Postnuptial Agreements in Divorce: Legal Validity and Limitations

Postnuptial agreements are contracts executed by spouses after marriage that govern how assets, debts, and support obligations will be divided if the marriage ends in divorce or legal separation. Unlike prenuptial agreements and divorce instruments drafted before the wedding, postnuptial agreements carry distinct enforceability questions because both parties are already bound by the legal duties of marriage when they sign. Courts across the United States apply heightened scrutiny to these agreements, and state law governs their validity in the absence of controlling federal statute. Understanding the scope, mechanics, and limits of postnuptial agreements is essential for grasping how divorce settlement agreements are ultimately shaped.

Definition and scope

A postnuptial agreement — sometimes called a "post-marital agreement" or "marital agreement" — is a written contract between two legally married spouses that specifies property rights, spousal support terms, and related financial arrangements in the event of divorce, separation, or death. The agreement takes effect while the marriage is ongoing but is designed to govern dissolution proceedings if they occur.

The legal framework for postnuptial agreements derives entirely from state law. No single federal statute regulates their formation or enforcement. The Uniform Law Commission published the Uniform Premarital and Marital Agreements Act (UPMAA) in 2012, offering states a model statute that expressly covers both premarital and marital agreements. As of 2023, states including Colorado, North Dakota, and Nebraska had adopted UPMAA or equivalent frameworks, though the majority of states continue to apply common-law contract doctrine supplemented by their own statutes.

The scope of a postnuptial agreement can include:

1. Division of marital and separate property — specifying which assets remain separate and which become marital upon dissolution
2. Spousal support or alimony terms — setting, capping, or waiving spousal support and alimony obligations
3. Debt allocation — assigning responsibility for existing and future debts
4. Business ownership interests — protecting a spouse's ownership stake in a business subject to valuation in divorce
5. Inheritance and estate provisions — though state probate law may override certain terms

Postnuptial agreements cannot govern child custody or child support. Courts retain independent authority over the best interests of the child standard, and any contractual attempt to predetermine custody outcomes or waive child support laws and guidelines is unenforceable as a matter of public policy.

How it works

Formation of a postnuptial agreement follows a process analogous to contract formation but with marriage-specific requirements layered on top. Courts in most states assess four primary factors when determining enforceability:

1. Voluntariness — Both spouses must execute the agreement free from duress, coercion, or undue influence. Because the marital relationship creates inherent power dynamics, courts apply stricter scrutiny to voluntariness than in ordinary commercial contracts.
2. Full financial disclosure — Each party must disclose all material assets, liabilities, and income. The UPMAA standard requires that a party either received fair and reasonable disclosure or voluntarily waived disclosure in writing after consulting independent counsel.
3. Substantive fairness — A number of states apply a "second look" doctrine at the time of enforcement: even if the agreement was fair when signed, a court may refuse to enforce terms that are unconscionable at the time of divorce. California, for example, applies this standard under California Family Code § 721, which imposes fiduciary duties between spouses that govern all marital agreements.
4. Written and signed formality — Oral postnuptial agreements are not enforceable. The agreement must be in writing and signed by both parties, with independent legal representation strongly recommended and required in some jurisdictions.

The timeline moves in two phases. First, during marriage, the agreement is drafted, disclosed, and executed. Second, at divorce, the agreement is submitted to the court as part of the dissolution process. The court reviews the agreement against the enforceability standards applicable in that state before incorporating its terms into the divorce decree enforcement framework.

Common scenarios

Postnuptial agreements arise in predictable factual patterns:

Post-infidelity reconciliation — Spouses negotiating reconciliation after an affair sometimes execute postnuptial agreements as a condition of continuing the marriage. Courts have split on whether these agreements are enforceable, with some treating the threat of divorce as inherently coercive.

Business acquisition during marriage — A spouse who founds or acquires a business after marriage may seek a postnuptial agreement to classify the business as separate property, reducing exposure in high-asset divorce legal considerations. Without such an agreement, business appreciation may be subject to equitable distribution or community property rules depending on the state.

Inheritance receipt — When one spouse receives a substantial inheritance, a postnuptial agreement can memorialize the parties' intent to treat those funds as separate property, providing clarity in jurisdictions where commingling would otherwise convert inheritance into marital property. This intersects with separate vs. marital property divorce doctrine.

Debt protection — A spouse who undertakes significant personal or business debt may use a postnuptial agreement to shield the other spouse from liability under divorce debt division rules.

Contrasting prenuptial and postnuptial agreements

Decision boundaries

Courts draw firm lines around what postnuptial agreements can and cannot accomplish.

Enforceable provisions:
- Division of real property and financial accounts
- Waiver or limitation of alimony, subject to state-specific unconscionability review
- Classification of separate versus marital property
- Allocation of specific debts

Unenforceable provisions:
- Any term that predetermines child custody or purports to waive child support
- Provisions that incentivize divorce (courts in multiple states have struck terms that effectively reward one spouse financially for filing)
- Clauses that violate public policy, such as those encouraging illegal conduct or penalizing a spouse for religious practice
- Terms executed under demonstrable duress — courts in states following no-fault vs. fault divorce frameworks remain sensitive to coercion evidence

The enforceability of spousal support waivers occupies contested ground. In California, under Family Code § 1612(c), a premarital waiver of spousal support is enforceable only if the waiving party was represented by independent counsel at signing — a standard many courts apply by analogy to postnuptial waivers. The federal vs. state divorce law structure means there is no national floor for these protections; a waiver valid in Texas may be unenforceable in New York.

Jurisdictional recognition presents a further complication. A postnuptial agreement executed in a community property state may be interpreted differently if the couple later divorces in an equitable distribution state. The divorce jurisdiction requirements applicable at the time of filing determine which state's law governs interpretation, and choice-of-law clauses within the agreement may or may not be honored depending on local precedent.

References

• Uniform Law Commission — Uniform Premarital and Marital Agreements Act (2012)
• California Family Code § 721 — Fiduciary Duties Between Spouses
• California Family Code § 1612 — Premarital and Marital Agreements, Spousal Support
• Cornell Law School Legal Information Institute — Postnuptial Agreement
• Uniform Law Commission — Summary of UPMAA Enactments by State