A prenuptial agreement can decide who keeps which property and debts, how income earned during the marriage is treated, whether either spouse pays alimony, and how assets pass at death. What a prenup can and cannot include is set partly by contract law and partly by statute: about half the states have adopted some version of the Uniform Premarital Agreement Act, which draws the outer limits. Inside those limits there is real flexibility. Outside them — child custody, child support, and most lifestyle rules — a clause is unenforceable no matter how carefully it is written.
Property, Debt, and Income
The core function of a prenup is to draw a line between separate and shared property. Without one, most states apply default rules that treat anything earned or acquired during the marriage as jointly owned. A prenup can override those defaults and address the rights and obligations each spouse has in any property either of them owns, whenever and wherever it was acquired, and how property will be divided on separation, divorce, or death.
In practice, this means you can designate a home, a brokerage account, or a business owned before the wedding as separate, along with any future appreciation in its value. The same works for debt. Student loans or credit card balances one person brings into the marriage can be assigned to that person alone, so the other spouse is not on the hook if the marriage ends.
Income earned during the marriage can also be reassigned. In community property states, wages earned after the wedding are split equally by default. A prenup can change that and designate each spouse’s earnings as their own separate property. This is one of the most heavily negotiated provisions, because over a long marriage the financial consequences are large.
Spousal Support
Alimony is one of the most negotiated parts of any prenup. The agreement can set a formula, such as a fixed monthly amount that increases with each year of marriage, or it can waive spousal support entirely. Courts in most states will honor these terms. There is one important exception: if enforcing an alimony waiver would leave one spouse unable to support themselves and eligible for public assistance, a judge can override the waiver and order support. That safeguard applies even in states that otherwise give broad latitude to prenup terms.
Inheritance and Life Insurance
Under most state laws, a surviving spouse has the right to claim a portion of the deceased spouse’s estate regardless of what a will says. A prenup can waive that right. This is one of the main reasons couples with children from a prior relationship sign one: the waiver lets specific assets pass to those children instead of being pulled into the surviving spouse’s elective share. The agreement can also address ownership rights in life insurance death benefits and specify which policies are designated for which beneficiaries.
Sunset Clauses
Some couples include a sunset clause, which causes part or all of the prenup to expire after a set period or a triggering event. A common version terminates certain provisions on the 10th or 15th wedding anniversary; others are tied to specific events, like the birth of a child. Once the trigger date passes, the expired provisions generally stop being enforceable, though the clause typically will not kick in if a divorce is already underway.
Child Custody and Child Support Cannot Be Decided in Advance
A prenup cannot predetermine custody or reduce a child’s right to financial support. The Uniform Premarital Agreement Act states this explicitly: a child’s right to support may not be adversely affected by a premarital agreement. Courts decide custody and support based on the child’s best interests at the time of the proceedings, using current circumstances rather than terms a couple agreed to years earlier, sometimes before the child was born. Any provision that tries to lock in custody or cap child support below what a court would order will be thrown out.
Lifestyle and Behavioral Clauses
Infidelity penalties, weight requirements, restrictions on social media posts, rules about intimacy, and clauses dictating time spent with extended family have all appeared in prenups. Their enforceability is shaky. Courts generally treat lifestyle clauses as personal rather than legal matters, and judges frequently refuse to enforce provisions they view as controlling behavior rather than protecting financial interests. Including unenforceable lifestyle clauses can also raise questions about whether the rest of the agreement was negotiated in good faith, so they carry a cost beyond simply being ignored.
Why an Otherwise Valid Clause Can Still Fail
A signed prenup is not automatically enforceable. If one spouse challenges it during a divorce, a court will look at how the agreement was made and whether its terms cross the line into unfairness. The analysis usually comes down to three questions.
Was It Voluntary?
Both parties must have signed freely, without pressure or coercion. The classic scenario that gets prenups thrown out is one spouse presenting the agreement for the first time days or hours before the wedding, when the other person feels they have no real choice. Some states address this directly. California requires that the final draft be in the parties’ hands for at least seven days before signing. Most states have no specific waiting period, but judges look skeptically at agreements signed under time pressure close to the ceremony.
Was There Adequate Financial Disclosure?
A prenup is only as solid as the financial information behind it. Both parties must provide a fair and reasonable disclosure of their assets and debts before signing. Hiding a retirement account, undervaluing a business, or omitting a significant asset gives the other spouse grounds to void the agreement. Under the Uniform Premarital Agreement Act framework, a challenger can defeat enforcement by showing they were not given adequate disclosure, did not waive disclosure in writing, and did not have independent knowledge of the other person’s finances. In practice this means compiling bank and investment statements, real estate values, retirement accounts, business valuations, recent tax returns, and a full list of debts, and attaching that schedule as an exhibit.
Is It Unconscionable?
Even with full disclosure and voluntary signing, a court can refuse to enforce a prenup that is so one-sided it would be fundamentally unfair to enforce. The standard is measured at the time the agreement was signed, though a dramatic change in circumstances can also come into play. A prenup that leaves one spouse with virtually nothing while the other keeps everything is the textbook example. Another common scenario: both spouses waive alimony, but during the marriage one becomes disabled and unable to work. What seemed fair at signing is now unconscionable given the changed reality.
Did Each Spouse Have Their Own Lawyer?
Most states do not strictly require that each party hire their own attorney, but the absence of independent counsel is a red flag for any judge reviewing the agreement. If one spouse had a lawyer draft the prenup and the other signed it without any legal advice, the court may question whether that person understood what they were giving up. When a party chooses to proceed without a lawyer, a written waiver confirming they had the opportunity and declined is standard practice, and courts look for it.
Signing Requirements
The Uniform Premarital Agreement Act requires only that the agreement be in writing and signed by both parties. Notarization and witnesses are not required by the uniform act, though many attorneys recommend notarization because it makes the agreement harder to challenge later. Some states do require witnesses, and a few have additional procedural rules, so execution requirements depend on where you live.
Timing matters more than most people realize. An agreement signed the week of the ceremony, even if technically voluntary, invites a challenge. Starting several months out gives both parties time to review drafts, consult their own attorneys, negotiate changes, and sign without deadline pressure — which is also what makes each individual clause more likely to hold up if the marriage ever ends.