What Is a Prenuptial Agreement? Everything to Know

Published on October 3, 2023 · 9 min read

Last modified: June 10, 2026

Key takeaways

A prenup—short for "prenuptial agreement"—is a legal contract signed before marriage that defines how property, debt, and support are handled if the marriage ends.
Prenups can protect separate assets, business interests, and inheritance rights, but courts will void any clause that waives child support or violates state law.
You don't have to be wealthy to benefit from a prenup; couples with debt, a family inheritance, a business, or a prior marriage often benefit the most.

What is a prenup?

A prenuptial agreement—commonly called a "prenup"—is a legal contract signed by both partners before they marry. It defines in advance how property, assets, debts, and financial support will be handled if the marriage ends in divorce or death. Both parties must sign it voluntarily, and it takes effect only upon marriage.

The word "prenuptial" simply means "before marriage." The Uniform Law Commission, which drafted the Uniform Premarital Agreement Act that most states use as their legal framework, defines a premarital agreement as a contract made between prospective spouses—written and signed while engaged, with the understanding that it governs what happens to property and support if things don't work out.

A prenup isn't a prediction of divorce. Most couples who sign one never need to use it.

What does a prenup cover?

Prenups are flexible documents—within certain limits—and couples can customize them to reflect their actual financial situation. Most prenuptial agreements address some combination of the following:

Separate vs. marital property

A prenup can specify which assets each spouse owned before marriage and ensure those assets stay separate if the couple divorces. Without a prenup, courts may treat some pre-marital property as jointly owned depending on the state.

Debt allocation

If one partner enters the marriage with significant student loans, credit card debt, or a business liability, a prenup can protect the other spouse from being held responsible for it.

Alimony and spousal support

Couples can agree in advance on whether alimony will be paid, for how long, and in what amount—or waive it entirely, where state law permits.

Business interests

If you own a business, a prenup can prevent it from being divided or disrupted during a divorce.

Inheritance and family wealth

A prenup can protect assets you've inherited—or expect to inherit—so they stay within your family regardless of what happens to the marriage.

Infidelity clauses

Couples can include infidelity clauses in a prenup—they're among the most commonly requested provisions attorneys with Marble encounter. But whether they hold up depends almost entirely on how they're drafted and where you live.

What clients typically want:

"if divorce is initiated due to infidelity, the offending party waives spousal support" or "the cheating party forfeits 70% of their finances." These clauses feel satisfying in theory but are difficult to enforce in practice.

In states like California and Florida, courts operate under a "no fault" divorce framework and don't assign moral blame for a marriage ending. In one California case, an attorney with Marble explicitly cited the no-fault doctrine and rewrote the client's proposed infidelity penalty as a financial adjustment provision—removing the punitive framing while still protecting the client's interests.

In another case in Florida, an attorney with Marble declined to draft the provision at all until researching current state case law—telling the client it would be irresponsible to include the clause without that legal grounding.

In states like Arizona and Texas, fault-based divorce grounds—including adultery—have more legal footing, and support adjustments tied to infidelity can hold up. In one Arizona case, an attorney with Marble successfully drafted an infidelity clause that tied support to a defined threshold rather than a flat asset forfeiture—the kind of structured, proportionate language courts are far less likely to challenge.

The consistent pattern across all states: punitive framing gets challenged. Structured, state-specific language built around your jurisdiction's actual case law is what survives.

What a prenup can't include

This is where many guides—and many couples—stop short. Courts won't enforce every clause in a prenup, and including unenforceable terms can weaken the agreement or get specific provisions thrown out entirely. As Cornell Law School's Legal Information Institute notes, prenuptial agreements are subject to both general contract principles and specific statutory requirements that vary by state—meaning certain categories of provisions are off-limits regardless of what both parties agreed to.

A prenup generally cannot include:

- Child custody or child support terms: Courts determine custody and support based on the child's best interests at the time of the divorce—not based on what two people agreed to before children existed. Any clause that attempts to predetermine custody arrangements or cap child support is typically invalid.
- Provisions that incentivize divorce. If a clause would financially reward one spouse for ending the marriage, courts will usually void it.
- Waiver of the right to legal counsel. Both parties have the right to independent legal advice. A prenup can't eliminate that right, even if one spouse says they don't want an attorney.
- Illegal terms or anything "unconscionable"—meaning so one-sided it shocks the conscience. Courts won't enforce a clause that violates state law or is fundamentally unfair to one party.
- Personal lifestyle clauses. In most states, clauses governing household responsibilities, in-law visits, or personal behavior aren't enforceable—even if both parties agreed to them at the time.

What makes a prenup invalid?

