Postnuptial Agreements

Some of the most consequential marital contracts are signed after the wedding. Maybe there was no time — or no appetite — for a prenup. Maybe a business took off, an inheritance arrived, one of you stepped back from a career, or the marriage hit a hard stretch and you both want to stay in it with the money questions settled. Florida law lets married spouses do all of this by contract. But the rules are different from prenuptial agreements — older, stricter, and far less forgiving of shortcuts — and a postnup drafted like a prenup is a postnup waiting to fail.

What a postnuptial agreement is — and when couples reach for one

A postnuptial agreement is a contract between spouses, made during the marriage, that settles financial rights — property division, spousal support, estate claims — by agreement rather than leaving them to Florida's default statutes. In practice, couples come to us for a postnup in a handful of recurring situations:

• The prenup that never happened. The wedding arrived faster than the paperwork, or the conversation felt too hard at the time. Marriage does not close the window; it just changes the rules for the document.
• Circumstances changed. A company was founded or took off, a windfall or inheritance arrived, equity vested, one spouse guaranteed significant business debt. The financial picture the marriage started with no longer exists, and the default rules now produce outcomes neither spouse intended.
• One spouse is stepping back from a career. Before a partner leaves the workforce to raise children or support a move, a postnup can guarantee what that sacrifice will — and will not — cost them.
• Reconciliation. After infidelity or a serious rupture, some couples choose to continue the marriage with the financial consequences of a future split agreed in advance. Removing the money fight from the table is sometimes exactly what makes staying possible.
• Estate-plan coordination in blended families. Spouses in second marriages often use a postnup to waive elective-share and homestead claims against each other's estates so that children from prior marriages inherit as intended.
• Updating an existing prenup. Under § 61.079(6), Florida Statutes, a premarital agreement can be amended, revoked, or abandoned only by a signed written agreement — which is, by definition, a postnuptial agreement. Agreements drafted before Florida's 2023 alimony reform, which still speak in terms of permanent alimony, are prime candidates for review.

Different law applies — and it is stricter

Here is the distinction that surprises people, including some lawyers. Florida's premarital agreement statute, § 61.079, governs only agreements "between prospective spouses made in contemplation of marriage." Once you are married, it does not apply to you. Postnuptial agreements are governed by common-law contract principles and by the Florida Supreme Court's framework in Casto v. Casto (Fla. 1987) — which was itself a postnuptial agreement case.

Under Casto, a spouse challenging a postnup has two independent avenues:

• Procedural attack. The agreement was the product of fraud, deceit, duress, coercion, misrepresentation, or overreaching. This mirrors the prenup rule.
• Substantive attack — with a burden shift. If the agreement makes an unfair or unreasonable provision for the challenging spouse given the parties' circumstances, a presumption arises that assets were concealed or unknown — and the burden shifts to the spouse defending the agreement to prove either full, frank disclosure of the marital finances, or that the challenger had general and approximate knowledge of them anyway.

That burden shift is the critical difference. A premarital agreement challenger must carry the burden all the way through; a postnup proponent can be forced to affirmatively justify the deal years later. The saving grace is the same in both worlds: a bad bargain, standing alone, is not grounds for relief. As the court put it in Casto, the fact that one party "apparently made a bad bargain" is not enough to vacate an agreement. Lopsided survives. Concealed does not.

Why the extra scrutiny? Because engaged people negotiate at something like arm's length, while married people are in a confidential relationship — the law treats spouses as fiduciaries to one another, not as counterparties. The price of contracting with someone the law says you must deal with in utmost good faith is that the good faith gets examined.

Disclosure: the non-negotiable core

In a prenuptial agreement, § 61.079 permits the parties to waive financial disclosure in a signed writing, and a valid waiver forecloses a later unconscionability attack. Postnups have no such statutory escape hatch. Boilerplate reciting that "each party waives disclosure" does not defeat the Casto presumption — if the agreement is unreasonable on its face, the defending spouse must still prove disclosure or knowledge.

The estate statute makes the same point even more bluntly. Under § 732.702(2), Florida Statutes, a waiver of spousal estate rights signed before marriage requires no disclosure at all — but for a waiver signed after marriage, "each spouse shall make a fair disclosure to the other" of their estate. Post-marriage, disclosure is not best practice. It is a statutory element.

So we treat disclosure as the foundation of every postnuptial agreement: sworn schedules of assets, liabilities, and income for both spouses, with account statements attached as exhibits and independent valuations where a business or unusual asset is involved. It is more work than a recital. It is also the difference between a contract and a controversy.

What a postnup can cover — and what it cannot

The permissible subject matter largely tracks prenuptial agreements:

• Property rights — which assets are separate, which are marital, and how existing and future property (including a business and its future appreciation) will be characterized and divided at dissolution or death.
• Spousal support — establishing, capping, or waiving alimony by contract rather than leaving it to § 61.08's discretionary factors.
• Estate rights — waivers of the elective share, homestead, intestate share, exempt property, and family allowance, executed with the two subscribing witnesses § 732.702 requires and supported by the fair disclosure it mandates.
• Debts — allocating responsibility for student loans, business obligations, and guarantees so one spouse's exposure stays theirs.
• Life insurance and support floors — securing obligations so the promises in the agreement are actually collectible.

