Prenuptial Agreements in South Dakota: Complete 2026 Legal Guide

Answer Capsule

South Dakota prenuptial agreements must be in writing and signed by both parties before marriage under the Uniform Premarital Agreement Act (SDCL 25-2-16 through 25-2-25). The agreement becomes effective only upon marriage and does not require notarization, though notarization is recommended. South Dakota uniquely prohibits spousal support waivers in prenups per SDCL 25-2-18, making it one of the few states where alimony provisions are unenforceable. Attorney fees typically range from $1,500 to $3,500 for prenup preparation, with online platforms offering services starting at $599 as of March 2026.

Key Facts: South Dakota Prenuptial Agreements

What Is a Prenuptial Agreement in South Dakota

A prenuptial agreement in South Dakota is a written contract signed by two people before marriage that determines how property and financial matters will be handled during marriage and in the event of divorce or death. South Dakota recognizes prenuptial agreements under the Uniform Premarital Agreement Act, codified in SDCL 25-2-16 through SDCL 25-2-25, which was adopted by the National Conference of Commissioners on Uniform State Laws in 1983. The agreement becomes effective only on the official wedding day and requires no additional consideration beyond the marriage itself to be valid. South Dakota is an equitable distribution state and an all-property state, meaning courts divide all marital property fairly rather than equally, and even premarital assets, inheritances, and gifts may be subject to division without a prenup.

Unlike most states, South Dakota imposes a critical limitation on prenuptial agreements. Under SDCL 25-2-18 and established case law including Sanford v. Sanford, 694 N.W.2d 283 (2005), spousal support provisions in prenuptial agreements are unenforceable. The South Dakota Supreme Court has consistently held that alimony waivers violate public policy, making South Dakota one of the most restrictive states regarding spousal support provisions in premarital agreements. This means couples can contractually protect property rights but cannot limit future alimony obligations through a prenuptial agreement.

Legal Requirements for Valid Prenups in South Dakota

South Dakota prenuptial agreements must satisfy four mandatory requirements under SDCL 25-2-16 to be legally enforceable. First, the agreement must be in writing and signed by both parties before the marriage ceremony. Oral prenuptial agreements have no legal effect in South Dakota regardless of witnesses or other evidence. Second, both parties must enter into the agreement voluntarily without coercion, duress, fraud, or undue influence. Third, the agreement must not be unconscionable at the time of execution, meaning it cannot be so one-sided that it shocks the conscience of the court. Fourth, both parties must provide full and fair disclosure of their assets, debts, and income, or the party against whom enforcement is sought must have voluntarily waived disclosure in writing after having adequate opportunity to obtain independent information.

South Dakota courts apply a two-part test to determine enforceability under SDCL 25-2-20. A premarital agreement is unenforceable if the party seeking to avoid enforcement proves that they did not execute the agreement voluntarily, OR if they prove both that: (1) the agreement was unconscionable when executed, AND (2) before execution they were not provided fair and reasonable disclosure of the other party's property or financial obligations, did not voluntarily waive disclosure in writing, and did not have adequate knowledge of the property or financial obligations. This standard creates a strong presumption of enforceability once the agreement is signed, placing the burden on the challenging party to demonstrate specific defects. Courts do not review prenuptial agreements for general fairness at the time of divorce unless these statutory grounds are established.

Notarization is not required for validity in South Dakota, but legal practitioners strongly recommend notarizing prenuptial agreements to create a presumption of proper execution and to facilitate enforcement. South Dakota law allows electronic notarization, and notaries must physically witness the parties sign the document. While SDCL 25-2-16 does not mandate independent legal counsel for each party, courts consider whether both parties had the opportunity to consult with separate attorneys when evaluating voluntariness and whether adequate disclosure occurred. The absence of independent counsel does not automatically invalidate a prenuptial agreement but can be a significant factor if other defects exist.

What Can and Cannot Be Included

South Dakota prenuptial agreements can address property division, inheritance rights, business interests, and debt allocation, but cannot include provisions regarding child custody, child support, or spousal support. Under SDCL 25-2-18, parties may contract regarding the rights and obligations of each in property owned by either of them, the right to buy, sell, use, transfer, exchange, abandon, lease, consume, expend, assign, create a security interest in, mortgage, encumber, dispose of, or otherwise manage property, the disposition of property upon separation, marital dissolution, death, or the occurrence of any other event, the modification or elimination of spousal support (this provision is unenforceable per case law), the making of a will, trust, or other arrangement to carry out the agreement, the ownership rights and disposition of death benefits from a life insurance policy, and any other matter not in violation of public policy or criminal statute.

