Marriage comes with default rules about money, and a prenup lets you rewrite some of them. The newest model law for these agreements lists what a couple can confirm, change or waive: spousal support, who owns and manages property, who’s responsible for which debts, what happens to property and debts at separation, divorce or death, and even who pays the legal fees.¹

The paperwork side is simple to describe. Almost every state requires a prenup to be in writing, the model law adds that both of you sign it, and it takes effect only if you actually marry.¹ Statutes often call it a premarital agreement, which is the term both the model law and California’s code use.^1,2

Prenups weren’t always this accepted. In the early 1970s, courts generally refused to enforce prenups that changed what happens at divorce. By 2012, when the newest model law was written, every state enforced at least some of them, though the standards vary a lot from state to state.¹

Mostly money: what you each own, what you owe, and what happens to all of it if the marriage ends.¹ California’s law gives one example of what’s on the menu. A prenup there can cover:²

• Property: each person’s rights in anything owned by either or both of you, whenever and wherever it was acquired.²
• Control: who can buy, sell, lease, borrow against or otherwise manage that property.²
• Endings: what happens to property if you separate, divorce or one of you dies.²
• Wills and life insurance: a promise to make a will or trust that carries out the agreement, and who gets a life insurance death benefit.²
• Which state’s law governs the agreement, handy if you move.²
• Anything else, including personal rights and obligations, as long as it doesn’t violate public policy or a criminal law.²

The model law also names debts, so a prenup can say who’s responsible for which liabilities.¹ Couples build in timing, too. Sunset clauses and terms that change with the length of the marriage are common, such as extra rights for a spouse once the marriage passes a set number of years.¹

Spousal support is where states draw different lines. California won’t enforce a spousal support term, including a waiver, if the person giving it up didn’t have their own lawyer when they signed, or if the term is unconscionable when someone tries to enforce it.² And under the model law, if giving up support would leave a spouse eligible for public assistance, a court can order support anyway, to the extent needed to avoid that.¹

A prenup can’t sign away anything that belongs to your kids, and it generally can’t rewrite the basic rules of divorce.¹ Under the newest model law, these terms aren’t enforceable:

• Lowering child support. The right to support belongs to the child, so parents can’t bargain it away.^1,2
• Custody and parenting time. Terms about custody or visitation aren’t binding on a court, which keeps its duty to protect a child’s best interests.¹
• Limiting domestic violence protections. A prenup can’t restrict the legal remedies available to a victim.¹
• Changing the grounds for divorce, or penalizing either of you for filing.¹

Rules about behavior are on shaky ground too. Courts generally won’t enforce prenup terms on topics beyond the money between the two of you,¹ and a California appeals court refused to enforce a married couple’s agreement that a spouse who cheated would pay the other $50,000, because it clashed with no-fault divorce.³

In other words, the everyday stuff (who does the dishes, how often you see the in-laws, how many date nights you get) isn’t what a prenup is built for. Those conversations still matter. They just belong somewhere other than a legal contract.

It depends on your state, but the same questions keep coming up: did you both sign voluntarily, did each of you know what the other owns and owes, was there time to think it over, and could each of you get your own legal advice?^1,4

More than half the states build on one of two model laws from the Uniform Law Commission.⁵ The original Uniform Premarital Agreement Act, from 1983, was adopted in some version by 27 states and the District of Columbia,⁵ and by the drafters’ 2012 count, roughly half of the adopting jurisdictions made significant changes.¹ California adopted it, and under California’s version a prenup isn’t enforceable if the person challenging it proves they didn’t sign voluntarily, or that it was unconscionable when signed and, before signing, they didn’t get fair, reasonable and full disclosure of the other’s finances, didn’t waive that disclosure in writing, and couldn’t reasonably have known.⁴

The newer Uniform Premarital and Marital Agreements Act, from 2012, covers postnups too and adds protections.¹ So far Colorado and North Dakota have enacted it, and a bill has been introduced in Michigan.⁵ Under it, an agreement isn’t enforceable if the person challenging it proves any one of these:¹

• Pressure: their consent was involuntary or the result of duress.¹
• No real chance to get a lawyer: they didn’t have reasonable time to decide on, find and consult a lawyer, or the other partner had a lawyer and they couldn’t afford one and weren’t offered payment for one.¹
• No plain-language warning: they didn’t have their own lawyer, and the agreement included neither the act’s standard notice nor a plain-language explanation of the rights being given up.¹
• No financial disclosure: before signing, they didn’t get a reasonably accurate description and good-faith estimate of the other’s property, debts and income, didn’t waive it in a separate signed document, and didn’t already know.¹

