Prenuptial and Postnuptial Agreements: What They Cover, When They Hold Up, and Common Myths

A prenuptial agreement (prenup) is a contract signed before marriage that specifies how assets and debts will be divided if the marriage ends in divorce. A postnuptial agreement (postnup) is the same thing, signed after the wedding. Both serve the same fundamental purpose: replacing the state's default rules for property division with terms the couple chose themselves. Without a prenup or postnup, divorce property division follows your state's laws — either community property (50/50 split of marital assets in 9 states) or equitable distribution (fair but not necessarily equal split in 41 states). These default rules may not match what you and your spouse would have agreed to. A prenup lets you decide in advance, when both parties are cooperative and thinking clearly, rather than fighting over it during the emotional chaos of divorce. Here is the thing most people get wrong: prenups are not just for wealthy people protecting their fortune. They are useful whenever there is an imbalance — one person has significantly more assets, one person owns a business, one person has student debt, one person is giving up a career to raise children, or one person expects a large inheritance. The agreement addresses that imbalance explicitly rather than leaving it to a judge's interpretation of fairness. Postnups are less common but increasingly used. They address situations that arise after marriage: one spouse starts a business, one receives an inheritance, or the couple wants to restructure their financial arrangement after a marital crisis. Some couples use postnups as an alternative to divorce — establishing financial boundaries while staying married.

Prenups and postnups can address almost any financial matter: division of property (separate and marital), debt allocation, spousal support (alimony) waivers or caps, business ownership protection, inheritance protection, and how specific assets (the house, retirement accounts, stock options) will be treated in divorce. Business protection is one of the most compelling reasons for a prenup. If one spouse owns a business before the marriage, or starts one during the marriage, the business's growth in value during the marriage could be considered a marital asset subject to division. A prenup can specify that the business remains separate property, or limit the other spouse's claim to a specified amount or percentage. What you cannot include: child custody and child support. Courts will not enforce any prenup provision that attempts to predetermine custody or limit child support, because these decisions must be made in the child's best interest at the time of divorce, not years earlier when circumstances were different. Any prenup clause about children is unenforceable and can undermine the credibility of the entire agreement. You also cannot include provisions that are unconscionable — meaning so one-sided that no reasonable person would agree to them. A prenup that leaves one spouse destitute while the other keeps millions will be scrutinized heavily. Courts are not obligated to enforce agreements that produce fundamentally unfair outcomes, even if both parties signed. Some states limit or prohibit waiving alimony in a prenup. Others allow it but may override the waiver if enforcement would leave one spouse on public assistance. Know your state's specific rules. DivorceIQ includes state-by-state guides to prenup enforceability. This content is for educational purposes only and does not constitute legal advice.

Courts evaluate enforceability based on both procedural fairness (how the agreement was created) and substantive fairness (what the agreement says). Failing on either dimension can get the agreement thrown out. Procedural requirements that most states share: both parties must have independent legal counsel (or at least the opportunity to consult one — having the same lawyer draft the agreement for both parties is a red flag). There must be full and fair financial disclosure — each party must provide a complete picture of their assets, income, and debts. The agreement must be in writing and signed voluntarily, without coercion or duress. And there must be adequate time between signing and the wedding — a prenup presented the night before the ceremony can be challenged as signed under duress. The timing issue is more important than people realize. Presenting a prenup two months before the wedding gives both parties time to consult attorneys, negotiate terms, and make an informed decision. Presenting it two weeks before the wedding — when invitations are sent, venues are booked, and the emotional and social pressure to proceed is enormous — creates a duress argument. Some courts have invalidated prenups signed within days of the wedding specifically on this basis. Substantive requirements: the terms must not be unconscionable at the time of enforcement (not just at signing). A prenup that was fair when signed may be unconscionable 20 years later if circumstances changed dramatically — one spouse became disabled, gave up a career to raise children, or the income disparity widened enormously. Courts in most states have the discretion to modify or void provisions that produce fundamentally unfair results given the circumstances at the time of divorce.

The most common mistake is hiding assets during disclosure. If one party discovers during divorce that the other failed to disclose a bank account, an investment, or the true value of a business, the entire agreement can be voided — not just the provision related to that asset. Courts treat non-disclosure as fraud, and fraud kills contracts. Second most common: one attorney drafting the agreement for both parties. Even if both spouses say they are fine with it, courts view this as a conflict of interest that undermines the voluntariness of the agreement. Each party should have their own attorney who reviews the agreement and advises their client independently. The cost of two attorneys ($3,000-8,000 total for a standard prenup) is trivial compared to the cost of an unenforceable agreement in a $500,000+ divorce. Third: including provisions about personal behavior. Clauses like the cheating spouse forfeits all assets or one spouse must maintain a certain weight or lifestyle are generally unenforceable. Courts view these as punitive provisions that have no place in a financial contract. Including them can also make the entire agreement look unreasonable to a judge. Fourth: failing to update the agreement. A prenup signed at age 28 with $50,000 in combined assets may not be appropriate at age 48 with $2 million in assets, three children, and one spouse who left a career to parent full-time. Couples should review and potentially update their agreement every 5-7 years or after major life changes (children, career changes, significant wealth accumulation). A postnup can update or replace a prenup to reflect current circumstances.