Imagine the following scenario. You’re already married, life is humming along, and you feel secure knowing you never signed a prenup. Then, life unfolds. One spouse starts a business. The other inherits some property. Finances shift, careers evolve, children arrive, and suddenly, you’re both looking at the reality that “what’s mine is yours” might need a few more guardrails. That’s where postnuptial agreements come in and where skipping one can quietly put you at serious legal risk.
Most people have heard of prenups. Far fewer realize postnups exist, or that they can be just as important, sometimes even more so, because they address changes that occur after the wedding. And unlike prenups, which often carry an unfair stigma, postnups are about thoughtful planning rather than mistrust. But without one? You could be unintentionally leaving assets, inheritances, and even your future income vulnerable.
But why would I need a postnup? And, what are the requirements for a valid postnup? Continue reading to learn the answers to your questions and to discover more about postnuptial agreements.
What is a postnuptial agreement, and how is it different from a prenup?
A postnuptial agreement (or “postmarital agreement,” “marital agreement,” or “postnup”) is essentially a prenup’s younger sibling. It’s drafted and signed after you’re already married. Just like a prenup, it outlines how property, debts, and sometimes spousal support will be handled if the marriage ends in divorce or death. The key distinction is timing: while a prenup is signed before the marriage, a postnup is signed during the marriage.
Unlike prenups, postnups are typically treated differently by state law, and not all states approach them the same way. Some, like California, recognize postnups but impose heightened duties of loyalty and disclosure between spouses (California Family Code §721). Others, like Ohio, only recently began allowing them. Ohio changed its law in 2023 to permit postnups for the first time (Ohio Rev. Code Ann. §3103.06). And some states, like New Jersey, remain cautious and generally enforce postnups only when they are made in the context of reconciliation during marital breakdown. There are still a handful of states that do not enforce postnups. Currently, those include Iowa, Louisiana, and Nebraska, to name a few. That’s why knowing your state’s stance on postnups is crucial. Choosing not to create a postnup—especially in a state where they are enforceable—means leaving major financial issues up to default divorce laws, which may not reflect your intentions.
Risk #1: Default property division rules may surprise you
Without a postnup, your property division in a divorce is determined entirely by your state’s default rules. In community property states like Texas or Arizona, that means anything acquired or earned during the marriage is presumed to be part of the marital estate and generally split 50/50 in a divorce. This includes salary, savings, and even businesses started after the wedding.
In equitable distribution states like New York or Illinois, courts divide property based on what is “fair,” which doesn’t always mean equally. Judges look at factors like length of the marriage, contributions of each spouse, and future earning capacity. (N.Y. Dom. Rel. Law §236(B)(5)). The problem? “Fair” is subjective. Without a postnup that clearly defines what you both think is fair, you’re leaving that decision in the hands of a judge. That can lead to outcomes neither of you anticipated, like splitting a business you built solo or sharing future royalties from intellectual property you created solo.
Risk #2: Separate property can accidentally become marital
Many couples assume that property owned before marriage, like a home, investments, or an inheritance, automatically stays separate. In reality, separate property can lose its status through commingling or contributions from marital funds. For example, if you deposit inherited money into a joint account or use marital funds to improve a marital property, this could change the classification of your asset. Courts may treat that once-separate asset as marital and subject to division in a divorce. A notable example is the 2013 South Carolina case Wilburn v. Wilburn, where commingling turned separate funds into marital property (Wilburn v. Wilburn (2013)).
A postnup can proactively clarify what remains separate, even if the lines have started to blur. Without it, you risk losing control over assets you always intended to keep separate. This topic is especially important in second marriages where children from prior relationships are often involved.
Risk #3: Spousal support (alimony) defaults can be expensive
Another often-overlooked issue in divorce is spousal support (i.e. “alimony” or “maintenance.”) Without a prenup or postnup, courts apply state-specific guidelines, which can differ dramatically. For instance, Texas is famously conservative, capping spousal maintenance at the lesser of $5,000 per month or 20% of the paying spouse’s gross income, and only in limited circumstances (Tex. Fam. Code §8.055). In contrast, Massachusetts courts have broad discretion to award significant alimony based on the length of marriage and lifestyle established during it (Mass. Gen. Laws ch. 208, § 53).
A postnup can give you both clarity and control by waiving, limiting, or pre-defining the terms of spousal support. Without it, you’re at the mercy of statutory formulas and a judge’s interpretation of fairness, which can lead to costly and unpredictable results.