The limits are equally familiar, and they do not soften after the wedding:

• Children's rights are untouchable. Child support belongs to the child, and parental responsibility and time-sharing are decided by the court under the best-interests standard when the question actually arises. A postnup cannot pre-decide either.
• Temporary support and fees cannot be waived. The rule of Belcher v. Belcher (Fla. 1972) — that support obligations during an intact marriage, including temporary alimony, suit money, and temporary attorney's fees in a pending dissolution, cannot be contracted away — applies to marital agreements generally. Florida courts have voided such waivers in postnups just as in prenups.
• Public policy still polices conduct clauses. Provisions purporting to penalize infidelity or regulate personal behavior remain of doubtful enforceability, in a postnup no less than a prenup.

One technical note worth knowing: consideration. A prenup is supported by the marriage itself; in a postnup the marriage has already happened, so the agreement is supported by the parties' mutual promises and releases — and for estate-rights waivers, § 732.702(3) provides that no consideration is required at all. This is a drafting detail with teeth, and one reason recycled prenup forms make poor postnups.

Postnup versus prenup: the practical differences

• Governing law. Prenups: § 61.079, Florida Statutes. Postnups: common law and Casto.
• Disclosure. Prenups: waivable in a signed writing. Postnups: effectively mandatory — and statutorily mandatory for estate waivers.
• Burden of proof. Prenups: stays on the challenger. Postnups: an unreasonable deal shifts the burden to the spouse defending it.
• Pressure points. Prenups fail over wedding-eve timing. Postnups fail over concealed finances and overreaching within a relationship of trust.
• What survives in both. Freedom of contract on property and alimony; the children carve-out; the Belcher temporary-support rule; the two-witness requirement for estate waivers; and the principle that a merely one-sided deal, honestly made, is enforceable.

If you are reading this before the wedding: sign the prenup. The statutory framework is more predictable and the disclosure rules more flexible. But if you are already married, none of that is a reason to wait — Casto-tested postnups are enforced by Florida courts every year. The difference is not whether the document can hold. It is how carefully it must be built.

A word about agreements signed once divorce is underway

Timing changes the legal species. An agreement negotiated after a dissolution petition has been filed — with the discovery tools of litigation available to both sides — is a marital settlement agreement, not a postnup, and under Macar v. Macar (Fla. 2001) it is not subject to Casto's heightened scrutiny. Spouses in active litigation are treated as adversaries dealing at arm's length. So a "postnup" signed on the courthouse steps buys none of the fiduciary-relationship protections, and a settlement agreement attacked later faces a much steeper climb. Which document you are signing, and when, is itself a strategic decision — one worth making with counsel rather than discovering in a motion years later.

The process we follow

• An honest opening conversation. A postnup raised by ambush does damage a document cannot fix. We help clients frame the why — estate planning, the business, the reconciliation — before anyone frames terms.
• Independent counsel for each spouse. Given the fiduciary relationship and the burden-shifting rule, separate representation matters even more here than in prenups. One lawyer cannot represent both of you.
• Disclosure done properly. Sworn financial schedules from both spouses, statements attached, valuations where warranted. This is the load-bearing wall of the agreement.
• Negotiation with a record. Exchanged drafts and documented give-and-take are the best evidence, years later, that nobody was overreached.
• Execution with two witnesses and a notary — so property terms hold in the divorce court and estate waivers hold in the probate court.
• Scheduled reviews. Major life events — a sale, a windfall, a move, a new child, a change in the law like the 2023 alimony reform — are triggers to revisit the agreement in writing, because informal understandings amend nothing.

What a postnuptial agreement costs

In the Central Florida market, postnuptial agreements generally run in the same range as negotiated prenups — commonly $2,000 to $5,000 in combined fees where both spouses are represented — and sometimes more, because the mandatory disclosure work is heavier: the marital estate must be documented as it exists today, not merely as two premarital snapshots. Business interests, professional practices, and substantial estates add valuation costs. As with everything the firm does, fees are quoted individually after a consultation. The comparison that matters is not postnup versus prenup; it is contract versus litigation, where a single contested issue can consume the cost of the entire agreement many times over.

How Mack Law approaches postnuptial agreements

A postnuptial agreement is financial architecture inside a fiduciary relationship — the drafting has to be right on the law and right on the numbers. Michael Mackhanlall's pre-law background in business, securities, and investment banking shapes how these agreements are built: around real balance sheets, real valuations, and the specific ways Florida courts have taken agreements apart. The firm drafts postnups, reviews and negotiates agreements presented by a spouse's counsel, restructures outdated prenups, and — when marriages do end — enforces sound agreements and challenges unsound ones. We draft every document as if opposing counsel will someday read it looking for the exit. That is the standard a postnup has to meet, because someday, one might.

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This page describes Florida law in general terms as of its last update and is not legal advice about any specific situation. Statutes cited include §§ 61.079, 61.08, and 732.702, Florida Statutes. Court decisions are summarized; outcomes always depend on specific facts.