South Dakota Prenuptial Agreement Laws: UPAA Rules and Enforcement

Prenuptial agreements are enforceable in South Dakota under the Uniform Premarital Agreement Act, SDCL 25-2-16 to 25-2-25. The agreement must be in writing and signed by both parties (SDCL 25-2-17), and SDCL 25-2-21 sets out when a court will refuse to enforce it.

Information last verified on 2026-10-08. This article has not been reviewed by a licensed lawyer.

Jurisdiction scope: This article covers premarital agreements under South Dakota's Uniform Premarital Agreement Act, SDCL 25-2-16 to 25-2-25, with notes on SDCL 25-2-13 and 25-4-44. It does not cover South Dakota case law on prenups, custody terms, which agreements the act governs by signing date, or other states' law. For property division at divorce, see South Dakota divorce laws.

Are prenups enforceable in South Dakota?

Yes. South Dakota adopted the Uniform Premarital Agreement Act in 1989 (SL 1989, ch 216). SDCL 25-2-25 provides: "Sections 25-2-16 to 25-2-25, inclusive, may be cited as the Uniform Premarital Agreement Act." This page does not cover which agreements the act governs by the date they were signed.

What a South Dakota prenup needs to be valid

The formal requirements are short. SDCL 25-2-17 provides: "A premarital agreement shall be in writing and signed by both parties. It is enforceable without consideration." South Dakota's statute of frauds, SDCL 53-8-2(2), separately requires a writing for "an agreement made upon consideration of marriage, other than a mutual promise to marry."

SDCL 25-2-19 adds: "A premarital agreement becomes effective upon marriage."

Sections 25-2-16 to 25-2-25 do not require notarization, witnesses, or a waiting period between signing and the wedding. The statute also does not require each party to have a lawyer. A lawyer licensed in South Dakota can draft or review an agreement, but the act does not make that a condition of validity.

When a South Dakota court will not enforce a prenup

SDCL 25-2-21(a) puts the burden on the person resisting the agreement. It is not enforceable if that party proves either of two things.

1. It was not signed voluntarily. Under 25-2-21(a)(1), the agreement fails if "That party did not execute the agreement voluntarily."

2. It was unconscionable, and disclosure was lacking. Under 25-2-21(a)(2), the agreement fails if it "was unconscionable when it was executed and, before execution of the agreement, that party":

• "(i) Was not provided a fair and reasonable disclosure of the property or financial obligations of the other party;"
• "(ii) Did not voluntarily and expressly waive, in writing, any right to disclosure ... beyond the disclosure provided; and"
• "(iii) Did not have, or reasonably could not have had, an adequate knowledge of the property or financial obligations of the other party."

The second route is demanding. The agreement must have been unconscionable when signed, and all three disclosure conditions must be met; an unfair agreement alone is not enough under the statute.

Under 25-2-21(b), "An issue of unconscionability of a premarital agreement shall be decided by the court as a matter of law."

Spousal support and alimony waivers

Some versions of the Uniform Premarital Agreement Act include an extra subsection on agreements that modify or eliminate spousal support. South Dakota's 25-2-18 and 25-2-21 do not contain that subsection. This page does not cover how South Dakota courts treat alimony waivers in a prenup; a South Dakota lawyer can advise on a specific agreement. For alimony rules generally, see South Dakota alimony laws.

What a prenup cannot do: child support

SDCL 25-2-18(b) provides: "The right of a child to support may not be adversely affected by a premarital agreement." This page does not cover whether a prenup can address custody.

Inheritance rights

Under SDCL 29A-2-213(a), a spouse's right of election and rights to a homestead allowance, exempt property and family allowance "may be waived, wholly or partially, before or after marriage, by a written contract, agreement, or waiver signed by the surviving spouse." Under 29A-2-213(b), the waiver is not enforceable if the surviving spouse proves it was not executed voluntarily, or that it was unconscionable when executed and the same three disclosure conditions found in 25-2-21 were met.

Changing or revoking a prenup

SDCL 25-2-20 provides: "After marriage, a premarital agreement may be amended or revoked only by a written agreement signed by the parties. The amended agreement or the revocation is enforceable without consideration."

Time limits and void marriages

Limitations are paused during the marriage. SDCL 25-2-23 provides: "Any statute of limitations applicable to an action asserting a claim for relief under a premarital agreement is tolled during the marriage of the parties to the agreement. However, equitable defenses limiting the time for enforcement, including laches and estoppel, are available to either party."

If the marriage is void. Under SDCL 25-2-22, "If a marriage is determined to be void, an agreement that would otherwise have been a premarital agreement is enforceable only to the extent necessary to avoid an inequitable result."

Postnuptial agreements in South Dakota

This page does not cover a statute or case written specifically for postnuptial agreements. SDCL 25-2-13 provides that spouses cannot by contract alter their legal relations except as to property, and it allows a written agreement to an immediate separation that provides for support of either spouse and their children.

How South Dakota divides property without a prenup

South Dakota is not a community property state. Under SDCL 25-4-44, "When a divorce is granted, the courts may make an equitable division of the property belonging to either or both, whether the title to such property is in the name of the husband or the wife." See South Dakota divorce laws for how that division works.

Disclaimer: This article provides general legal information about premarital agreements under South Dakota law, SDCL 25-2-16 to 25-2-25, with notes on SDCL 25-2-13 and 25-4-44. It is not legal advice. The information was verified on 2026-10-08, and the law can change. For advice about a specific agreement, consult a lawyer licensed in South Dakota.

Related

• Prenuptial agreement laws in every state
• South Dakota divorce laws
• South Dakota alimony laws

Last updated: 2026-10-08.

Frequently Asked Questions

Does South Dakota follow the Uniform Premarital Agreement Act?

Yes. South Dakota enacted it in 1989, and it is codified at SDCL 25-2-16 to 25-2-25 (short title in 25-2-25).

Does a prenup need to be notarized in South Dakota?

SDCL 25-2-17 requires only that a premarital agreement be in writing and signed by both parties, and the act's sections do not add a notarization or witness requirement.

Do both parties need a lawyer for a South Dakota prenup?

The Uniform Premarital Agreement Act as enacted in South Dakota (SDCL 25-2-16 to 25-2-25) does not require independent counsel, though either party may choose to have a lawyer review the agreement.

How can a prenup be invalidated in South Dakota?

Under SDCL 25-2-21, the challenging party must prove the agreement was not signed voluntarily, or that it was unconscionable when signed and the party lacked fair disclosure, did not waive disclosure in writing, and had no adequate knowledge of the other's finances.

Can a South Dakota prenup limit child support?

No. SDCL 25-2-18(b) provides that the right of a child to support may not be adversely affected by a premarital agreement.

Can you change a prenup after marriage in South Dakota?

Yes, but only by a written agreement signed by both spouses, which is enforceable without consideration (SDCL 25-2-20).