South Dakota Prenuptial Agreement
South Dakota prenuptial agreements are governed by the South Dakota Uniform Premarital Agreement Act (SDCL §§ 25-2-16 through 25-2-25), enacted in 1989. Courts apply single review only — unconscionability is assessed at signing, not at divorce. Two defenses permitted: involuntary execution or unconscionability plus disclosure failure. Approximate net worth suffices for disclosure; exact figures not required.
The critical weakness: South Dakota is one of only three states prohibiting prenuptial agreements from affecting spousal support in any form — no waivers, no caps, no formulas. Courts retain full alimony authority at divorce regardless of what the parties agreed.
Bottom line: South Dakota earns an F because it doesn't allow alimony, or spousal support, to be modified. A prenup still delivers substantial value — separate property is fully protected from South Dakota's all-property equitable distribution system, inheritance rights are waivable, and privacy terms are enforceable. Facing only alimony risk at divorce is far better than alimony plus full asset division.
South Dakota Prenup Enforceability Rating: F
South Dakota Prenup Laws: Key Statutes Explained
Uniform Premarital Agreement Act (UPAA), codified at SDCL §§ 25-2-16 through 25-2-25
Separate Property
All assets can remain separate property, avoiding costly divorce settlements. South Dakota is an "all-property" state — without a prenup, all property regardless of origin is subject to equitable division. Joint assets and debts titled in both names can be split 50/50 by agreement.
Unconscionability Single Review (Pro-Prenup)
South Dakota reviews prenuptial agreements for unconscionability ONLY at execution (signing), not at enforcement (divorce). This prevents courts from second-guessing agreements based on changed circumstances during marriage, providing greater certainty and discouraging litigation challenges.
Unconscionability Standard — SDCL § 25-2-21 Two-Prong Test
A prenup is unenforceable only if the challenging party proves: (1) involuntary execution; OR (2) the agreement was unconscionable at execution AND (a) lacked fair and reasonable disclosure of the other's property/obligations, (b) no written waiver of disclosure, AND (c) challenging party lacked adequate knowledge of the other's finances. Unconscionability is decided by the court as a matter of law.
Spousal Support — Cannot Be Waived
Unlike most states, South Dakota does not permit prenuptial agreements to waive, cap, or modify spousal support. Any such clause is void as against public policy and will be severed. Courts retain full authority to award alimony at divorce.
Timing
No minimum specified, but we recommend signing the prenup 60+ days before the wedding, with both parties having 2-3 weeks to review the final version to minimize challenge risk. Reach out to an attorney at least 4-6 months before the wedding with your draft prenup. Better yet, sign the prenup before proposing.
Independent Counsel
Not required, but separate counsel dramatically strengthens enforceability if the agreement is later challenged. South Dakota courts apply a totality-of-circumstances voluntariness test, and absence of counsel — particularly combined with any power or education disparity — weighs against enforcement.
Financial Disclosure
"Fair and reasonable disclosure" of assets and liabilities required under SDCL § 25-2-21, or written waiver. An approximate net worth schedule suffices — exact figures are not required — but omitting liabilities is a common and fatal drafting error.
Moderate Burden to Challenge
Challenging party must prove either involuntary execution or unconscionability plus lack of disclosure. South Dakota courts do not conduct a second fairness review at divorce. Webb (2026) confirms that sophistication and a meaningful opportunity to seek counsel weigh heavily toward enforcement, even when an agreement is presented close to the wedding.
Child Support and Custody
Child support and custody clauses are unenforceable and could undermine the entire agreement. Do not include.
South Dakota Prenuptial Agreement Court Cases
Connolly v. Connolly, 270 N.W.2d 44 (S.D. 1978)
The court invalidated an antenuptial alimony waiver as contrary to South Dakota public policy, establishing the categorical rule — still controlling today — that spousal support cannot be contracted away in a prenuptial agreement.
