Postnuptial Agreement: Can You Get a Prenup After Marriage?

Yes — you can get a prenup-equivalent after marriage. It's called a postnuptial agreement (or "postnup"). Most US states recognize postnuptial agreements and most courts enforce them, though the rules are stricter than for prenups signed before the wedding. Postnuptial agreement cost typically runs $1,500–$8,500 — similar to a prenup, sometimes slightly higher.

This page explains what a postnup is, when couples sign one, what it costs, and which procedural rules tend to decide whether a court will enforce it later. This isn't legal advice. If you're considering a postnup, talk to a family law attorney licensed in your state.

What a postnuptial agreement is

A postnuptial agreement is a contract between spouses, signed after they're married, that sets out what happens to property and income if the marriage ends. It can cover the same ground as a prenup: which assets are separate, which are marital, who keeps what, and whether spousal support applies.

Two things make postnups legally distinct from prenups:

• The parties are already married, so they owe each other a fiduciary duty — a higher standard of honesty and fairness than parties to an arms-length contract.
• Most state courts apply stricter scrutiny when reviewing a postnup, especially around financial disclosure and voluntariness.

When couples actually sign postnups

In practice, most postnups follow a triggering event. Common ones:

• One spouse starts a business after the wedding and wants to define how that business gets treated if the marriage ends.
• An inheritance is coming and the couple wants to clarify it stays separate property.
• The couple skipped a prenup before the wedding and now wants to put one in place.
• One spouse received a large gift or windfall during the marriage.
• The couple had a serious financial disagreement and wants the resolution on paper.
• One spouse plans to leave their career to care for children, and both want to address the financial impact.

You don't need a triggering event. Some couples sign a postnup simply because they didn't get around to a prenup before the wedding and want the same protection going forward.

How much does a postnuptial agreement cost?

For most couples, a postnuptial agreement runs $1,500 to $7,500 in attorney fees. Complex estates — multiple businesses, real estate in different states, expected inheritances — can run $10,000 or more.

A postnup often costs slightly more than the equivalent prenup, for two reasons:

1. Both spouses need their own attorney. Most states treat joint representation as a strong reason to invalidate a postnup later. Two attorneys, two sets of fees.
2. Disclosure is more involved. The longer you've been married, the more co-mingled the finances. Documenting what's separate vs. marital takes attorney hours that a pre-marriage couple often doesn't need.

Online services like LegalZoom and HelloPrenup also offer postnup options at the ~$600 price point with attorney review. That's reasonable for the simplest situations — both spouses on W-2 income, no business, no kids from prior relationships, no major separate property. Anything more complex calls for a real attorney in your state.

Are postnuptial agreements legally binding? What makes them enforceable

Every state has its own framework, but the recurring requirements look like this:

• In writing and signed by both spouses. Oral agreements between spouses about future property are unenforceable across the board.
• Full and fair financial disclosure. Each spouse must show the other a complete picture of their assets, debts, and income. Hiding a business interest or a brokerage account is the fastest path to invalidation.
• Voluntary execution. Neither spouse can be coerced. Signing while one spouse is threatening divorce is a red flag courts take seriously.
• Independent counsel for both spouses. Some states require it; in the rest, courts treat its absence as strong evidence of unfairness.
• Not unconscionable. An agreement that leaves one spouse with nothing while the other keeps everything will be struck down in most jurisdictions, regardless of what the document says.

The single most common reason courts refuse to enforce a postnup is inadequate disclosure — one spouse didn't know the real value of what they were giving up. That's why each spouse's attorney typically requires the other side to produce statements, tax returns, and a sworn schedule of assets before the document gets signed.

Prenup vs. postnup, in one paragraph

A prenup is signed before the wedding and is governed by contract-law principles plus your state's premarital agreement statute. A postnup is signed during the marriage and is reviewed under your state's contract law plus the fiduciary duty spouses owe each other. The substance is largely the same; the scrutiny isn't. If you can sign a prenup before the wedding, do that. If you can't or didn't, a postnup is a real and usable option. For a deeper comparison, see prenup vs. postnup.

When a postnup probably isn't enough

A postnup is the wrong tool when:

• One spouse is already threatening or pursuing divorce. The duress argument writes itself.
• One spouse can't or won't provide complete financial disclosure.
• The couple wants to decide child custody or child support in advance. State courts decide both based on the best interests of the child at the time of divorce — a contract can't change that.
• One spouse is signing without independent legal advice.

In any of those situations, the postnup is likely to be set aside if the marriage later ends, leaving the couple with the same default state-law outcome they would have had without an agreement.

How to get a postnuptial agreement: next steps

If you're thinking about a postnup, the practical sequence is straightforward:

1. Each spouse retains their own family law attorney.
2. Both spouses produce complete financial disclosure — assets, debts, income.
3. The attorneys negotiate the substance: separate vs. marital property, support, what happens to specific assets if the marriage ends.
4. Each spouse reviews with their own attorney before signing.
5. The agreement is signed, often with notarization, and stored with each spouse's attorney.

To find a family law attorney who handles postnuptial agreements in your state, start with our state-by-state attorney directory or get a calibrated cost estimate from our state cost calculator.