Couples in Sioux Falls, Rapid City, and Aberdeen are signing prenuptial agreements more often than they used to, and not because anyone expects the marriage to fail.
Not legal advice. This article is general information only. Prenup laws differ by state and change over time. Consult a licensed attorney in your state before acting on anything here.
A prenup is a planning document. It sets out who owns what, what stays separate, and how things would be sorted out if the marriage ever ended.
South Dakota has its own rules for these agreements, written into the South Dakota Codified Laws. Knowing those rules is what separates a prenup that holds up from one a judge sets aside.
This guide walks through how prenups work in South Dakota, what they can and cannot do, and how to put one together correctly.
Do Prenuptial Agreements Hold Up in South Dakota?
Yes. South Dakota enforces prenuptial agreements under the Uniform Premarital Agreement Act, adopted by the state in 1989.
The Act lives in South Dakota Codified Laws Chapter 25-2, in sections 25-2-16 through 25-2-25. Section 25-2-25 confirms that these sections may be cited as the Uniform Premarital Agreement Act.
Under SDCL 25-2-16, a premarital agreement is an agreement between prospective spouses made in contemplation of marriage and to be effective upon marriage.
A South Dakota court starts from the position that a signed prenup is valid. The spouse who wants out has to prove a specific legal ground for setting it aside.
The Two-Part Test Under Section 25-2-21
SDCL 25-2-21 sets the bar for throwing out a prenup. The agreement is not enforceable only if the party challenging it proves one of two things.
- That party did not execute the agreement voluntarily, meaning it was signed under duress, fraud, or coercion.
- The agreement was unconscionable when it was executed, and one of three disclosure failures also occurred before signing.
The second ground requires the unconscionability and at least one disclosure failure together. The challenging party must show that, before signing, they:
- Were not provided a fair and reasonable disclosure of the other party’s property or financial obligations.
- Did not voluntarily and expressly waive that disclosure in writing.
- Did not have, and could not reasonably have had, adequate knowledge of the other party’s property or finances.
Section 25-2-21 also states that whether an agreement is unconscionable is decided by the court as a matter of law, not by a jury.
What a South Dakota Prenup Can Cover
SDCL 25-2-18 lists the matters spouses may contract about. The list is broad and covers most financial planning a couple would want.
| Area | What You Can Decide |
|---|---|
| Property rights | Each party’s rights and obligations in any property of either or both, whenever and wherever acquired |
| Managing assets | The right to buy, sell, use, transfer, mortgage, encumber, or otherwise control property |
| Division at the end | How property is handled on separation, divorce, death, or another named event |
| Estate planning | Making a will, trust, or other arrangement to carry out the agreement |
| Life insurance | Ownership and disposition of a life insurance policy death benefit |
| Governing law | The choice of law used to interpret the agreement |
| Other matters | Any other matter, including personal rights, that does not violate public policy or a criminal statute |
What a South Dakota Prenup Cannot Do
The same statute and South Dakota case law place firm limits on a prenup. A few terms will not stand no matter how the document is written.
- It cannot adversely affect a child’s right to support, which SDCL 25-2-18 protects directly.
- It cannot decide child custody or parenting time, since a court resolves those on the best interests of the child at the time of divorce.
- It cannot include terms that violate public policy or any statute carrying a criminal penalty.
- It cannot reliably waive alimony, which South Dakota courts treat as a public policy matter discussed below.
Execution Rules for a South Dakota Prenup
The formal rules are short, and they come straight from the statute. SDCL 25-2-17 covers how the agreement must be made.
| Requirement | South Dakota Rule |
|---|---|
| Written document | Required under SDCL 25-2-17; an oral prenup is not enforceable |
| Signatures | Signed by both parties under SDCL 25-2-17 |
| Consideration | Not needed; the agreement is enforceable without consideration |
| Effective date | Becomes effective upon marriage under SDCL 25-2-19 |
| Notarization | Not required by statute, though many couples notarize for proof |
| Changes later | Amended or revoked only by a later written agreement signed by both, under SDCL 25-2-20 |
Can You Waive Alimony in South Dakota?
This is where South Dakota stands apart from many states. The short answer is that you usually cannot.
The South Dakota Supreme Court has held that provisions in a prenuptial agreement that limit or waive spousal support are against public policy and unenforceable.
That rule comes from Connolly v. Connolly, 270 N.W.2d 44 (S.D. 1978), and was reaffirmed in Sanford v. Sanford, 2005 SD 34, 694 N.W.2d 283.
In Sanford, the court struck the alimony waiver but kept the rest of the agreement, because the waiver could be severed from the valid property terms.
So a South Dakota prenup can divide property cleanly, but a clause cutting off alimony is likely to be voided if challenged. A separate property judge keeps the power to award support.