Smetana v. Smetana, 2007 SD 5, 726 N.W.2d 887
The court invalidated an antenuptial agreement where the husband provided no list of assets or liabilities at any time, holding that general courtship-era awareness of asset categories is insufficient disclosure without an approximate net worth figure that also captures liabilities.
In re Estate of Eichstadt, 2022 SD 78, 983 N.W.2d 572
The court found a premarital agreement involuntarily signed where the wife had limited education, no independent counsel, was brought to the drafting attorney's office without prior notice of the prenup, and credibly testified she did not understand what she was signing.
Sanford v. Sanford, 2005 SD 34, 694 N.W.2d 283
The court voided the alimony waiver in a prenup between a $55M-net-worth husband and a $127,500-net-worth wife but enforced the property division provisions, holding that an invalid spousal support clause is severable from otherwise valid property terms when the agreement contains a savings clause and property protection was clearly the agreement's core purpose.
In re Estate of Smid, 2008 SD 82, 756 N.W.2d 1
The court enforced a premarital agreement where the surviving wife claimed she signed only to "avoid probate," holding that voluntariness requires a totality-of-circumstances analysis and that failing to fully read or understand an agreement — absent fraud or coercion — does not render execution involuntary.
In re Estate of Webb, 2026 SD 2
The court enforced a prenuptial agreement presented to the wife the day before the wedding, distinguishing Eichstadt on the grounds that the wife held a college degree, had business management experience, actively engaged with the document's asset schedules, and had a meaningful opportunity to seek independent counsel.
5-Step Checklist: How to Sign & Execute a Prenup in South Dakota
Step 1: Download and read the South Dakota prenuptial agreement
Start with our free template. It is written for South Dakota-specific statutes and case law under SDCL §§ 25-2-16 through 25-2-25 (Uniform Premarital Agreement Act). Read it in full — know what you are getting into legally with marriage. The 15+ pages is written thoroughly to include rebuttals to common legal challenges and fallback provisions.
Step 2: Draft changes on your own
See a clause you don't like? Copy it into an AI like Claude, explain what you'd like to change or what you want the clause "to do." Save any changes as a separate alternate version — don't overwrite the original. Bring both versions to your attorney review. Note: AI is often gender-biased and crafts terms beyond what is legally required. Push back on its output. Do not include spousal support clauses — they are void under South Dakota law and will be severed.
Step 3: Find a matrimonial or divorce lawyer in South Dakota
Find a matrimonial or divorce attorney in your state. Avvo, Findlaw, and Justia are good. Look for someone with 10+ years experience. Call or email and ask them how much to review your draft prenup and help with signing. Send them your draft.
Step 4: Meet your lawyer 4–6 months before the wedding
Our recommendation: sign the prenup before proposing. That way, you both get the legal work out of the way, and you know this is the right person to marry. Already proposed? 4–6 months before the wedding should leave you enough time to give your spouse 1–2 weeks to review the final draft and have it signed 60+ days before the wedding.
Step 5: Review and sign the prenup with your attorney
South Dakota does not require notarization by statute, but it is strongly recommended. Both attorneys present can witness and notarize on the spot, satisfying best practices in one signing ceremony. We HIGHLY recommend having the prenup reviewed and signed with an attorney — absence of independent counsel is a significant factor in voluntariness challenges. Each party keeps a signed original, and so should each party's attorney.
South Dakota Prenuptial Agreement: Frequently Asked Questions (2026)
1. Is a prenuptial agreement enforceable in South Dakota?
Yes. South Dakota prenuptial agreements are enforceable under the Uniform Premarital Agreement Act, SDCL §§ 25-2-16 through 25-2-25, enacted in 1989. To be enforceable, the agreement must be in writing, signed by both parties, entered into voluntarily, and accompanied by fair and reasonable financial disclosure. Courts enforce valid prenups without conducting a second fairness review at divorce — if the agreement was legitimate when signed, it stands.
2. What can a prenuptial agreement cover in South Dakota?
A South Dakota prenup can cover: classification and division of separate and marital property; management and control of property during marriage; disposition of assets at divorce or death; inheritance rights and estate planning provisions; premarital debt responsibility; life insurance beneficiary designations; and choice of law. It cannot waive or modify spousal support, determine child custody, or set child support — those are reserved for the courts.
