Can You Get a Prenup After Marriage? Postnuptial Agreements Explained

Short answer: yes, you can get the equivalent of a prenup after you are already married. It just has a different name. An agreement signed before the wedding is a prenuptial (or premarital) agreement; an agreement signed after you are legally married is a postnuptial (or marital) agreement. A true "prenup" must, by definition, be signed before you marry, because the word means pre-nuptial. But the goal most people have in mind, putting financial expectations in writing and deciding in advance how assets and support would be handled, is still available to married couples through a postnuptial agreement.

This page is written for readers who are already married and searching for whether it is too late. It is not too late. Below we explain the difference, what makes a postnup hold up, and where the rules get stricter, because this is governed by state law and the details genuinely vary from state to state.

Do you need to be married to get a prenup?

It is the opposite. A prenuptial agreement requires that you are not yet married when you sign it. The agreement is made "in contemplation of marriage" and only takes legal effect once the marriage actually happens. If the wedding never occurs, the prenup is generally void.

So the common questions all point to the same answer:

• "Does a prenup need to be done before marriage?" Yes. A prenup is by definition signed before the wedding.
• "Does a prenup need to be signed before marriage?" Yes. If you sign after the ceremony, it is not a prenup at all, it is a postnup.
• "Do you need to be married to get a prenup?" No, you need to be about to marry. You need to be married to get a postnup.
• "Can I have a prenup after marriage?" Not a prenup, but yes, you can have its married-couple counterpart: a postnuptial agreement.

What is a postnuptial agreement?

A postnuptial agreement is a written contract between spouses, signed after they are legally married, that sets out how they would divide property, debts, and (in many states) spousal support if they later divorce or one spouse dies. It can cover much of the same ground a prenup would: separating what each person owns, protecting a business or inheritance, clarifying responsibility for debt, or simply replacing the default rules your state would otherwise apply.

Couples reach for a postnup for a range of reasons, for example after one spouse receives an inheritance or starts a business, when finances have changed significantly, when a couple reconciling after a rough patch wants clearer ground rules, or simply because they meant to do a prenup and ran out of time before the wedding.

Prenup vs. postnup: the key difference

The mechanical difference is timing: prenup before the wedding, postnup after. But there is an important legal difference too. Before marriage, an engaged couple are still at arm's length and free to walk away. Once married, spouses owe each other heightened duties of good faith and fair dealing. Because of that relationship, many courts scrutinize postnuptial agreements more carefully than prenuptial ones, and a handful of states have historically been skeptical of, or have refused to enforce, certain postnups. This is one of the biggest reasons the "after marriage" version is not simply a late prenup, and why getting it done correctly matters.

Is a postnup enforceable?

In most states a properly made postnuptial agreement is enforceable, but enforceability depends entirely on your state's law and on how the agreement was made. There is no single federal statute governing prenups or postnups; this is state contract and family law. A few patterns show up across states:

• It must be in writing and signed. Oral marital agreements are generally not enforceable.
• It must be voluntary. An agreement signed under duress, coercion, or threat (for example, "sign this or I file for divorce tomorrow") can be thrown out.
• There should be fair financial disclosure. Each spouse should know, at least in general terms, what the other owns and owes. Note an important nuance drawn from the Uniform Premarital Agreement Act framework that many states follow: inadequate disclosure is not a standalone reason to void an agreement on its own. It is part of the broader "unconscionability" analysis, and a spouse who signs a clear, express written waiver of further disclosure generally cannot later attack the agreement just for lack of disclosure.
• It cannot be unconscionable. Courts can refuse to enforce terms that are grossly unfair, especially if they would leave one spouse destitute.
• It generally cannot bind a court on child custody or child support. Those decisions are made in the child's best interests at the time, and spouses cannot contract them away in advance.

A note on the governing law: the older Uniform Premarital Agreement Act (UPAA), adopted in many states, covers premarital agreements only and does not by its terms govern postnups. The newer Uniform Premarital and Marital Agreements Act (UPMAA, 2012) covers both, but it has been adopted in only a small number of states. In states that have adopted neither for marital agreements, postnups are judged under that state's case law and general contract principles. The bottom line: do not assume the rules are the same everywhere, and check what your state requires.

What a postnup can and cannot do

Commonly allowed

• Classifying property as separate vs. marital, including future earnings and appreciation.
• Protecting a business, professional practice, or expected inheritance.
• Allocating responsibility for existing and future debt.
• Setting or waiving spousal support / alimony (allowed in many but not all states, and subject to fairness review).
• Spelling out what happens to property at death, which can coordinate with estate planning.

Usually not allowed

• Predetermining child custody or child support in a way that binds the court.
• Terms that are illegal, or "lifestyle" clauses (chores, weight, frequency of visits to in-laws) that courts typically will not enforce.
• Anything procured by fraud, duress, or hidden assets.

What you can do

1. Decide what you actually want to accomplish. Protect a business? Wall off an inheritance? Clarify debt? Knowing the goal shapes the agreement and keeps it focused and fair.
2. Both gather full financial information. List assets, debts, income, and accounts for both spouses. Honest, documented disclosure is one of the strongest defenses against a later challenge.
3. Get separate, independent legal advice. Each spouse having their own lawyer is the single best way to show the agreement was voluntary and understood. Postnups with only one lawyer (or none) are far easier to attack later.
4. Put everything in writing and don't rush the signing. Give each person real time to read, ask questions, and negotiate. Avoid signing on the eve of a threatened divorce, which looks like duress.
5. Follow your state's formalities. Some states require notarization or witnesses, and some treat spousal-support waivers specially. Confirm what your state demands so the document is valid where you live.
6. Keep it fair and keep a signed copy. An agreement that is balanced and that neither leaves a spouse destitute nor hides assets is far more likely to be enforced. Store originals safely.

Time-sensitive and state-specific cautions

• Timing matters for fairness. Signing a postnup while a divorce is already threatened or filed can make it look coerced. If you want an agreement, the calmer the moment, the stronger it is.
• State law controls and varies a lot. Whether spousal support can be waived, how closely postnups are scrutinized, and what formalities are required differ by state. A clause that is routine in one state may be unenforceable in another.
• If you and your spouse are separating to different states, which state's law and courts apply can become contested. That is a question to raise with a local attorney early.

Bottom line

You cannot get a literal "prenup" after you are married, because a prenup is defined as a pre-wedding agreement. But you can absolutely get its married-couple version, a postnuptial agreement, and for many already-married couples that is exactly the right tool. Because postnups are governed by state law and are often scrutinized more closely than prenups, the safest path is full disclosure, independent lawyers for each spouse, no pressure, and careful attention to your own state's rules. Our per-state pages cover the specific requirements where you live.

This article is general information, not legal advice. Postnuptial agreement rules vary by state; consult a licensed attorney in your state about your situation.