South Dakota: Prenuptial Agreement Requirements
The short answer
South Dakota uses the Uniform Premarital Agreement Act and requires a writing signed by both prospective spouses; no consideration, notary, witnesses, independent counsel, or statutory waiting period is required for basic validity. The agreement becomes effective upon marriage, but enforcement can fail for involuntary execution or for execution-time unconscionability combined with all three disclosure failures. A prenup cannot waive or limit spousal support, and it cannot adversely affect child support.
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This is the general rule in South Dakota. Ezel applies current South Dakota law to your specific facts and answers with citations to the statutes.
| Governing law and framework | Uniform Premarital Agreement Act, with South Dakota's support-waiver omission and case-law bar (SDCL §§ 25-2-16 to -25; Sanford) |
|---|---|
| Writing, signature, and effect | Writing signed by both; no consideration; effective upon marriage (§§ 25-2-17, -19) |
| Execution formalities | No statutory notary, acknowledgment, witness, or recording requirement for basic validity (§ 25-2-17) |
| Financial disclosure and waiver | Fair and reasonable disclosure; express written waiver or adequate knowledge can defeat the disclosure-based challenge (§ 25-2-21(a)(2)) |
| Independent counsel and timing | No statutory counsel/advisement requirement and no minimum review or pre-wedding period; voluntary execution still required (§§ 25-2-16 to -25) |
| Fairness standard and source | Statute — involuntary execution defeats enforcement; unconscionability at execution plus all three disclosure failures also defeats it; court decides unconscionability (§ 25-2-21) |
| Spousal-support limits | A premarital provision limiting or waiving spousal support is void and unenforceable, but may be severed (Sanford v. Sanford, 2005 SD 34, ¶ 38) |
| Child and public-policy limits | Cannot adversely affect child support; custody remains with the court under best interests; other terms cannot violate public policy or a criminal statute (§§ 25-2-18, 25-4-45) |
| Amendment and revocation | After marriage, only by a writing signed by both; no consideration required (§ 25-2-20) |
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Requirements one by one
South Dakota uses the Uniform Premarital Agreement Act
S.D. Codified Laws § 25-2-25 gives §§ 25-2-16 through 25-2-25 the short title
Uniform Premarital Agreement Act. Section 25-2-16 defines a premarital
agreement as one between prospective spouses, made in contemplation of marriage,
and intended to take effect upon marriage.
Under § 25-2-24, courts construe the act to make the law uniform
among states that enacted it.
South Dakota did not enact the model act word for word. Most importantly, it
left spousal-support contracting out of § 25-2-18, a deliberate omission the
South Dakota Supreme Court addressed in Sanford v. Sanford.
The agreement needs both signatures and marriage activates it
Section 25-2-17 states the basic form directly: a premarital agreement “shall
be in writing and signed by both parties.” It is enforceable without
consideration. Under § 25-2-19, the signed agreement becomes effective upon
marriage, not merely upon signing.
The act adds no notary, witness, or recording requirement
The statute titled “Formalities,” § 25-2-17, requires only the writing and both
signatures. Sections 25-2-16 through 25-2-25 add no acknowledgment, notary,
witness, attestation, or recording step for basic validity between the parties.
A notarized signature may help prove execution, but notarization is not one of
the act's stated validity requirements.
Disclosure uses three alternatives within the unconscionability test
Under § 25-2-21(a)(2), inadequate disclosure defeats enforcement through a
combined test. The agreement must have been unconscionable when signed, and the
challenging party must establish all three listed conditions: no fair and
reasonable disclosure, no voluntary express written waiver of further
disclosure, and no actual or reasonably available adequate knowledge.
The waiver must be voluntary, express, and in writing. The statute does not say
it must be a separate document.
Counsel and a pre-wedding interval are not statutory formalities
Sections 25-2-16 through 25-2-25 impose no independent-counsel mandate, written
counsel advisement, fixed review period, or minimum number of days between
signing and the wedding. That does not eliminate the separate requirement in
§ 25-2-21(a)(1) that execution be voluntary.