Two details are easy to miss. The model law requires a real chance to get a lawyer, not that you actually hire one. And disclosure doesn’t have to be perfect: a good-faith estimate of value counts even if it later turns out to be wrong.¹

Timing matters, too. In California, for agreements signed since 2020, a prenup is treated as involuntary unless, among other things, the person had at least seven calendar days between first seeing the final version and signing it, and either had their own lawyer or waived one in a separate writing after being advised to get one.⁴ Elsewhere, courts have split: a Washington court found a lopsided agreement involuntary when a significantly revised version arrived three days before the wedding,⁶ while a North Dakota court upheld one presented two days before.⁷

Some states also take a second look at fairness when the agreement is enforced, years after signing. The model law offers that as an option, noting that a significant minority of states allow some form of it.¹

No. In a 2022 Harris Poll survey, 15% of U.S. adults who were engaged or had ever been married said they had signed a prenup, and among those ages 18 to 34 it was 39%.⁸ It wasn’t just high earners, either: people in households earning under $50,000 reported signing one at the same rate (15%) as people in households earning $100,000 or more.⁸

Whether you need one is a question for the two of you (and, if you go ahead, a lawyer in your state). It’s worth talking through if either of you owns a business or a home, expects an inheritance, has kids from a previous relationship, is bringing significant debt, or plans to step back from paid work to care for family.

A postnup, or postnuptial agreement, is the same kind of contract signed after the wedding by spouses who plan to stay married.¹ Under the model law, changing a prenup after you marry counts as one too, and like the original, any change has to be in writing and signed by both of you.¹

The big difference is how hard courts look at it. Their reasoning goes like this: before the wedding, either of you can walk away from a deal you don’t like. Once you’re married, you owe each other a higher duty of loyalty, and one spouse could use the threat of divorce as leverage. That’s why many states scrutinize postnups more closely, and a few put the burden of proof on the spouse who wants one enforced.^1,9

Massachusetts shows what that looks like. In 2010 its highest court held that postnups can be enforced, but only after a judge checks that each spouse had a chance to get their own lawyer, there was no fraud or coercion, both fully disclosed their assets, each knowingly waived their rights in writing, and the terms were fair and reasonable both when signed and at the time of divorce.⁹ The spouse who wants the postnup enforced has to prove all of it.⁹

Postnups haven’t always been allowed everywhere. Until March 2023, Ohio law said spouses couldn’t change their legal relations by contract with each other, except to agree to an immediate separation.¹⁰ Ohio now permits postnups that are in writing, signed by both spouses, entered freely without fraud or coercion, based on full disclosure (or full knowledge) of both spouses’ property, and don’t encourage divorce.¹¹

The 2012 model law takes the opposite view and applies the same rules to prenups and postnups, as do many other states and the American Law Institute.¹ Postnups can come up for the same reasons as prenups, or when something changes after the wedding, like an inheritance or a new business.

Prenups and postnups are legal contracts about money and property, signed before or after the wedding.¹ A relationship contract like The Couples Contract is a written agreement about everyday life, and it isn’t legally binding at all.

People use “relationship contract” loosely for any written agreement about how a couple wants life to work. Ours, The Couples Contract, isn’t legally binding and doesn’t replace a prenup. It’s a guided way to agree, in writing, on the things a prenup isn’t built for: who handles which chores, who pays for what day to day, holidays and in-laws, and where and how you have the hard talks.

Some couples decide a prenup isn’t for them, and some want both: a prenup for the legal side and a relationship contract for the daily one. Living together first? Our guide to cohabitation agreements covers the unmarried side.

Bring it up early, frame it as a decision you make together, and start with the money conversation rather than the document. Nobody wants to hear the word “prenup” for the first time the week of the wedding.

1. 1

   Start early

   Months before the wedding, not days. It takes the pressure off, and as you saw above, timing can matter legally too.

2. 2

   Lead with why

   Say what you want it to do for both of you: clarity, fairness, no surprises. Not what you’re afraid of.

3. 3

   Put everything on the table

   What you each own, owe and earn, plus anything you expect, like an inheritance. Our money questions for couples make a good warm-up.

4. 4

   Talk about fair before you talk about terms

   What would feel fair to each of you if your lives changed? Start with the principle; the details come later.

5. 5

   Then bring in a lawyer

   A family lawyer in your state can explain how the rules work where you live and what your agreement would need.

What does a prenup cost? It varies a lot. The big drivers are whether you each hire your own lawyer, how complicated your finances are (a business, real estate, trusts), how much back-and-forth it takes, and where you live.