The most significant limitation is the unenforceability of spousal support provisions. In Sanford v. Sanford, 694 N.W.2d 283 (2005), the South Dakota Supreme Court held that SDCL 25-2-18 prohibits waiver or modification of alimony in prenuptial agreements because such provisions violate the state's public policy of ensuring courts retain discretion to award support based on circumstances at the time of divorce. The court ruled that even though the statute appears to allow spousal support provisions, case law interpretation renders them void. Similarly, in Connolly v. Connolly, the court reaffirmed that alimony provisions in prenuptial agreements are unenforceable regardless of the agreement's language.

Child-related provisions are similarly prohibited under SDCL 25-2-18. Prenuptial agreements cannot predetermine child custody arrangements, parenting time schedules, or child support amounts because South Dakota law requires courts to determine these matters based on the best interests of the child at the time of divorce or separation under SDCL 25-4-45 and SDCL 25-7-6.2. Any provision attempting to waive or limit child support is void as against public policy. Courts may also decline to enforce attorney fee provisions in prenuptial agreements as they pertain to spousal support disputes, meaning a clause stating each party pays their own legal fees may be invalidated if it relates to alimony litigation.

Prenuptial agreements can effectively protect separate property, define how property acquired during marriage will be classified, establish provisions for business valuation and division, allocate specific assets or debts to each spouse, waive inheritance rights under SDCL 29A-2-213, and create procedures for resolving disputes through mediation or arbitration. These provisions are enforceable provided they meet the voluntariness, disclosure, and conscionability requirements. South Dakota's status as an all-property state makes prenuptial agreements particularly valuable because without a prenup, courts can divide premarital assets, inheritances, and gifts that would be considered separate property in most other equitable distribution states.

Financial Disclosure Requirements

South Dakota law mandates full and fair financial disclosure or a valid written waiver before executing a prenuptial agreement under SDCL 25-2-20. Each party must disclose all assets, liabilities, income sources, and significant financial obligations before signing the agreement. Disclosure must be sufficiently detailed to allow the other party to make an informed decision about the agreement's terms. General statements like "I own substantial assets" or "I have significant retirement savings" do not satisfy the disclosure requirement. Instead, parties should provide specific account balances, property valuations, debt amounts, income figures, and business interests with reasonable accuracy.

The disclosure requirement serves two purposes: ensuring both parties enter the agreement with full knowledge of the other's financial circumstances, and preventing enforcement of unconscionable agreements. A prenuptial agreement can still be enforceable without full disclosure if the party against whom enforcement is sought voluntarily and expressly waived disclosure in writing after having adequate opportunity to obtain independent information about the other party's finances. For example, if one party's attorney advised them to request financial documents but the party declined and signed a written waiver, the agreement may be enforceable even without disclosure. However, courts scrutinize waivers carefully and may find them invalid if the waiving party did not have reasonable access to information or did not understand the scope of what was being waived.

South Dakota courts consider several factors when evaluating disclosure adequacy. These include whether asset valuations were current and accurate, whether both parties had time to review financial information before signing, whether complex assets like businesses were properly valued or explained, whether one party had superior knowledge of finances and took advantage of the other party's lack of sophistication, and whether the parties attached financial statements or schedules to the prenuptial agreement. Best practice involves attaching detailed financial schedules listing all assets and liabilities with specific values, obtaining professional appraisals for significant property like real estate or businesses, updating disclosure if substantial financial changes occur between drafting and execution, and documenting that both parties received copies of all financial information at least 30 days before signing.

Failure to provide adequate disclosure can result in the entire prenuptial agreement being unenforceable if the agreement is also unconscionable at the time of execution. Courts will examine the totality of circumstances including the parties' relative financial sophistication, the complexity of the parties' assets, the time between disclosure and execution, whether the parties discussed finances openly during the engagement, and whether independent attorneys reviewed the disclosure. Even if disclosure was incomplete, the agreement may be enforceable if it was not unconscionable or if the party seeking to avoid enforcement had actual knowledge of the other's finances through other means such as joint account statements or business involvement.

How South Dakota Property Division Works Without a Prenup

South Dakota is an equitable distribution state under SDCL 25-4-44, meaning courts divide marital property fairly rather than equally in divorce cases. South Dakota is also an all-property state, which means there is no automatic exemption for separate property, and judges can divide all property owned during the marriage regardless of when or how it was acquired. This includes premarital assets, inheritances, and gifts that would be excluded from division in most other equitable distribution states. Without a prenuptial agreement, all property owned by either spouse is potentially subject to division, giving courts broad discretion to allocate assets based on equity rather than title or source.

South Dakota has no statutory guidelines listing specific factors courts must consider when dividing property, giving judges significant flexibility in determining equitable distribution. South Dakota case law has established common factors including the duration of the marriage, the value of property owned by each spouse, each spouse's age and health, each spouse's earning capacity and future financial prospects, the contribution of each spouse to the accumulation of property including homemaking and childrearing contributions under SDCL 25-4-44, the income-producing capacity of assets awarded to each spouse, and evidence of economic misconduct such as dissipation of marital assets. Courts particularly value nonmonetary contributions, and a stay-at-home spouse's domestic labor is considered equivalent to financial contributions when determining property division.

