Prenuptial and postnuptial agreements carry a reputation for being unromantic, but for many couples in Campbell, they are simply a practical step toward a more secure future together. Whether you are planning a wedding or are already married and want to put financial expectations in writing, understanding what these agreements can and cannot legally contain under California law is the first step.

What Is the Difference Between a Prenup and a Postnup?

A prenup is signed before marriage; a postnup is signed after. California premarital agreements are primarily governed by Family Code sections 1600–1617. Postnuptial agreements are addressed separately under Family Code section 1620 and are evaluated in light of spouses’ fiduciary duties under section 721.

A prenuptial agreement generally becomes effective upon the parties’ marriage, subject to the agreement’s specific terms and legal enforceability. A postnuptial agreement is created after the wedding date and requires slightly different considerations around fairness and disclosure, since the legal relationship between spouses introduces fiduciary duties that did not exist before marriage.

Premarital agreements are enforceable under the California Premarital Agreement Act, Family Code sections 1600 through 1617. Postnuptial agreements are not simply prenups signed later; they are governed by section 1620, subject to fiduciary-duty principles under section 721, and receive heightened judicial scrutiny.

What Can Be Included in a Prenup or Postnup?

California law allows couples to address property rights, debt allocation, spousal support, and estate planning rights in a valid marital agreement, provided enforceability requirements regarding drafting, voluntariness, disclosure, and independent legal counsel are met.

California law gives couples significant flexibility when drafting these agreements. The following topics are generally permissible:

• Characterization of property: You can specify that certain assets, such as a business, real estate, or investments, remain separate property even if they grow in value during the marriage, provided the agreement properly addresses income, appreciation, tracing, management, reimbursement claims, and potential transmutation issues.
• Debt allocation: You can agree on which spouse is responsible for debts brought into the marriage or incurred during it.
• Spousal support (alimony): California Family Code section 1612 allows couples to limit, waive, or define the terms of spousal support, though a waiver or limitation generally requires representation by independent legal counsel to be enforceable, and courts may decline enforcement if the provision is unconscionable at the time of enforcement.
• Management of property: The agreement can define which spouse controls specific assets and how financial decisions are made.
• Inheritance and estate rights: Couples can address what happens to their property at death, including modifying or waiving rights the other spouse would otherwise have under California intestate succession laws, though agreements should be carefully coordinated with wills, trusts, and beneficiary designations to fully implement the estate plan.

These provisions enable couples to build a financial framework that reflects their actual circumstances, rather than relying entirely on California’s default community property rules.

What Cannot Be Included in a Prenup or Postnup?

California law restricts provisions attempting to predetermine child custody, waive child support, or encourage divorce, as courts retain ultimate authority over child welfare and public policy.

Even a carefully drafted agreement has firm legal limits. Under California law, the following cannot be enforced:

• Child custody and visitation: Courts determine these based on the best interests of the child at the time of divorce or separation, not on a contract signed years earlier. While parents may make nonbinding or temporary arrangements, courts retain authority to determine custody and visitation, and no agreement can override this standard.
• Child support: Under California child-support statutes, such as Family Code sections 3900 and 4001, child support rights belong to the child, and parents cannot prospectively waive or improperly limit legally required support.
• Provisions encouraging divorce: Any clause that improperly penalizes, rewards, or creates a financial incentive to terminate the marriage is considered contrary to public policy and will not be enforced.
• Unconscionable terms: If a court finds that an agreement was unconscionable under statutory standards at execution—or for spousal support, at enforcement—it may void the agreement or specific provisions within it.
• Illegal terms: No agreement can require illegal conduct, waive nonwaivable statutory rights, or violate public policy.

One nuance worth noting: a spousal support waiver is generally unenforceable under Family Code section 1612(c) unless the spouse whose support rights are limited or waived was represented by independent legal counsel at the time of signing. This is one reason why having separate attorneys review the agreement matters.

Procedural Requirements That Affect Enforceability

For a California prenup to be enforceable, it must be in writing, signed voluntarily, and supported by fair and reasonable financial disclosure, or a valid statutory waiver of disclosure where permitted.

Even a well-drafted agreement can fall apart if procedural rules are ignored. Under California Family Code section 1615, a prenuptial agreement is presumed involuntary if a party was not represented by independent counsel and did not have at least seven calendar days between the time the final agreement was first presented and the time it was signed.

Full and fair financial disclosure is equally critical. Both spouses must provide a fair and reasonable disclosure of property and financial obligations, or execute a valid statutory waiver. Materially concealing assets or misrepresenting financial details can constitute grounds for invalidating the agreement or specific provisions.

Postnuptial agreements carry additional scrutiny. Because spouses owe each other fiduciary duties under Family Code section 721, courts examine postnups closely for any signs of overreaching, undue influence, coercion, lack of disclosure, or unconscionability, and to determine whether each spouse had meaningful independent advice. Note that the statutory seven-day rule applies to prenups, not postnups.

Why Working With an Attorney Matters

An attorney ensures your agreement is drafted correctly, fully disclosed, and structured to hold up in court under California’s specific requirements.

A template downloaded from the internet does not account for California’s specific statutory requirements or the unique details of your financial picture. An agreement that skips required disclosures, rushes the signing process, or contains prohibited clauses may fail to satisfy statutory requirements or adequately address the couple’s circumstances when needed.

At Hepner & Pagan, we take a thoughtful, court-free approach to family law matters. Our philosophy centers on mediation, collaborative law, and out-of-court solutions that reduce stress and protect both parties. When we help couples draft prenuptial or postnuptial agreements, the goal is clarity and mutual understanding, not conflict.

We serve couples throughout Campbell, Los Gatos, and the greater Santa Clara County area. If you are ready to start the conversation, we encourage you to reach out to our team directly at 408-688-9153 or via our website to schedule a consultation.