The statute supplies the enforcement test
The fairness source is statutory. Section 25-2-21 provides two routes to
nonenforcement: involuntary execution, or execution-time unconscionability
combined with all three disclosure failures. The court decides
unconscionability as a matter of law.
The statute does not create a general enforcement-time second look based only on
changed circumstances. Its unconscionability language points to when the
agreement was executed.
Spousal-support waivers are void
In Sanford v. Sanford, 2005 SD 34, ¶ 38, the South Dakota Supreme Court held
that a premarital provision purporting to limit or waive spousal support is void
and unenforceable as contrary to public policy. The court tied that result to the
Legislature's deliberate decision not to enact the model UPAA provision allowing
modification or elimination of support.
Child support and custody remain outside private control
Section 25-2-18(b) says a prenup may not adversely affect a child's right to
support. Section 25-4-45 keeps custody with the divorce court and directs it to
the child's best interests. Other personal-rights terms are allowed under
§ 25-2-18(a)(7) only if they do not violate public policy or a statute imposing
a criminal penalty.
Changes after marriage require another signed writing
Under § 25-2-20, amendment or revocation after marriage is possible only through
a written agreement signed by both parties. The amendment or revocation is
enforceable without consideration. The statute does not add notarization to this
change mechanism.
What trips people up
- A bad support clause does not necessarily destroy every property term.
Sanford held that a void support waiver may be severed from valid portions
without invalidating the entire agreement. - A notary does not replace financial disclosure. In Goeden v. Goeden,
2024 S.D. 51, one party signed a notarized agreement nine days before the
wedding, but the court still affirmed nonenforcement because undisclosed
retirement, health-savings, and bank assets left the statutory
unconscionability-and-disclosure test unsatisfied. - Marriage pauses a limitations period, but equitable delay defenses remain.
Under § 25-2-23, an applicable statute of limitations is tolled during the marriage
while preserving defenses such as laches and estoppel.
Common questions
Must the disclosure give exact values?
Not necessarily. Sanford, 2005 SD 34, ¶ 44, says a list of assets and
liabilities with approximate values may suffice if it gives the other spouse a
reasonable approximation of the magnitude of net worth.
Can the agreement address death and estate-planning arrangements?
Yes. Section 25-2-18(a) permits terms about property disposition at death, wills
or trusts used to carry out the agreement, and ownership or disposition of a
life-insurance death benefit.
What if the marriage is later determined to be void?
Section 25-2-22 limits an agreement that otherwise would have been a premarital
agreement to enforcement necessary to avoid an inequitable result.
Statutes and sources
- S.D. Codified Laws §§ 25-2-16, 25-2-24, and 25-2-25 — definition,
uniform construction, and short title. Official South Dakota
Legislature (accessed
2026-07-28). - S.D. Codified Laws §§ 25-2-17 and 25-2-19 — writing, signatures, no
consideration, and effectiveness upon marriage. Official §
25-2-17; official §
25-2-19 (accessed
2026-07-28). - S.D. Codified Laws § 25-2-18 — permitted subjects, public-policy limit,
and child-support protection. Official South Dakota
Legislature (accessed
2026-07-28). - S.D. Codified Laws § 25-2-21 — voluntariness, unconscionability,
disclosure, written waiver, adequate knowledge, and court decision. Official
South Dakota Legislature
(accessed 2026-07-28). - S.D. Codified Laws § 25-2-20 — amendment and revocation. Official South
Dakota Legislature
(accessed 2026-07-28). - S.D. Codified Laws §§ 25-2-22 and 25-2-23 — void marriages, limitations
tolling, and equitable defenses. Official §
25-2-22; official §
25-2-23 (accessed
2026-07-28). - S.D. Codified Laws § 25-4-45 — court-controlled custody and child best
interests. Official South Dakota
Legislature (accessed
2026-07-28). - Sanford v. Sanford, 2005 SD 34, 694 N.W.2d 283 — support-waiver bar,
severability, and disclosure precision. Opinion
text (accessed
2026-07-28). - Goeden v. Goeden, 2024 S.D. 51 — current application of the disclosure
and unconscionability test. Official South Dakota Unified Judicial System
opinion (accessed
2026-07-28).
Source links
Every statute quoted above, linked, with the date we checked it.
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