Full Financial Disclosure in South Dakota
Disclosure is the heart of an enforceable prenup. SDCL 25-2-21 ties enforceability to whether each party had a fair and reasonable account of the other’s finances.
You do not need exact dollar figures for every asset. Each party should give the other a list of assets and liabilities with approximate values that show a reasonable view of net worth.
The safest practice is to attach a signed schedule of assets, debts, and income for each person to the agreement itself.
If a spouse later proves the agreement was unconscionable and that disclosure was missing, the prenup can fail under the two-part test. Honest, written disclosure removes that risk.
What Happens in South Dakota Without a Prenup
Without a prenup, a divorce court divides property under SDCL 25-4-44. South Dakota is an equitable distribution state, which means a fair split, not an automatic 50/50.
The statute reaches further than most people expect. Under SDCL 25-4-44, a court may divide the property belonging to either or both spouses, whether title is held by the husband or the wife.
South Dakota is an all-property state. Because the statute covers property of either spouse however held, a court can reach assets you brought into the marriage and even property you inherited.
The statute directs the court to have regard for equity and the circumstances of the parties. That gives a judge wide discretion over what each spouse keeps.
A prenup is how you replace that discretion with your own plan, setting in advance what stays separate and what gets shared.
South Dakota Prenup vs. Postnup
A prenup is signed before the wedding and becomes effective on marriage. A postnup is signed after a couple is already married.
South Dakota’s Uniform Premarital Agreement Act in Chapter 25-2 applies to premarital agreements, not to postnups. Spouses can still contract with each other, since SDCL 25-2-1 allows it.
South Dakota courts have recognized postnuptial agreements, but they sit outside the clean statutory framework that governs prenups.
Because of that, a postnup can draw closer scrutiny on fairness and disclosure. If you can plan before the wedding, a prenup gives you the more settled legal footing.
Have a South Dakota attorney review either one.
Common Reasons South Dakota Prenups Get Thrown Out
Most failed prenups fail for avoidable reasons. The patterns below track directly with the grounds in SDCL 25-2-21.
- One spouse signed under pressure, such as an agreement presented days before the wedding with no time to review.
- Financial disclosure was incomplete or hidden, leaving a spouse without adequate knowledge of the other’s assets.
- The agreement was unconscionable when signed and a disclosure failure occurred alongside it.
- The document tried to waive alimony, which South Dakota courts treat as void on public policy grounds.
- The prenup tried to limit child support or decide custody, which the law does not allow.
- One party had no chance to consult independent counsel.
How Much Does a Prenup Cost in South Dakota?
Cost depends on how complex your finances are and whether you hire attorneys or use an online service.
| Option | Typical Cost | Best For |
|---|---|---|
| Attorney drafted | 1,500 to 5,000 per person | Standard prenups with independent review |
| Complex estates | 2,000 to 7,000 per person | Business owners, trusts, large or mixed assets |
| Online service | A few hundred dollars, flat | Straightforward finances on a budget |
An online platform such as HelloPrenup lets each partner build the agreement together for a flat fee, which can cost far less than two attorneys.
Even with an online draft, having a South Dakota attorney review the final document is money well spent, especially given the state’s alimony rule.
How to Create a South Dakota Prenup, Step by Step
The process is straightforward when you take it in order and leave enough time before the wedding.
- Start early, ideally several months before the wedding, so no one can later claim they were rushed.
- Each partner prepares a full written list of assets, debts, and income.
- Talk through what stays separate, what is shared, and how property would be divided.
- Draft the agreement, through an attorney or an online service, in line with Chapter 25-2.
- Have each partner review the draft with independent counsel where possible.
- Sign the written agreement before the wedding, and consider notarizing it for proof.
- Store signed copies safely, with the asset schedules attached.
Final Thoughts on a South Dakota Prenup
A South Dakota prenup is a clear, lawful way to decide property questions in advance instead of leaving them to a judge under SDCL 25-4-44.
Get the basics right, and the agreement will hold. Put it in writing, sign before the wedding, disclose finances honestly, and respect the limits on child support and alimony.
Keep in mind the state’s strong rule against alimony waivers, and have the final document reviewed by a South Dakota attorney.
Done well, a prenup is simply a sign of two people planning their future together with open eyes.
Sources
- South Dakota Codified Laws, Chapter 25-2 (Uniform Premarital Agreement Act)
- SDCL 25-2-21, Enforcement of premarital agreements
- SDCL 25-2-18, Content of premarital agreements
- SDCL 25-4-44, Division of property between parties
- Sanford v. Sanford, 2005 SD 34, 694 N.W.2d 283; Connolly v. Connolly, 270 N.W.2d 44 (S.D. 1978)