A prenuptial agreement can cover almost any financial arrangement between two future spouses: who keeps which assets, who answers for which debts, whether spousal support is limited or waived, how a business is treated, and how inheritance rights are handled. What a prenup cannot do is decide child custody or support, waive federally governed benefits like Social Security, dictate personal behavior during the marriage, or impose terms a court later finds grossly unfair. The line between the two categories is sharper than most couples expect, and a provision that crosses it can jeopardize the rest of the agreement.
Property and Who Owns What
Defining property is the most common reason couples sign a prenup. Without one, state law decides how assets get divided in a divorce, and those default rules may not match what either spouse would choose. A prenup lets you override the defaults by classifying specific assets as separate property that belongs to one spouse alone.
Separate property typically covers anything you owned before the marriage, plus inheritances and gifts received during it. The agreement can list exactly which assets qualify: real estate, investment accounts, savings, collectibles, or anything else of value. It can also address what happens when separate property appreciates during the marriage, a question that catches many couples off guard. Jointly acquired assets can be redefined too. Income earned during the marriage, retirement contributions, and purchases made with shared funds can all be classified however the couple agrees, rather than following state defaults.
Debt Allocation
Debt protection is where prenups deliver some of their most practical value, especially when one spouse enters the marriage with significant liabilities. A prenup can state that pre-existing debts like student loans, credit card balances, or car loans remain the sole responsibility of the spouse who incurred them. Without that language, divorce courts in some states may treat certain pre-marital debts as a shared obligation.
The agreement can also set rules for debts taken on during the marriage. If one spouse runs up credit card charges for personal expenses, the prenup can assign responsibility for that balance. Specificity matters here. A vague statement that “debts remain separate” is weaker than language identifying categories of debt and who answers for them. A prenup can also shield one spouse’s personal assets from the other’s creditors if that spouse defaults on a loan or faces a lawsuit.
Spousal Support
Prenups can set the terms for spousal support, commonly called alimony, including the monthly amount, how long payments last, and what events end them. Couples can agree to limit support, tie it to the length of the marriage, or waive it entirely.
Courts respect these arrangements up to a point, and the limit is fairness. If enforcing a waiver would leave one spouse destitute, especially after a long marriage in which that spouse sacrificed career opportunities, a court can override the prenup. The legal term is “unconscionable,” meaning so one-sided that no reasonable person would have agreed to it with full information. A significant, unforeseen change in circumstances, like a serious illness or disability that didn’t exist at signing, can also lead a court to modify or disregard the support terms.
Business Interests
For anyone who owns a business or plans to start one, a prenup is one of the most effective tools for keeping that business out of a divorce. The agreement can classify the business as separate property, establish a method for valuing it, and specify how ownership interests would be handled if the marriage ends. Without that structure, a divorcing spouse may have a claim to a portion of the business, potentially forcing a sale or buyout at the worst possible time.
A well-drafted prenup can also separate business income from the business itself, distinguishing between the company’s value and the salary or distributions the owner-spouse takes from it. That distinction can prevent fights over whether business profits earned during the marriage count as marital property.
Inheritance and Estate Rights
Most states give a surviving spouse an automatic right to a portion of the deceased spouse’s estate, often called an “elective share,” regardless of what the will says. A prenup can waive that right, which is especially important in second marriages where each spouse wants to preserve assets for children from a prior relationship.
The agreement can also coordinate with trusts, beneficiary designations, and other estate planning tools so assets pass according to the couple’s wishes rather than default inheritance laws. If you have a family business, inherited property, or assets you want to leave to specific people, the prenup should address those intentions explicitly.
Retirement Accounts: An Important Federal Limit
Prenups can address how 401(k)s, IRAs, and pensions get divided in a divorce, but there is a federal rule that trips people up. ERISA, the federal law governing most employer-sponsored retirement plans, prevents a prenup from waiving survivor benefits.
The reason is technical. Under federal law, only a “spouse” can waive the right to survivor benefits on an ERISA-qualified plan, and the waiver must be in writing, witnessed by a plan representative or notary, and name an alternative beneficiary. When you sign a prenup, you are not yet married, which means you are not yet a “spouse” under the statute. The waiver simply does not count.1Office of the Law Revision Counsel. 29 USC 1055 – Requirement of Joint and Survivor Annuity and Preretirement Survivor Annuity
The fix is straightforward. Include the retirement benefit waiver in the prenup as a statement of intent, then sign a formal postnuptial waiver after the wedding that complies with ERISA’s requirements. Skipping that second step is one of the most common and costly prenup mistakes, because the prenup language alone has no legal effect on the retirement plan no matter how clearly it’s written.
Other Enforceable Clauses
Prenups can go beyond property and support. Several other kinds of provisions are widely recognized:
- Attorney fees. The agreement can specify who pays legal costs if the prenup is challenged or if the couple divorces.
- Choice of law. Couples who might relocate can designate which state’s laws govern the agreement, though courts sometimes override this if the chosen state has no real connection to the couple.
- Dispute resolution. A clause requiring mediation or arbitration before litigation can save both spouses significant time and money.
- Sunset clauses. The prenup can include an expiration date, automatically voiding the agreement after a set number of years of marriage.