Risk #4: Business interests can be put at risk
If you or your spouse start or grow a business after marriage, a divorce without a postnup can throw that company into chaos. Courts may treat part, or all, of a business, even one operated by a single spouse, as marital property subject to division. That means that courts can award the other spouse a share, can force buyouts, valuations, or even the sale of the business. Starting and running a business without a postnup puts your business and your business partners in a very vulnerable situation.
A postnup can protect business interests by clarifying what portion of the company is separate, how any increase in value will be treated, and whether income from the business counts as marital property. Without that, you risk entangling your company in protracted litigation. Discerning who owns what portion of a valuable business can become central to divorce property battles, and can break your future business dreams and your bank account.
Risk #5: Estate planning becomes messy without one
Postnups not only discuss what happens to your property in a divorce, they also clarify what happens at death. Without one, state intestacy laws or elective share rules kick in, often granting the surviving spouse a significant share of the estate even if the deceased spouse wanted more to go to children from a prior relationship or other family members. For example, in Florida, a surviving spouse is entitled to 30% of the elective estate regardless of what a will says (Fla. Stat. §732.201).
This can undermine your estate plan, especially in blended families, where you may want to provide for children from a prior relationship or other loved ones. A postnup can waive elective share rights, define what each spouse should receive, and ensure your wishes are honored without conflict or costly litigation.
Procedural pitfalls: Requirements for a valid postnup
Even if you and your spouse agree on postnuptial terms, the agreement won’t help you unless it’s legally enforceable. Courts can and do strike down postnups that fail to meet procedural requirements. While the specific rules vary by state, most require:
- Full and fair financial disclosure
- Voluntary and informed signatures
- Fairness at the time of execution and enforcement
- Proper legal execution (including notarization and witnesses, where required)
State laws differ significantly on the details. Regarding fairness, states like Massachusetts apply the “two‑look doctrine,” checking fairness both when signed and at divorce. When it comes to execution, states have very firm and very different rules regarding witnesses, notarization, and special acknowledgments. New York, for example, has a requirement that a postnup be acknowledged with the same formalities as a deed.
That’s why working with a knowledgeable family law attorney in your state is essential. Don’t rely on generic templates that overlook your jurisdiction’s nuances. The procedural fine print matters. Skipping steps can make your postnup completely unenforceable just when you need it most.
Why this matters now more than ever
Postnups aren’t just for celebrities or the ultra-wealthy. They’re for any couple whose financial life looks different from what it did on their wedding day. Maybe you’ve launched a startup. Maybe a parent passed away and left an inheritance. Perhaps one spouse decided to leave their career to stay home and raise the children. These are real‑life triggers for couples everywhere, and they’re exactly the moments when a postnup can save you from future conflict.
The legal landscape is also evolving. States like Ohio are newly recognizing postnups. Others, like Minnesota, are tightening procedural rules for marital agreements across the board. And high‑profile cases, from trust disputes in Massachusetts to acknowledgment failures in New York, keep reminding us how unforgiving courts can be when agreements miss technical steps.
Final thoughts on the legal risks of not having a postnup
Skipping a postnup risks leaving your financial future up to chance and to default state laws that may not reflect your intentions. A well‑crafted postnup, tailored to your state’s rules, can prevent messy disputes, protect family businesses, preserve inheritances, and give you both clarity about what’s fair. If your marriage has evolved with new careers, new kids, or new assets, it might be time to evolve your financial plan, too.
A postnup isn’t planning for divorce—it’s planning for your future. It’s a legal tool that helps married couples protect what matters most, reduce uncertainty, and strengthen financial transparency. If your marriage has changed, your planning should, too.
Katherine (Kathy) Bakes is the founder and managing attorney of Bakes Law LLC. Her eleven years of practice involves all aspects of family law, including the formation of prenuptial and postnuptial agreements, divorce and legal separations, child custody, child support, and visitation agreements, spousal support and financial settlements. Kathy also engages in the practice of estate planning including the formation of wills, revocable and irrevocable trusts, durable powers of attorney, health care proxies, HIPAA authorizations and living wills. Kathy is a member of both the Connecticut and Massachusetts state bars after receiving her Juris Doctorate degree from New England Law | Boston. Kathy lives in Southport, CT with her husband and toddler. Outside the office, Kathy enjoys playing the piano and teaches music education to students of all ages.
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