A prenup that's poorly drafted or improperly executed may not hold up when you actually need it. Courts in most states scrutinize prenuptial agreements carefully—and will void them entirely if certain conditions aren't met.

- Signing under pressure or too close to the wedding. If one spouse can credibly argue they signed the prenup days before the ceremony with no real time to review it, courts may treat this as "duress"—meaning they felt pressured or coerced into signing. Timing matters significantly.

"At minimum, 30 to 60 days before the wedding—and more is better," says one attorney with Marble. "The further you are from the ceremony, the harder it is for anyone to argue the signing felt rushed or coerced."

- Incomplete or dishonest financial disclosure. Both parties must fully disclose their assets, debts, and income before signing. If one spouse hid assets or misrepresented their financial picture, the entire agreement may be voidable—even years later.
- No independent legal review. Courts look more favorably on prenups where both parties had their own attorney. If you're unsure whether to hire one, our guide to working with a prenup attorney walks through what to expect. A prenup signed without any legal counsel—especially where one spouse is clearly less financially sophisticated—is more vulnerable to challenge.
- Failure to meet state execution requirements. Depending on the state, a prenup may need to be witnessed, notarized, or executed in a specific format. Missing those formalities can invalidate the agreement regardless of its content.
- According to the American Bar Association, the Uniform Premarital Agreement Act (UPAA)—a model law adopted in some form by many states—sets baseline standards for prenup validity, but execution requirements differ state by state.

Who actually needs a prenup?

One of the most persistent misconceptions about prenups is that they're only for the wealthy. In practice, many couples benefit regardless of net worth.

Prenups are particularly worth considering if:

- One or both of you carries significant debt. Student loans, business debt, or personal credit card balances can become complicated in a divorce. A prenup establishes from day one what belongs to whom.
- You own a business. Without a prenup, your spouse may be entitled to a portion of your business—or its growth in value during the marriage—depending on the state.
- You have children from a prior relationship. A prenup can help ensure your assets pass to your children rather than to a future ex-spouse.
- You expect a family inheritance. A prenup can prevent inherited assets from being classified as marital property in a divorce.
- One of you is remarrying. According to the Pew Research Center, roughly 4 in 10 new marriages in the U.S. involve at least one partner who has been married before—a group that often brings more complex finances to the relationship.

Prenup costs typically range from a few hundred to several thousand dollars depending on complexity and your state—almost always a fraction of what contested divorce litigation runs.

How your state's laws shape your prenup

Prenuptial agreement laws vary meaningfully by state—and where you live determines what a prenup can cover, how it must be executed, and what default rules apply if you don't have one.

Community property states where Marble operates (Arizona, California, Texas): by default, most assets and debts acquired during the marriage are split equally between spouses. A prenup can modify or override this default and protect separate property.

Equitable distribution states (Colorado, Florida, Georgia, Illinois, Maryland, Michigan, New York): courts divide marital property "fairly" but not necessarily equally, at a judge's discretion. A prenup gives both partners more certainty and control over that outcome.

Most Marble states have adopted some version of the Uniform Premarital Agreement Act, which sets a common framework for validity—but execution requirements like witnesses, notarization, and timing differ by state. An attorney with Marble can advise you on exactly what's required where you live.

How a family law attorney can help

A well-drafted prenup is much harder to challenge than one put together from an online template. Here's what an experienced prenup attorney actually does:

- Drafts enforceable language. Particularly around debt allocation, spousal support, and separate property clauses—the areas most commonly contested in a challenge.
- Ensures complete financial disclosure. Proper disclosure is the most common reason prenups survive court challenges. An attorney structures this correctly from the start.
- Advises on timing. Signing too close to the wedding is a red flag for courts. An attorney helps you plan a timeline that protects the agreement's validity.
- Reviews the other side's draft. If your partner's attorney prepared the prenup, having your own counsel review it before you sign is the most important step you can take.

Marble offers prenup drafting and review—no hourly billing, no surprise invoices. See how Marble's family law services work.

Final Thoughts

A prenup isn't about planning for divorce—it's about both partners entering a marriage with their eyes open. Understanding what a prenup does, what it can't do, and what makes one actually hold up in court is the foundation for making a decision that's right for your situation.

If you're already married and missed the window before the wedding, a postnuptial agreement covers much of the same ground. And if you're weighing prenup vs. postnup based on where you are right now, that comparison is a good place to start.

FAQs

Disclaimer: Laws and procedures vary by state and jurisdiction. This article provides general information and should not be considered legal advice for your specific situation. For personalized guidance, consult with an attorney. Attorney advertising.

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What is a prenup?