In practice, judges in equitable distribution states like South Dakota often divide marital property with approximately two-thirds (66%) of marital assets going to the higher-earning spouse and one-third (33%) going to the lower-earning spouse, though this is not a fixed rule. The actual division depends heavily on case-specific factors. For example, in a 25-year marriage where one spouse worked while the other raised children, the court might award 50% to each spouse regardless of who earned the income. Conversely, in a 3-year marriage where both spouses worked and kept finances separate, the court might award 70-80% to the spouse who accumulated more assets during the marriage.

The all-property designation creates significant uncertainty for individuals entering marriage with substantial premarital assets, inheritances, or family businesses. For instance, if one party inherits a $500,000 family farm before marriage, that entire property could be subject to division in a divorce even though it was never marital property in the traditional sense. Similarly, if one spouse owns a business worth $2 million before marriage and the business grows to $5 million during a 15-year marriage, the entire $5 million value could potentially be divided equitably rather than just the $3 million increase. This all-property approach makes prenuptial agreements particularly valuable in South Dakota for protecting premarital wealth and family inheritances.

The Alimony Waiver Prohibition: South Dakota's Unique Rule

South Dakota is one of the few states that completely prohibits spousal support provisions in prenuptial agreements, creating a critical limitation that distinguishes South Dakota from most other jurisdictions. Under SDCL 25-2-18 and controlling case law, any provision in a prenuptial agreement that attempts to waive, limit, or modify spousal support is void and unenforceable. This prohibition stems from the public policy principle that courts must retain discretion to award alimony based on circumstances at the time of divorce rather than agreements made years earlier under different financial conditions.

The leading case establishing this rule is Sanford v. Sanford, 694 N.W.2d 283 (South Dakota Supreme Court, 2005), where the court held that even though SDCL 25-2-18 appears to allow parties to contract regarding "modification or elimination of spousal support," this provision conflicts with the state's public policy of ensuring dependent spouses receive appropriate support. The court ruled that the spousal support portion of the prenuptial agreement was invalid while the property division provisions remained enforceable, demonstrating that courts will sever unenforceable alimony clauses rather than void the entire agreement. The court specifically stated that it did not matter what the prenuptial agreement said about alimony because such provisions are unenforceable as a matter of law.

This rule was reaffirmed in Connolly v. Connolly, where the South Dakota Supreme Court again held that alimony provisions in prenuptial agreements violate public policy and cannot be enforced. The reasoning is that spousal support serves important public interests beyond the private contract rights of divorcing parties, including preventing one spouse from becoming a public charge, recognizing economic sacrifices made during marriage (particularly by homemakers), and ensuring financially dependent spouses can maintain a reasonable standard of living post-divorce. Allowing parties to waive these protections years in advance could lead to unconscionable results if circumstances change dramatically during the marriage.

The practical implications of this rule are significant. Couples entering marriage with substantial income disparities cannot contractually limit future alimony obligations through a prenuptial agreement. For example, if a high-earning executive earning $500,000 annually marries a teacher earning $45,000 annually, the executive cannot include a prenup provision stating "no spousal support will be awarded in the event of divorce." If the marriage ends after 15 years during which the teacher reduced work hours to raise children, a South Dakota court will award spousal support based on statutory factors under SDCL 25-4-41 regardless of any prenuptial agreement language. This makes South Dakota prenuptial agreements less comprehensive than in states allowing spousal support waivers, though property division provisions remain fully enforceable and can significantly impact the financial outcome of divorce.

Attorney fee provisions related to spousal support disputes may also be unenforceable. Some South Dakota courts have ruled that clauses requiring each party to pay their own attorney fees are invalid when those fees relate to alimony litigation, reasoning that attorney fee awards are ancillary to spousal support and thus subject to the same public policy limitations. This means even procedural cost-shifting provisions may be invalidated if they relate to support rather than property division.

Voluntariness and Unconscionability Standards

South Dakota courts apply strict standards for voluntariness when evaluating prenuptial agreements under SDCL 25-2-20. An agreement is not voluntary if executed under duress, coercion, fraud, undue influence, or overreaching by one party. Courts examine the totality of circumstances surrounding execution including the time between presentation and execution (agreements presented hours before the wedding are presumptively involuntary), whether both parties had opportunity to consult independent legal counsel, the parties' relative bargaining power and financial sophistication, whether one party pressured the other with threats or ultimatums, and whether the agreement was presented as non-negotiable or take-it-or-leave-it.

