A prenup in a marriage, short for prenuptial agreement, is a contract two people sign before the wedding that spells out how their property, debts, and finances will be handled during the marriage and if it ends. It replaces the default divorce rules your state would otherwise apply with a set of rules you and your partner wrote yourselves. Most couples finalize the document weeks or months before the ceremony, after each person has disclosed their finances in full and negotiated the terms with their own attorney.
The agreement is binding. A judge will enforce it in a divorce as long as it was signed properly, both people knew what they were giving up, and the terms aren’t grossly unfair. That’s the whole point: you decide in advance, when things are calm, rather than leaving the outcome to a courtroom later.
What a Prenup Covers
The core job of a prenup is drawing a line between what belongs to each person individually and what the couple shares. Separate property usually means assets one person owned before the wedding, such as a house, a brokerage account, or savings. The agreement labels these so they stay off the table if the marriage ends. Marital property generally covers income earned and assets acquired during the marriage, and the prenup can change how those get divided too.
Debts get the same treatment. If one partner carries student loans or credit card balances into the marriage, the agreement can keep those obligations with the person who incurred them. Without that language, a divorcing spouse in some states could end up responsible for debts they never knew about.
Inheritances and gifts from family members are commonly designated as separate property to keep them within a specific family line. Business interests, including ownership stakes or the future growth of a company, are often ring-fenced so that a divorce doesn’t force a sale or operational disruption.
Spousal Support
One of the most consequential things a prenup can do is set the terms for spousal support. Couples can waive alimony entirely, cap the amount and duration of payments, or build in adjustments tied to the length of the marriage. A court will still review these provisions for fairness. If enforcing the alimony terms as written would leave one spouse destitute while the other walks away wealthy, a judge can modify or discard them. Some states will not enforce a spousal support waiver at all unless the person giving up that right had their own attorney when they signed.
Cryptocurrency and Digital Assets
Digital assets like Bitcoin and Ethereum need the same treatment as any other property, with extra complications. Values swing wildly, ownership is controlled by private keys rather than account titles, and hiding holdings in a crypto wallet is easier than hiding a bank account. A good prenup identifies each cryptocurrency by type and quantity, lists the wallet addresses where it’s stored, and includes a plan for how volatile assets will be valued if the marriage ends. Classifying crypto acquired before the wedding as separate property and spelling out how coins purchased during the marriage will be treated prevents ambiguity that could sink the whole agreement later.
What a Prenup Cannot Do
Some terms will not be enforced no matter what both parties agreed to.
Child custody and child support are off-limits. Courts have exclusive authority over children’s welfare, and judges determine custody and support based on the child’s best interests at the time of a split. Parents cannot bargain away their children’s rights in a contract signed before those children exist.
Lifestyle and infidelity clauses rarely survive either. Couples sometimes try to add penalties for cheating, requirements about household responsibilities, or other personal behavior rules. Courts overwhelmingly refuse to enforce them. Judges don’t want the job of monitoring conduct inside a marriage, and in no-fault divorce states, marital misconduct generally can’t influence property division anyway. Including an aggressive lifestyle clause doesn’t just waste paper; in some cases, it can lead a court to question the fairness of the entire agreement and throw the whole thing out.
Any term that violates public policy or requires illegal conduct is void on its face. Provisions designed to create a financial incentive to divorce are vulnerable too, and an agreement that’s grossly one-sided when signed can be declared unconscionable and refused outright.
Retirement and Social Security Benefits
Federal law overrides your prenup when it comes to certain retirement benefits, no matter what the agreement says. Under ERISA, the federal law governing most employer-sponsored retirement plans, a spouse has an automatic right to survivor benefits from the other spouse’s 401(k) or pension. A prenuptial agreement cannot waive those rights because, by definition, neither person is a “spouse” yet when they sign it. The statute requires that the waiver come from the plan participant’s spouse in writing, witnessed by a notary or plan representative, and submitted during the plan’s election period. The workaround is to include the intended waiver in the prenup and then confirm it in a postnuptial agreement signed after the wedding, when both people are legally spouses.
Social Security benefits are even more firmly off-limits. Spousal and survivor benefits under Social Security are controlled entirely by federal law and cannot be waived, modified, or bargained away in any private contract.
What Makes a Prenup Valid
A prenup that doesn’t meet your state’s validity requirements is just an expensive piece of paper. At least 26 states and the District of Columbia have adopted some version of the Uniform Premarital Agreement Act, which provides a baseline framework, but the specific rules vary. A few requirements are nearly universal:
- The agreement must be in writing and signed by both parties. Oral prenups are not enforceable anywhere.
- Both parties must sign voluntarily. Pressure, threats, or coercion will void the agreement, and a prenup presented for the first time the night before the wedding is a textbook red flag for duress.
- Both parties must give a fair and reasonable accounting of their assets, debts, and income before signing. Hiding a bank account or understating the value of a business can get the entire agreement thrown out.
Each person should have their own attorney during negotiations. Separate lawyers demonstrate that both parties received independent advice about how the contract affects their rights. Some states treat the absence of independent counsel as a factor weighing against enforceability, and in a few jurisdictions, provisions waiving spousal support are flatly unenforceable unless the person giving up that right was represented. If one party chooses to proceed without a lawyer, some states require a written waiver executed as a separate document, along with a waiting period after being advised to seek counsel. California, for example, requires at least seven days between receiving the final draft and signing.
Timing matters for a related reason. Courts scrutinize when the prenup was signed relative to the wedding. An agreement signed months in advance looks voluntary. One signed the morning of the ceremony, with caterers setting up in the next room, looks coerced. Starting the process at least several months out gives both sides time to negotiate without anyone feeling rushed.
Execution is formal. Both parties sign in front of a notary public, who verifies their identities, and some states also require witnesses. Electronic signatures work in some states under the Uniform Electronic Transactions Act but not others, because some jurisdictions carved out exceptions for family law documents. If there’s any doubt, sign with ink on paper. Keep originals in a secure location like a fireproof safe or a safe deposit box, with complete copies held by both spouses and their attorneys.
Keeping Separate Property Separate After the Wedding
Signing the prenup is only half the battle. Separate property designated in the agreement can lose its protected status through a process called transmutation, which happens when separate assets get mixed with marital funds to the point where they’re impossible to tell apart. The most common cause is commingling: depositing an inheritance into a joint checking account, using premarital savings to buy a house titled in both names, or running business income through a shared account.
Once assets are commingled, a court may treat them as marital property regardless of what the prenup says. Preventing this requires keeping separate property in separate accounts, maintaining clear records of where assets came from and how they were used, and avoiding changes to titles or deeds that blur ownership lines. The prenup creates the legal framework. Disciplined record-keeping is what makes it hold up.
What a Prenup Costs
The total cost generally ranges from about $1,000 to $10,000, with complexity driving the price. A straightforward agreement between two people with modest assets and no business interests lands at the lower end. Couples with multiple properties, business valuations, trust structures, or international assets will be closer to the top of that range or beyond it. Each spouse needs their own attorney, so the total cost is typically double whatever one lawyer charges. Business owners should also budget for a professional valuation, which is a separate expense from the legal drafting.