- Pet ownership. An increasing number of couples include provisions about who keeps a pet after divorce, along with arrangements for veterinary expenses and care responsibilities. A growing number of states now consider a pet’s best interests in custody disputes, making these clauses more relevant than they once were.
What a Prenup Cannot Include
Child Custody and Child Support
No prenup can determine child custody, visitation schedules, or child support amounts. Courts decide these issues based on the child’s best interests at the time of divorce, using the circumstances that actually exist then, not predictions made years earlier. Any provision attempting to set custody or support terms will be struck down, and in some states, including such provisions can call the entire agreement’s enforceability into question.
Provisions That Encourage Divorce
Clauses that create a financial incentive to divorce are unenforceable as a matter of public policy. The classic example is a provision that awards one spouse a large payout only if they file for divorce within a certain timeframe, or a penalty for remaining married. Courts view marriage as a relationship the law should support, not one that contracts should undermine.
Unconscionable Terms
A prenup that is overwhelmingly one-sided can be thrown out as unconscionable. Courts evaluate this at the time of enforcement, not just at signing. An agreement that seemed reasonable when both spouses were working professionals can become unconscionable if one spouse later gave up a career to raise children and the prenup leaves them with nothing. A judge, not a jury, decides this question, and the spouse challenging the agreement bears the burden of proof.
Illegal Terms and Lifestyle Clauses
Anything requiring illegal conduct is automatically void. Less obviously, courts also reject personal lifestyle clauses, such as provisions dictating a spouse’s weight, appearance, frequency of visits to in-laws, household chores, or religious practices. These fall outside the scope of a financial contract, and courts have no interest in monitoring or enforcing them. Loading a prenup with lifestyle provisions can also undermine its credibility and invite closer scrutiny of the whole agreement.
Infidelity Clauses
Infidelity clauses occupy a gray area. These provisions typically impose a financial penalty, such as a larger property share or increased support, if one spouse cheats. Whether they hold up depends heavily on where you live. States with purely no-fault divorce systems tend to reject them because they function as punishment for marital misconduct, which contradicts the no-fault framework. States that still recognize fault-based grounds for divorce, particularly adultery, are more likely to enforce them. If an infidelity clause matters to you, confirm your state’s position before relying on it.
Social Security and Other Federal Benefits
A prenup cannot waive a spouse’s right to Social Security benefits based on the other spouse’s earnings record. Social Security eligibility and calculations are governed entirely by federal law, and no private agreement can alter them. The same principle applies to other federally administered benefits: if the right comes from a federal program, a prenup cannot eliminate it.
What Makes a Prenup Hold Up
Content is only half the equation. Even a reasonable agreement can be thrown out if the process was flawed. The Uniform Premarital and Marital Agreements Act, adopted in some form by a majority of states, lays out the core requirements, though individual states may add their own.
Written, Signed, and Voluntary
A prenup must be a written document signed by both parties. Verbal agreements do not count, no matter how detailed. No additional consideration beyond the marriage itself is required, meaning neither spouse needs to “pay” for the other’s agreement to sign.2Uniform Law Commission. Uniform Premarital and Marital Agreements Act
Both spouses must sign voluntarily. If either person was pressured, threatened, or coerced, the agreement is unenforceable. A prenup delivered the night before the ceremony, with the implicit message that the wedding is off unless it’s signed, is the textbook scenario courts use to find duress.
Full Financial Disclosure
Both parties must provide a reasonably accurate picture of their finances before signing. That means disclosing assets, debts, income, and financial obligations. The disclosure does not need to be down to the penny, but it must be honest and complete enough that both spouses can make an informed decision about the terms.2Uniform Law Commission. Uniform Premarital and Marital Agreements Act
Hidden assets are one of the fastest ways to get a prenup invalidated. If a court later discovers that one spouse concealed a bank account, undervalued a business, or omitted significant debts, the entire agreement can be thrown out, not just the provisions tied to the hidden assets. A spouse can waive the right to full disclosure, but that waiver must be explicit, in writing, and ideally made after consulting a lawyer.
Access to Independent Legal Counsel
Not every state requires each spouse to have their own attorney, but the absence of independent legal representation is one of the most common grounds for challenging a prenup. Under the model act, each party must have reasonable time to decide whether to hire a lawyer and, if they choose to do so, reasonable time to find one, get advice, and consider it. If one spouse has a lawyer and the other does not, and the unrepresented spouse lacked the means to retain one, courts will look closely at whether that spouse truly understood what they were giving up.2Uniform Law Commission. Uniform Premarital and Marital Agreements Act
Separate attorneys for each spouse during drafting is the single best investment in making a prenup difficult to overturn. The cost of two lawyers up front is a fraction of what it costs to litigate enforceability years later.
Timing
Start early. A prenup signed weeks or months before the wedding is far stronger than one signed days before. When a prenup appears last-minute, courts worry that one spouse felt trapped, with deposits paid, invitations sent, and family arriving. That pressure can be enough to establish duress even without an explicit threat. There is no universal rule for how far in advance is “enough,” but the more time both spouses had to review, negotiate, and consult lawyers, the harder the agreement is to challenge.