3. Can a prenuptial agreement waive alimony in South Dakota?
No — and this is South Dakota's most important departure from other states. Spousal support waivers, caps, and formulas are void as against public policy under Connolly v. Connolly (1978) and Sanford v. Sanford (2005). The legislature deliberately omitted the alimony-waiver provision when adopting the UPAA in 1989. Courts retain full authority to award alimony at divorce regardless of what the prenup says. Any such clause will be severed; a strong severability clause protects the rest of the agreement.
4. Does a prenuptial agreement need to be notarized in South Dakota?
Notarization is not required by statute under SDCL § 25-2-17 — only writing and signatures are mandatory. However, notarization is strongly recommended. It creates a presumption of authenticity, makes it harder to later claim a signature was forged or coerced, and adds a procedural layer that courts view favorably when evaluating voluntariness. Both attorneys can notarize at the signing ceremony at no additional cost.
5. Does South Dakota require a lawyer for a prenuptial agreement?
No. Independent legal counsel is not required by statute. However, it is one of the most important factors courts examine when a prenup is challenged. South Dakota uses a totality-of-circumstances test for voluntariness (In re Estate of Smid, 2008), and the absence of counsel — especially combined with any education gap or power disparity between the parties — significantly increases challenge risk. Eichstadt (2022) invalidated an agreement partly because the wife had no independent attorney. Both parties should have their own separate counsel.
6. How do South Dakota courts decide if a prenuptial agreement is invalid?
Under SDCL § 25-2-21, the burden falls on the challenging party to prove either: (1) the agreement was not executed voluntarily, or (2) the agreement was unconscionable at execution AND the challenging party lacked fair financial disclosure, did not waive disclosure in writing, and had no adequate independent knowledge of the other party's finances. Crucially, unconscionability is judged only at the time of signing — not at divorce. Courts do not re-examine fairness based on how circumstances changed during the marriage.
7. Can a prenuptial agreement protect a farm, ranch, or family business in South Dakota?
Yes, and this is one of the most common and important uses of prenups in South Dakota. Without one, South Dakota's "all-property" rule subjects all assets — including farms, ranches, and businesses brought into the marriage — to equitable division at divorce, regardless of title or origin. A prenup can designate these as separate property, specify how any appreciation in value is treated, and protect multi-generational assets from division. The prenup must include an asset schedule listing the property and its approximate value at signing.
8. How much financial disclosure is required in a South Dakota prenuptial agreement?
South Dakota requires "fair and reasonable disclosure" of assets and financial obligations under SDCL § 25-2-21, or a written waiver of the right to further disclosure. Courts do not require exact figures — an approximate net worth schedule listing assets and liabilities with reasonable valuations satisfies the standard (Sanford, 2005; Smetana, 2007). Critically, liabilities must be disclosed, not just assets. Omitting debts is one of the most common and fatal drafting errors, as Smetana demonstrates.
9. Can a prenuptial agreement protect an inheritance in South Dakota?
Yes. This is particularly valuable in South Dakota, which is an all-property state — meaning inherited assets, even pre-marital ones, are technically subject to equitable division by a court. A prenup can expressly designate inheritances (received before or during marriage) as separate property, exclude them from the marital estate, and ensure they pass to children from prior relationships. Without a prenup, there is no automatic statutory protection for inherited property in a South Dakota divorce.
10. How far in advance should a prenuptial agreement be signed in South Dakota?
South Dakota has no statutory minimum, but timing is one of the most litigated challenge grounds. Eichstadt (2022) highlighted last-minute presentation as a key factor in finding involuntariness. Best practice is to sign 60+ days before the wedding, with both parties having 2–3 weeks to review the final draft. Start with an attorney 4–6 months before the wedding. Ideally, sign before proposing — it completely eliminates any argument that wedding-day pressure influenced the agreement.