The timing of prenuptial agreement presentation is particularly important in South Dakota. Courts have found agreements involuntary when presented shortly before the wedding ceremony when canceling the wedding would cause significant embarrassment, financial loss from non-refundable deposits, and emotional distress. Best practice recommends presenting the prenuptial agreement at least 30-60 days before the wedding date to demonstrate voluntariness. This allows adequate time for review, consultation with independent counsel, negotiation of terms, and consideration without the pressure of an imminent wedding. Agreements presented 3-7 days before the wedding face heightened scrutiny and may be found involuntary if other factors suggest coercion.

The unconscionability standard under SDCL 25-2-20 examines whether the agreement is so one-sided that it shocks the conscience of the court at the time of execution, not at the time of divorce. This is a demanding standard that requires extreme unfairness rather than mere imbalance. South Dakota courts consider several factors including the relative financial positions of the parties at execution, whether one party receives substantially all marital assets while the other receives little or nothing, whether the agreement leaves one party destitute or unable to meet basic needs, the parties' ages, health, and earning capacities at execution, and whether the agreement's terms are grossly disproportionate to what would be awarded under South Dakota's equitable distribution laws.

An example of a potentially unconscionable prenuptial agreement would be one where a 65-year-old executive worth $10 million marries a 25-year-old with minimal assets and income, presents an agreement giving her only $50,000 in the event of divorce regardless of marriage duration, provides minimal financial disclosure, and discourages her from consulting an attorney. Such an agreement might be unconscionable because it leaves the younger spouse with grossly inadequate resources while the older spouse retains virtually all wealth. However, unconscionability alone is insufficient to invalidate the agreement under SDCL 25-2-20; the challenging party must also prove lack of adequate disclosure or knowledge of the other party's finances.

Importantly, South Dakota courts evaluate unconscionability at the time of execution, not at the time of divorce. An agreement that becomes unfair due to changed circumstances during the marriage is still enforceable if it was conscionable when signed and met all other statutory requirements. For example, if a prenuptial agreement provides that each spouse keeps their own retirement accounts, and during a 20-year marriage one spouse accumulates $2 million in retirement while the other accumulates only $100,000 due to career sacrifices for childcare, the agreement remains enforceable even though the result is now imbalanced. This rule incentivizes parties to carefully consider long-term implications and future scenarios when drafting prenuptial agreements.

Amendment and Revocation of Prenuptial Agreements

South Dakota prenuptial agreements can be amended or revoked after marriage under SDCL 25-2-19, but only through a written agreement signed by both parties. Oral agreements to modify or revoke a prenuptial agreement have no legal effect regardless of the parties' intentions or actions. The amendment or revocation does not require consideration beyond the parties' mutual consent, meaning no additional exchange of value is necessary for the modification to be binding. This allows couples to update their prenuptial agreements as circumstances change during marriage without needing to structure the amendment as a separate contract with new consideration.

Amendments must be executed with the same formalities as the original prenuptial agreement including written form, signatures by both parties, and voluntariness. While notarization is not required for amendments under South Dakota law, legal practitioners strongly recommend notarizing amendments to establish proper execution and facilitate future enforcement. Amendments should specifically reference the original prenuptial agreement by date and parties' names, clearly state which provisions are being modified or deleted, include any new provisions in detail, and include a severability clause stating that if any provision is unenforceable, the remaining provisions remain valid.

Complete revocation of a prenuptial agreement requires explicit written language such as "The prenuptial agreement dated [date] between [Party A] and [Party B] is hereby revoked in its entirety and shall have no further force or effect." Partial revocation language should specifically identify which provisions are revoked. Informal conduct does not constitute revocation; for example, if a prenuptial agreement states each spouse keeps their separate property and the couple subsequently commingles all assets in joint accounts, the agreement remains enforceable unless formally revoked in writing. The commingling may affect how specific assets are classified, but it does not revoke the underlying agreement.

Couples should consider amending prenuptial agreements when significant life changes occur including birth or adoption of children requiring updated estate planning provisions, substantial changes in either party's income or assets, inheritance of significant property, starting or selling a business, moving to a different state with different marital property laws, or retirement with changes in income sources and asset management. Postnuptial agreements (agreements executed after marriage) are also permitted in South Dakota and governed by similar principles as prenuptial agreements, though they may face slightly different legal analysis regarding consideration and voluntariness since the parties are already married when executing the agreement.

Cost of Prenuptial Agreements in South Dakota

The cost of creating a prenuptial agreement in South Dakota varies significantly based on the attorney's experience, the complexity of the parties' financial situations, geographic location within the state, and whether negotiations are contentious or cooperative. Attorney fees for traditional prenuptial agreement preparation range from $1,500 to $3,500 per party as of March 2026, meaning a couple could pay $3,000 to $7,000 total if both parties hire independent counsel, which is strongly recommended. Simple prenuptial agreements for couples with modest assets, straightforward terms, and minimal negotiation typically cost $1,500-$2,500 per party. Complex prenuptial agreements involving business valuations, multiple properties, substantial investments, trusts, and extensive negotiations can cost $3,500-$7,500 or more per party.

