Prenup vs. Postnup: Differences, Costs, and Which One You Need

By Aaron Thomas, Esq. · Updated November 11, 2026

A prenup and a postnup do the same job: they replace your state’s default marital property rules with terms you choose. The difference is timing. A prenup is signed before the wedding and a postnup after, and in some states that timing brings stricter review and extra signing steps. In 2026, a prenup or postnup typically costs between $600 and $10,000 or more per couple, depending on how the agreement is created.

At Prenups.com, a prenup is a flat $3,500, or $5,000 to include negotiations with your partner’s attorney.

At Prenups.com, a postnup is a flat $4,500, or $6,500 to include negotiations with your spouse’s attorney.

Key Takeaways

• A prenup is signed before the wedding; a postnup is signed after. Both can classify property, income, and debt, and both can set terms for a divorce.
• Legally, the two documents are equal in power and reach. The real difference is timing, and timing affects leverage.
• Some states review postnups more strictly. Florida, for example, presumes concealment when a marital agreement is unfair or unreasonable, and that presumption is rebutted by full, frank disclosure or the challenger’s general and approximate knowledge of the other spouse’s finances.
• Some states add requirements for postnups that prenups do not face, such as acknowledgment before a certifying officer in North Carolina or consideration beyond the marriage in Tennessee.
• In 2026, either agreement typically costs $600 to $10,000 or more per couple. A prenup is the better choice when it is available; a postnup is far better than no agreement at all.

Prenup vs. Postnup: The Short Answer

There are only two contracts that let a couple replace their state’s one-size-fits-all marital rules with their own: a prenuptial agreement and a postnuptial agreement. Each can say what stays separate, what is shared, how income earned during the marriage is treated, who is responsible for which debts, and what happens to all of it if the marriage ends.

By default, income earned during the marriage is marital property, or community property in community property states, unless an agreement classifies it differently. That default is the reason either document exists. The only question is when you sign it.

Timing Is Leverage

Before the wedding, both partners hold the same bargaining chip: the choice to marry or not. Once the marriage is official, that leverage changes. One spouse may have stepped back from a career, moved for the other’s job, or folded savings into a shared home. A postnup is negotiated between people whose finances are already intertwined.

That is why a prenup is the better choice when it is available. Drawing the lines before the wedding creates a clean starting point while both partners stand on equal footing. It is also why plenty of postnups start life as prenups. A couple who cannot finish before the ceremony can finish afterward, which is what happens when you didn’t finish the prenup before the wedding and convert the draft into a postnup.

Couples are also marrying later, with more to sort out. In 2025, the median age at first marriage was 30.8 for men and 28.4 for women, according to the U.S. Census Bureau. Many arrive with retirement accounts, homes, and businesses already in place, and some only realize after the wedding that those assets need written terms.

Where the Law Treats Postnups Differently

Postnups follow different rules from prenups in most states, and the differences cluster in three areas.

The first is scrutiny. Because the marriage already exists, some states review postnups more closely than prenups. In Casto v. Casto (1987), the Florida Supreme Court held that a marital agreement may be set aside for fraud, deceit, duress, coercion, misrepresentation, or overreaching, or if it is unfair or unreasonable, which raises a presumption of concealment that can be rebutted by full, frank disclosure or the challenger’s general and approximate knowledge of the other spouse’s finances.

The second is consideration. Some states require a postnup to be supported by something of value beyond the marriage itself, because the marriage already happened. In Bratton v. Bratton (2004), the Tennessee Supreme Court held that postnuptial agreements are not against public policy but require adequate consideration and knowing, voluntary entry, and it invalidated the agreement before it for lack of consideration.

The third is execution. North Carolina’s premarital agreement statute requires only a signed writing, but N.C. Gen. Stat. § 52-10 requires a contract between spouses that affects real property to be in writing and acknowledged by both spouses before a certifying officer. New York applies the same formalities to both: under DRL § 236(B)(3), a prenup or postnup must be in writing, subscribed, and acknowledged in the manner required to record a deed.

None of this makes a postnup weak. It means a postnup has to be built for the state whose law governs it, with complete disclosure, independent counsel for each spouse, and the right signing steps. For the state-by-state picture, see the full guide to postnuptial agreements.

What Each One Costs

The market range is the same for both: $600 to $10,000 or more per couple. A $600 template sits at the bottom, software-drafted agreements with attorney review start at $2,000, and traditional hourly attorneys typically run $2,500 to $10,000.

Prenups.com charges a flat fee for each, with no hourly billing. The postnup fee is higher because a postnup is built for the stricter review many states apply, starting with a full, current financial record from both spouses.

Which One You Need

If you are not married yet, you need a prenup, and the earlier you start, the better. If the wedding is close and the agreement is not finished, keep going: an unfinished prenup can become a postnup without losing its purpose. If you are already married, a postnup is the tool, and it can be signed at any stage of the marriage in the states that enforce them. The common question of whether you can get a prenup after you’re married is really a question about a postnup.

“A prenup and a postnup are equal in legal power. The difference is when you sign, and after the wedding that difference shows up as stricter review in some states, so the record behind a postnup has to be complete from the first draft,” says Aaron Thomas, Esq., founder of Prenups.com.

Every agreement starts with a consultation about what each of you owns and what you want the agreement to do. The full flat-fee pricing is published. Schedule a consultation.

Frequently Asked Questions

Sources

• Casto v. Casto, 508 So. 2d 330 (Fla. 1987) (grounds for setting aside a marital agreement; presumption of concealment)
• Bratton v. Bratton, 136 S.W.3d 595 (Tenn. 2004) (postnuptial agreements require adequate consideration)
• N.C. Gen. Stat. § 52-10 (contracts between husband and wife; acknowledgment): https://www.ncleg.gov/EnactedLegislation/Statutes/HTML/BySection/Chapter_52/GS_52-10.html
• N.Y. Domestic Relations Law § 236(B)(3) (agreements made before or during the marriage; acknowledgment)
• U.S. Census Bureau, “Census Bureau Releases New Estimates on America’s Families and Living Arrangements” (Dec. 2, 2025) (median age at first marriage): https://www.census.gov/newsroom/press-releases/2025/families-and-living-arrangements.html