What Is a Postnuptial Agreement in Florida?

By Nadia Pazos, Family Law Attorney, Pazos Law Group · Updated October 14, 2026

Quick Answer

What is a postnuptial agreement in Florida? A Florida postnuptial agreement is a written contract signed by spouses after they are already married that sets out how property, debts, and spousal support will be handled if the marriage ends. Unlike a prenup, it is not governed by Fla. Stat. § 61.079 — that statute applies only to premarital agreements. Postnuptial agreements are enforced under Florida common law, and the controlling case is Casto v. Casto, 508 So. 2d 330 (Fla. 1987). A postnup cannot adversely affect a child’s right to support.

Pazos Law Group, a family law firm in Coral Gables serving Miami-Dade, Broward and Palm Beach counties, drafts and reviews postnuptial agreements, in English or Spanish: (305) 482-1262.

What a Florida Postnuptial Agreement Can Cover

Spouses have broad freedom to contract about their financial relationship. A well-drafted Florida postnup commonly addresses:

Classification of property — identifying what each spouse treats as separate and what is marital, which matters because § 61.075 equitable distribution otherwise decides it
A business or professional practice — particularly one started or grown during the marriage
Debt allocation — including student loans, business debt, and liabilities one spouse brought in
Spousal support — waiving, capping, or defining alimony rather than leaving it to § 61.08
The marital home — who keeps it, how equity is credited, and what happens to the mortgage
Inheritances and gifts — confirming they remain separate even if commingled
Estate rights — coordinating with wills, trusts, and elective share planning

What a Postnuptial Agreement Cannot Do

The limit is the same one that applies to prenups, and it is absolute: a postnuptial agreement cannot adversely affect a child’s right to support. That right belongs to the child, not to the parents. Florida courts will disregard any provision that waives, caps, or reduces child support, no matter how clearly both spouses agreed to it. Support is calculated under § 61.30 using the guidelines in effect at the time of the case.

Time-sharing and parental responsibility are likewise decided under § 61.13 according to the best interests of the child when the issue arises. Parents cannot bind a court in advance.

Is a Postnuptial Agreement Valid in Florida?

Yes. Florida recognizes postnuptial agreements between spouses. They are enforced under contract law and the standards in Casto v. Casto, 508 So. 2d 330 (Fla. 1987) rather than under § 61.079, which governs only premarital agreements. Under Casto, a spouse can challenge a marital agreement on either of two grounds:

Fraud, deceit, duress, coercion, misrepresentation, or overreaching. This looks at how the agreement came about — pressure, concealment, or one spouse taking unfair advantage of the other.
The agreement is unfair or unreasonable given the parties’ circumstances. If the challenging spouse establishes this, Florida law raises a presumption that assets were concealed, and the burden shifts to the spouse defending the agreement to show either that there was full and fair disclosure, or that the challenging spouse had a general knowledge of the marital property.

In practice, the agreements that hold up share four traits: a complete written disclosure exchanged before signing, independent counsel for each spouse, enough time between presentation and signature to show the decision was unhurried, and terms that leave the less-monied spouse in a position a court would not call unconscionable.

How Do You Get a Postnuptial Agreement, and Is It Filed With the Court?

Each spouse makes a full financial disclosure, the terms are negotiated, ideally with a separate lawyer for each spouse, and both sign the written agreement. It is a private contract: nothing is filed with the court or recorded, and it is produced only if it is later enforced or challenged. If it waives rights at death, such as the elective share or homestead, § 732.702(1) requires the waiving spouse to sign in the presence of two subscribing witnesses, and § 732.702(2) requires fair disclosure because it is signed after marriage.

Postnuptial vs. Prenuptial: What Actually Differs

Governing law. A prenup is governed by § 61.079. A postnup is governed by common law and Casto.
Consideration. A prenup is enforceable without separate consideration — the marriage itself supplies it. A postnup is an ordinary contract between married people, so it needs consideration; mutual waivers of rights typically supply it, which is one reason a one-sided postnup is riskier than a one-sided prenup.
Scrutiny of disclosure. Courts examine disclosure closely in both, but the existing marital relationship makes it a sharper issue in a postnup.
Timing pressure. A prenup carries the “signed days before the wedding” risk. A postnup has no deadline, which removes one of the most common voluntariness attacks.

Not married yet? See can you get a prenup after getting married in Florida? and our Florida prenuptial agreement attorney page.

Frequently Asked Questions

Can a postnuptial agreement waive alimony in Florida?

Spouses may address spousal support by contract rather than leaving it to § 61.08. Whether a particular waiver is enforced depends on how the agreement was made and whether it is unfair or unreasonable under Casto. A waiver that leaves one spouse destitute is far more vulnerable than one that provides a defined, negotiated amount.

Do we each need our own attorney?

Florida does not require it, but independent counsel for each spouse is the strongest evidence that signing was voluntary and informed, and it substantially reduces the risk of a later challenge. One attorney cannot ethically represent both spouses.

I received an inheritance during the marriage. Can a postnup keep it separate?

It usually starts out separate: assets “acquired separately by either party by noninterspousal gift, bequest, devise, or descent” are nonmarital (Fla. Stat. § 61.075(6)(b)2.). The risk is mixing it with marital money — a joint account, or a jointly titled home — which can make it hard to trace later. A postnuptial agreement can confirm that the inheritance, its income and anything bought with it stay separate; assets excluded “by valid written agreement of the parties” are nonmarital under § 61.075(6)(b)4.

Can we change or cancel a postnuptial agreement later?

Yes. Spouses may amend or revoke a postnuptial agreement by a later written agreement signed by both of them. Oral modifications are not reliable and should not be relied on.

Can a postnuptial agreement be an alternative to divorce?

Yes, for couples who want to stay married. Florida has no legal separation, so a postnup is often how spouses settle property, debt, and alimony terms while remaining married, for example to keep health coverage through one spouse’s employer. If the decision to divorce is already made, the document you need is a marital settlement agreement instead.

Primary Sources

Casto v. Casto, 508 So. 2d 330 (Fla. 1987) — the Florida Supreme Court standard for challenging a marital agreement.
Fla. Stat. § 61.075 — equitable distribution; nonmarital assets, including those excluded by valid written agreement.
Fla. Stat. § 732.702 — waiver of spousal rights; two witnesses, and fair disclosure for agreements signed after marriage.
Fla. Stat. § 61.079 — premarital agreements only (not postnups).

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