Attorney fees typically cover initial consultation to discuss goals and concerns (usually 1-2 hours at $200-$400 per hour), drafting the agreement including multiple revisions based on client feedback (4-8 hours at $200-$400 per hour), reviewing financial disclosures and preparing disclosure schedules (2-4 hours), negotiating terms with the other party's attorney if needed (2-10 hours depending on complexity), and final review and execution meeting (1 hour). Hourly rates for family law attorneys in South Dakota typically range from $200 to $400 per hour depending on location and experience, with Sioux Falls and Rapid City attorneys generally charging higher rates than rural areas.

Online prenuptial agreement platforms have emerged as lower-cost alternatives, with services ranging from $599 to $2,500 depending on the level of attorney involvement and complexity. These platforms typically offer three service tiers: basic DIY templates with no attorney review ($99-$299, not recommended), attorney-reviewed agreements with limited consultation ($599-$999), and full-service agreements with comprehensive attorney involvement ($1,500-$2,500). While online platforms can reduce costs, they may not be suitable for couples with complex assets, business ownership, significant income disparities, or situations where one party may need strong protections.

Additional costs beyond attorney fees may include notarization fees ($5-$25 per signature in South Dakota), professional appraisals for real estate, businesses, or valuable personal property ($300-$5,000 depending on complexity), financial advisor consultation for complex investment portfolios or retirement planning ($200-$500 per hour), and certified copies of the executed agreement for safekeeping ($10-$25 per copy). Couples should budget at least 20-30% above the base attorney fee estimate to account for unexpected revisions, additional negotiations, or complexity that emerges during the drafting process.

The cost of a prenuptial agreement should be weighed against the potential cost of divorce without one. The average divorce in South Dakota costs $8,000-$15,000 for an uncontested case and $15,000-$30,000 or more for a contested case with significant property division disputes. A well-drafted prenuptial agreement can reduce divorce costs by 40-60% by eliminating property division litigation, reducing the length and complexity of divorce proceedings, and providing clear rules that discourage disputes. For couples with substantial assets or complex financial situations, a $5,000 investment in a comprehensive prenuptial agreement could save $20,000-$50,000 in divorce litigation costs.

Enforcement and Modification During Divorce

When a prenuptial agreement is presented during divorce proceedings, South Dakota courts presume the agreement is valid and enforceable under SDCL 25-2-20. The burden of proof falls on the party seeking to avoid enforcement to demonstrate that the agreement was involuntary, or that it was both unconscionable at execution and executed without adequate disclosure. This creates a strong presumption favoring enforcement once the agreement is properly executed, making it difficult to set aside a prenuptial agreement absent clear evidence of defects.

South Dakota courts cannot modify prenuptial agreements based on changed circumstances or fairness considerations at the time of divorce. If the agreement was valid when executed, courts must enforce it according to its terms even if enforcement produces results different from what equitable distribution would provide. For example, if a prenuptial agreement states that each spouse keeps their own retirement accounts and after 20 years one spouse has accumulated $2 million while the other has $100,000, the court must enforce the agreement and allow the disparate result. This differs from some states that allow courts to review prenuptial agreements for fairness at divorce or modify unconscionable provisions.

The only exception to this enforcement rule is that spousal support provisions are automatically void under SDCL 25-2-18 and case law including Sanford v. Sanford. Courts will sever unenforceable alimony provisions while enforcing the remainder of the agreement if the agreement includes a severability clause. If the prenuptial agreement does not include a severability clause, courts will still typically sever the alimony provision rather than void the entire agreement, reasoning that the parties' intent was to address property division primarily and that the property provisions can stand independently.

During divorce proceedings, the court will examine several threshold issues before enforcing a prenuptial agreement. These include whether the agreement is in writing and properly executed with both parties' signatures, whether both parties entered into the agreement voluntarily, whether adequate financial disclosure was provided or properly waived, whether the agreement was unconscionable at the time of execution, and whether the agreement violates public policy (primarily regarding child-related provisions or spousal support). If the challenging party fails to meet their burden of proof on any of these issues, the agreement is enforced according to its terms.

Parties seeking to challenge a prenuptial agreement during divorce should gather evidence demonstrating defects at the time of execution including emails or communications showing coercion, pressure, or limited time to review, evidence that financial disclosure was incomplete or inaccurate, testimony from independent experts about the unconscionability of the agreement's terms, evidence that the challenging party was discouraged from obtaining independent legal counsel, and documents showing the challenging party's lack of financial sophistication or understanding. The challenging party should present this evidence through affidavits, depositions, expert testimony, and documentary evidence during the divorce proceedings, typically through a motion to set aside the prenuptial agreement filed early in the divorce case.

