Wisconsin: Prenuptial Agreement Requirements

Requirements one by one

Wisconsin uses a marital property agreement statute

Wisconsin calls a prenup a marital property agreement. Section 766.58 governs agreements made before or during marriage and lets prospective spouses contract about property, support, death transfers, and related financial matters.

The agreement must be a document signed by both prospective spouses. No additional consideration is needed, and signing does not make the prenup effective: under § 766.58(5), it becomes effective only when the parties marry.

Notarization and witnesses are not statutory validity steps

Section 766.58 states no notary, acknowledgment, witness, attestation, or oath requirement. It also makes recording optional: married or prospective spouses may record the agreement with a county register of deeds, but recording is not a condition of validity between them.

Disclosure has a notice alternative, not a waiver form

The spouse resisting enforcement may prove both that the spouse did not receive fair and reasonable disclosure of the other's property or financial obligations and that the spouse lacked notice of them. Because § 766.58(6)(c) joins those failures with “and,” adequate notice can defeat this disclosure-based defense.

Wisconsin does not supply a separate-writing waiver of financial disclosure. A clause saying “disclosure waived” is not the statutory substitute for information or notice.

Counsel and timing are not bright-line conditions

No Wisconsin statute fixes a final-draft review period or a minimum number of days before the wedding. Section 766.58 also does not require separate lawyers. It goes further: shared counsel, or representation of only one party, does not by itself make the agreement unconscionable or otherwise unenforceable.

The agreement still must be voluntary and must pass the applicable fairness reviews. The statute's point is that counsel imbalance alone does not decide the case.

Formation and divorce use distinct fairness reviews

Section 766.58(6) makes an agreement unenforceable if the challenger proves it was unconscionable when made, was not signed voluntarily, or failed the disclosure-and-notice test. The court decides unconscionability as a matter of law.

Property terms face an additional divorce-stage rule. Section 767.61(3)(L) presumes a written property agreement equitable and binding, but not when its terms are inequitable to either spouse. Button explains that fair disclosure, free and voluntary entry, and substantively fair property terms are the three requirements. Even terms fair at signing may become unfair at divorce when significantly changed circumstances make the agreement depart from the parties' reasonable expectations.

A support waiver has two statutory safety valves

A marital property agreement may modify or eliminate spousal support. During marriage, however, the change may not leave a spouse with less than necessary and adequate support after all sources are considered.

At divorce or death, a court may order the other spouse or estate to provide enough support to prevent public-assistance eligibility caused by the agreement. This is a targeted statutory override, not a general invitation to rewrite every support waiver because circumstances changed.

Child and prohibited terms remain outside private control

Section 766.58(2) bars an agreement from adversely affecting a child's support right. Custody and physical placement also remain for the court: § 767.41(5)(am) requires consideration of all facts relevant to the child's best interest.

Other property terms may not violate public policy or a statute imposing a criminal penalty. A financial agreement cannot privately authorize what Wisconsin law forbids.

Amendment or revocation requires another full agreement

Section 766.58(4) allows amendment or revocation only through a later marital property agreement. The change must itself qualify as such an agreement and meet the statute's signed-document and enforceability requirements.

What trips people up

Signing is not the effective date. A premarital agreement takes effect only if and when the parties marry.

Disclosure “waiver” and notice are different. Wisconsin's statute uses fair disclosure or notice; it does not create a uniform-act-style written waiver of further disclosure.

There are two fairness moments for property terms. Section 766.58 examines formation, while § 767.61(3)(L) and Button preserve a divorce-time equity review for significant changes outside reasonable expectations.

Common questions

Does a Wisconsin prenup need to be notarized?

Not under § 766.58's general validity rules. This page does not assess separate instruments used to carry out an agreement term.

Does shared counsel automatically invalidate the agreement?

No. Section 766.58(8) says shared counsel does not by itself invalidate the agreement. Voluntariness and fairness still must be established.

Can a prenup eliminate all maintenance?

It may contain a waiver, but the waiver cannot leave a spouse inadequately supported during marriage, and a court may order enough support at divorce or death to avoid public-assistance eligibility caused by the agreement.

Can the agreement lock in a future custody schedule?

No. The court must decide legal custody and physical placement from the child's best interests when the issue arises.

Statutes and sources

• Wis. Stat. § 766.58. Current official marital-property-agreement rules for the signed document, consideration, marriage trigger, permissible subjects, formation defenses, counsel, support, recording, and later change. Official statute (accessed July 28, 2026).
• Wis. Stat. § 767.61(3)(L). Presumption and divorce-time equity rule for written property agreements. Official statute (accessed July 28, 2026).
• Wis. Stat. § 767.41(5)(am). Best-interest rule for custody and physical placement. Official statute (accessed July 28, 2026).
• Button v. Button, 131 Wis. 2d 84 (1986), quoted and applied in Hartford v. Hartford, No. 2012AP1911 (Wis. Ct. App. Aug. 15, 2013). Three-part equity test and significant-changed-circumstances review. Official Wisconsin Court System opinion (accessed July 28, 2026).