A South Dakota prenuptial agreement is a written contract between two people who plan to marry, made in contemplation of marriage and effective only when the wedding takes place. South Dakota law calls it a premarital agreement. It sets out what each spouse owns, how property and debt are handled during the marriage, and what happens to both if the marriage ends.[1.1]
Is South Dakota a 50 50 divorce state? No, it follows equitable distribution, which is why couples use a prenup to fix their own terms in advance. The contract covers property, debt, life insurance, and estate planning, and it may not reduce a child's right to support.[1.3] It must be in writing and signed by both parties, and it is enforceable without consideration.[1.2]
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Courts and lawyers in this state also call the document a premarital agreement, an antenuptial agreement, or simply a prenup. The names mean the same thing, and Chapter 25-2 uses premarital agreement throughout. A couple who signs the same kind of contract after the wedding has a postnuptial agreement instead. For the rules that apply in every state, see our prenuptial agreement guide.
A South Dakota premarital agreement is an agreement between prospective spouses, made in contemplation of marriage and to be effective upon marriage. The definition limits the document to people who are not yet married, and it ties the force of the contract to the wedding rather than to the day it was signed.[1.1]
The agreement becomes effective upon marriage.[1.4] It is enforceable without consideration, so neither partner has to pay or transfer anything to the other to make it binding.[1.2]
Sections 25-2-16 through 25-2-25 of the South Dakota Codified Laws govern premarital agreements in this state. They set the form the contract must take and list the subjects a couple may settle in it. They also name the grounds on which a judge will refuse to enforce it, and explain how the couple can amend or revoke it after the wedding.[1]
A South Dakota prenuptial agreement must be in writing and signed by both parties, and it is enforceable without consideration.[1.2]
Notarize both signatures. Section 25-2-17 does not name a notary, but South Dakota practitioners commonly acknowledge a premarital agreement the way a conveyance of land is acknowledged. Notarizing costs little against the risk of a later fight over whether a signature is genuine.
Sign before the wedding. A contract signed after the ceremony is not a premarital agreement and does not fall under these sections, so couples who are already married use a postnuptial agreement instead.
After the wedding, a premarital agreement may be amended or revoked only by a written agreement signed by the parties. The amendment or the revocation is itself enforceable without consideration, so no payment between spouses is needed to make the change stick.[1.5]
Section 25-2-18 lists the subjects a couple may settle in a prenuptial agreement. The list is broad on property and deliberately narrow on everything else. It reaches property either partner already owns and property acquired later, the management of that property during the marriage, what happens to it on separation or death, and the estate planning that carries it out.[1.3]
Three limits sit outside the couple's control. Two come straight from the text of Section 25-2-18, which lists what a couple may agree on and then bounds that list. The exceptions protect a child's right to support and bar any matter that violates public policy or a criminal statute.[1.3] The third comes from how South Dakota courts have read that list, and it concerns spousal support.
Section 25-2-18 lists the subjects a couple may settle and spousal support is not among them.[1.3] In Sanford v. Sanford the South Dakota Supreme Court held that a clause waiving or limiting alimony is void as against public policy.
A judge decides support at divorce on the circumstances as they stand then. The rest of a properly drafted prenup survives, so a void support clause does not take the property terms down with it.
Child support and custody stay outside the document. Custody and visitation are decided on the child's best interests at the time, and a judge will not treat a term written years earlier as binding on that question.
Two defenses defeat a South Dakota prenuptial agreement, and the party resisting enforcement carries the burden of proving one of them. The first is that the party did not execute the agreement voluntarily. The second is that the agreement was unconscionable when it was executed, and that before signing the party was kept short of a fair and reasonable picture of the other side's finances.[1.6]
Section 25-2-21 sets out the grounds a judge looks for.
An issue of unconscionability is decided by the court as a matter of law.[1.6] It is therefore a question for the judge, not the jury.
Two further rules sit at the edges. 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.[1.7] Any statute of limitations on a claim under the agreement is tolled during the marriage.[1.8] Years spent married do not run down the clock on a later claim.
South Dakota is not a 50 50 divorce state. It follows equitable distribution, which means a judge divides marital property fairly on the facts of the case rather than splitting it down the middle. Fair can turn out to be equal, but nothing requires that result. A prenup is how a couple replaces that judicial discretion with their own written terms, agreed in advance.
That is the practical reason to sign one. Without a prenup, the equitable division is worked out at divorce on the circumstances as they stand then. With one, Section 25-2-18 lets you fix the rights and obligations in your property, and its disposition on separation, dissolution, or death, years before any of it is in dispute.[1.3] If the marriage does end, those terms are carried into a divorce settlement agreement.
Yes. South Dakota does not require a lawyer to draft or review prenuptial agreements. Section 25-2-17 asks only that the agreement be in writing and signed by both parties, and it makes it enforceable without consideration.[1.2]
What Chapter 25-2 polices is the process rather than the drafting. A judge can set the prenup aside if either party did not sign voluntarily, or if it was unconscionable and that party never got a fair picture of the other's finances.[1.6]
Both risks come from how the couple handles disclosure and timing, not from the wording of the clauses. Where the estate is large, or a business, farm, or ranch is involved, separate counsel for each partner costs less than the fight it prevents.
The two things that undo a South Dakota prenuptial agreement are involuntary signing and thin financial disclosure. Every step below closes off one of them. Work through the sequence in order, and keep a dated copy of what each of you disclosed. That record is the evidence a judge asks for when a prenup is challenged years later.
Last Updated: September 2026 This guide is reviewed and updated regularly to reflect current South Dakota law. If you notice an error or outdated information, please contact us.