Differences from Postnuptial Agreements

While South Dakota law does not have a separate statutory framework for postnuptial agreements (agreements executed after marriage), courts generally recognize such agreements under common law contract principles and apply similar enforceability standards as prenuptial agreements. The primary legal difference is that postnuptial agreements require independent consideration beyond the marriage itself because the parties are already married when executing the agreement. Consideration means something of value exchanged between the parties such as one spouse's agreement to continue the marriage in exchange for specific property protections, mutual waivers of rights, or other contractual benefits.

Postnuptial agreements may face heightened scrutiny regarding voluntariness because the parties are in an existing marital relationship where one spouse may have greater bargaining power or influence over the other. Courts examine whether the agreement was the product of arms-length negotiation between equals or whether one spouse dominated or took advantage of the other. Factors indicating involuntariness in the postnuptial context include execution during marital crisis when one spouse has leverage due to threatened divorce or separation, significant power imbalances where one spouse controls all finances, lack of independent legal counsel when the agreement is complex or one-sided, and failure to provide adequate time for review and consideration.

The disclosure requirements for postnuptial agreements are similarly strict as for prenuptial agreements. Each party must provide full and fair disclosure of all assets, debts, income, and financial obligations, or the party against whom enforcement is sought must voluntarily and expressly waive disclosure in writing. The unconscionability standard also applies to postnuptial agreements, examining whether the agreement is so one-sided at the time of execution that it shocks the conscience. Postnuptial agreements are subject to the same public policy limitations as prenuptial agreements, meaning they cannot include enforceable spousal support provisions under SDCL 25-2-18 and cannot address child custody or child support.

Postnuptial agreements serve different purposes than prenuptial agreements in several contexts. Common reasons for executing a postnuptial agreement include reconciliation after separation where the parties want to establish clear property rights before reuniting, receipt of a large inheritance by one spouse who wants to keep it separate, starting or acquiring a business during marriage that one spouse wants to protect, significant changes in income or assets that make the original prenuptial agreement outdated or inadequate, and estate planning purposes to clarify how property should be distributed upon death. Postnuptial agreements can be particularly valuable in South Dakota's all-property state context because they allow parties to contractually designate certain property as separate during the marriage rather than waiting until divorce when all property is subject to equitable division.

The timing of execution affects enforceability differently for postnuptial versus prenuptial agreements. While prenuptial agreements presented shortly before a wedding may be involuntary, postnuptial agreements executed during calm periods of the marriage with adequate time for review are more likely to be enforced. However, postnuptial agreements executed during active divorce proceedings or immediately before filing for divorce face significant risk of being set aside as involuntary or lacking consideration because the marriage is effectively ending rather than continuing.

Special Considerations for Business Owners

South Dakota prenuptial agreements are particularly important for business owners because South Dakota's all-property state designation means businesses acquired before marriage or during marriage are subject to equitable division absent a prenuptial agreement. Without a prenup, a family business worth $5 million that one spouse owned before marriage could be divided 40-60% or even 50-50% in a divorce after a long marriage where the non-owner spouse contributed to the marriage in other ways. This creates substantial risk for business owners who want to ensure the business remains under their control and within their family.

Prenuptial agreements protecting business interests should include several key provisions. First, a clear statement that the business is separate property that will not be subject to division in divorce. For example: "The business known as [Business Name] owned by [Party A] as of the date of this agreement, including all appreciation, goodwill, accounts receivable, intellectual property, and other business assets, shall remain the sole and separate property of [Party A] and shall not be subject to division in the event of divorce." Second, provisions addressing business income and whether income generated by the separate business during marriage is separate or marital property, as this can be a contested issue even if the business itself is separate.

Third, valuation procedures for the business if any division is contemplated, including designation of the methodology (asset-based, income-based, or market-based valuation), selection process for business appraisers or valuation experts, timing of valuation (date of separation vs. date of divorce), and treatment of goodwill (personal vs. enterprise goodwill). Fourth, restrictions on the non-owner spouse's involvement in business decisions or operations during marriage and divorce, which can prevent interference with business continuity. Fifth, provisions regarding compensation to the non-owner spouse for contributions to the business such as unpaid labor, business advice, or sacrificing their own career to support the business.

Business owners should obtain professional valuations at the time of executing the prenuptial agreement to establish a baseline value and demonstrate adequate disclosure. This valuation serves multiple purposes: providing the non-owner spouse with full information about the business's worth, establishing a starting point for measuring appreciation during marriage if any portion of appreciation is considered marital, and demonstrating that both parties understood the financial magnitude of the business protection when signing the agreement. Valuations should be updated periodically during marriage, especially if the prenuptial agreement is amended or if the business undergoes significant changes.

