Can you get a prenup after marriage?

Short Answer

Yes—but after marriage, the agreement is a postnuptial agreement, not a prenuptial agreement. In California, spouses may enter one, but courts scrutinize it closely because spouses owe each other fiduciary duties and must provide fair, full financial disclosure.

California Requirements

A postnuptial agreement should generally:

• Be in writing and signed by both spouses;
• Include complete and accurate disclosure of assets, debts, income, and obligations;
• Be entered voluntarily, without coercion or undue influence;
• Provide terms that are not unconscionable;
• Avoid provisions that improperly restrict statutory rights or child-support obligations; and
• Ideally involve separate independent counsel for each spouse.

California’s premarital-agreement statute applies to agreements made before marriage and does not itself govern ordinary postnuptial agreements. Cal. Fam. Code §§ 1600–1617

Because spouses owe one another fiduciary duties, a postnuptial agreement may be challenged for nondisclosure, unfairness, or undue influence. Cal. Fam. Code §§ 721, 1100(e)

A postnuptial agreement should not be treated as a simple contract between unrelated parties; the marital fiduciary relationship creates heightened obligations.

California courts have recognized that marital-property agreements and transmutations must satisfy heightened formal and evidentiary requirements. In re Marriage of Benson, 36 Cal. 4th 1096, 1099–1100 (2005) [1]

Practical Point

A valid postnuptial agreement can address property characterization, debts, spousal support, and rights upon separation or death. It cannot predetermine child custody or waive a child’s right to support. Because enforceability is highly fact-specific, each spouse should use separate counsel and complete formal financial disclosures.