Special considerations apply to businesses that grow significantly during marriage. Even if the prenuptial agreement designates the business as separate property, the non-owner spouse may claim entitlement to a portion of the business's appreciation if they contributed to its growth through active involvement, business advice, unpaid labor, or sacrificing their career to allow the owner spouse to focus on the business. Prenuptial agreements should address this scenario by specifying whether appreciation is separate or marital, defining what types of contributions would entitle the non-owner spouse to compensation, and establishing a formula or methodology for calculating any compensation owed. For example, the agreement might state that the business remains separate property but if the non-owner spouse works in the business more than 20 hours per week, they are entitled to reasonable compensation based on market rates for comparable services.

Protection of Inheritances and Family Property

South Dakota's all-property state designation creates particular vulnerability for inheritances and family property in divorce. Unlike most equitable distribution states that exempt inherited property from division, South Dakota courts can divide all property owned during the marriage including inheritances received before or during marriage, family heirlooms and property passed down through generations, and gifts from family members. Prenuptial agreements are essential for protecting these assets and ensuring they remain within the intended family line.

Prenuptial agreements protecting inheritances should include specific language identifying the inheritance or expected inheritance, such as: "Any property inherited by [Party A] from [Party A's] parents [Names] or other family members, whether received before or during the marriage, including real estate, financial assets, personal property, business interests, and any proceeds or appreciation from such inherited property, shall remain the sole and separate property of [Party A] and shall not be subject to division in the event of divorce." The agreement should also address whether income generated by inherited property during marriage is separate or marital, as this can be contested.

For families with significant real estate holdings such as farms, ranches, or family estates, the prenuptial agreement should include detailed legal descriptions of the property, current valuations and appraisals, provisions regarding improvements or enhancements made during marriage (are they separate or marital?), and treatment of income generated by the property during marriage (rental income, agricultural income, etc.). This is particularly important in South Dakota where family farms and ranches often represent multi-generational wealth that families want to preserve within the bloodline.

Inheritances received during marriage present unique challenges even with a prenuptial agreement. The key issue is whether the inherited property remains separate if the non-inheriting spouse contributes to its maintenance, improvement, or appreciation. For example, if one spouse inherits a family farm and the other spouse helps operate the farm for 15 years, does the non-inheriting spouse have a claim to a portion of the farm's value? Prenuptial agreements should address this scenario by clarifying that inherited property remains separate regardless of the non-inheriting spouse's contributions, providing for reasonable compensation to the non-inheriting spouse for documented contributions without giving them an ownership interest, or allowing the inheriting spouse to maintain the property's separate status by ensuring all contributions come from separate property funds.

Waiver of inheritance rights through prenuptial agreements is explicitly permitted under SDCL 29A-2-213. This means parties can contractually agree that upon one spouse's death, the surviving spouse waives all rights to inherit from the deceased spouse's estate including elective share rights, intestate succession rights, and rights to serve as personal representative. Such waivers must be voluntary and not unconscionable at execution. Inheritance waiver provisions are particularly common in second marriages where each spouse wants to ensure their children from prior relationships inherit their estate rather than the new spouse.

Independent Legal Counsel Recommendations

While South Dakota law does not require both parties to have independent legal counsel for a prenuptial agreement to be valid, having separate attorneys for each party is strongly recommended and can significantly strengthen the agreement's enforceability. Courts consider whether both parties had the opportunity to consult independent counsel when evaluating voluntariness and whether adequate disclosure occurred. An agreement where only one party had an attorney faces heightened scrutiny, particularly if the unrepresented party challenges the agreement during divorce proceedings.

Independent counsel serves several critical functions in the prenuptial agreement process. Attorneys explain each provision's legal meaning and implications in plain language, analyze whether the agreement is fair and reasonable under the circumstances, identify potential issues with disclosure, voluntariness, or unconscionability, negotiate terms on behalf of their client to achieve a more balanced agreement, and document the client's understanding and voluntary consent to protect against future challenges. An attorney's involvement creates a record demonstrating that the party understood what they were signing and was not coerced or misled.

The concept of "independent" counsel is important. Each party should have their own attorney who represents only them and has no relationship with the other party or their attorney beyond this matter. Situations that undermine independence include one attorney representing both parties (creating conflicts of interest and likely ethical violations), one party's attorney drafting the agreement for both parties even if the other party consults a different attorney for review only, or attorneys who have close personal or business relationships that could influence their advice. True independence means each attorney zealously advocates for their client's interests and provides candid advice without concern for the other party's preferences.

The unrepresented party should have adequate time and opportunity to retain independent counsel before signing the prenuptial agreement. Best practices include providing the draft agreement to the other party at least 30-45 days before the wedding, explicitly encouraging the other party to consult an attorney and not pressuring them to forgo counsel, offering to contribute toward the other party's reasonable attorney fees (without controlling the attorney selection), and documenting in writing that the party was advised to seek independent counsel. If one party chooses not to hire an attorney after being given adequate opportunity, they should sign a written acknowledgment stating they were advised to seek independent counsel, had adequate opportunity and time to do so, voluntarily chose not to hire an attorney, and understand the legal rights they may be waiving.

Situations where independent counsel is particularly important include significant income or asset disparities between the parties (wealth gap of $500,000 or more), complex financial situations involving businesses, trusts, or multiple properties, agreements that appear one-sided or heavily favor one party, parties with limited financial or legal sophistication, and second marriages involving children from prior relationships. In these scenarios, the absence of independent counsel for both parties substantially increases the risk that a court will find the agreement involuntary or unconscionable if challenged during divorce.

Common Mistakes to Avoid

One of the most common mistakes in South Dakota prenuptial agreements is including spousal support waiver provisions despite SDCL 25-2-18 and case law clearly establishing that such provisions are unenforceable. Many couples use online templates or forms from other states that include alimony waivers, not realizing South Dakota prohibits these provisions. While including an unenforceable alimony clause does not necessarily void the entire agreement if there is a severability clause, it creates confusion and may lead to litigation over which provisions are valid. Attorneys should explicitly advise clients that spousal support cannot be addressed in prenuptial agreements and should omit such provisions entirely or include clear disclaimers.

Another critical mistake is providing inadequate financial disclosure or using vague, generalized disclosure statements. Disclosure stating "Party A has substantial retirement savings" or "Party B owns real estate" is insufficient under SDCL 25-2-20. Proper disclosure requires specific dollar amounts, account numbers, property addresses, valuations, and detailed schedules attached to the agreement. Couples should exchange complete financial statements, tax returns for the past 2-3 years, bank and investment account statements, real estate appraisals, business valuations if applicable, and debt statements. Failing to attach this documentation to the prenuptial agreement or at minimum documenting that it was provided substantially increases the risk of the agreement being set aside.

Presenting the prenuptial agreement too close to the wedding date is a frequent mistake that can result in the agreement being found involuntary. Agreements presented 1-7 days before the wedding face serious enforceability challenges because the non-drafting party has limited ability to negotiate, insufficient time to consult independent counsel, and may feel coerced to sign or cancel the wedding and lose deposits. Courts have found prenuptial agreements involuntary when presented shortly before the wedding even if the parties discussed the general concept earlier. Best practice is to begin prenuptial agreement discussions 3-6 months before the wedding, provide the draft agreement at least 30-60 days before the wedding date, and ensure both parties have adequate time to review, consult counsel, and negotiate terms without pressure.

Failing to address how specific assets will be treated during marriage and upon divorce creates ambiguity that can lead to expensive litigation. Vague provisions like "each party's separate property shall remain separate" are insufficient without defining what constitutes separate property, how appreciation or income from separate property is classified, and what happens if separate and marital property are commingled. Effective prenuptial agreements include detailed provisions for each significant asset category including primary residence, vacation homes and investment properties, retirement accounts and pensions, business interests, bank and investment accounts, vehicles and personal property, and inheritances and gifts. Each category should specify whether it is separate or marital, how it will be divided if at all, and how appreciation or income is treated.

Not updating prenuptial agreements when circumstances change substantially is another common mistake. Prenuptial agreements executed 15-20 years ago may not reflect current assets, income levels, or family situations. While outdated agreements remain enforceable if they were valid when executed, they may not achieve the parties' current objectives. Couples should review and consider amending their prenuptial agreements when they have children (updating estate planning provisions), receive substantial inheritances or gifts, start or sell a business, experience major income changes, acquire valuable real estate, or retire. Amendments must follow the same formalities as the original agreement with written form and signatures by both parties under SDCL 25-2-19.

Finally, many couples make the mistake of treating prenuptial agreement execution as purely transactional without considering the relational impact. Presenting a prenuptial agreement can create feelings of mistrust, hurt, or anxiety about the relationship's future. Successful prenuptial agreement discussions involve open communication about each party's financial goals, concerns, and values, framing the agreement as protecting both parties rather than benefiting only one, discussing the agreement well in advance of wedding planning to avoid pressure, and being willing to negotiate and compromise to reach terms both parties find reasonable. Couples who approach prenuptial agreements collaboratively and transparently are more likely to successfully execute enforceable agreements that strengthen rather than harm their relationship.

Frequently Asked Questions

Are prenuptial agreements enforceable in South Dakota?

Yes, prenuptial agreements are enforceable in South Dakota under the Uniform Premarital Agreement Act (SDCL 25-2-16 through 25-2-25) if they are in writing, signed by both parties, entered into voluntarily, supported by full disclosure or valid waiver, and not unconscionable at execution. However, spousal support provisions are unenforceable per SDCL 25-2-18 and case law.

Can a prenuptial agreement waive alimony in South Dakota?

No, South Dakota is one of the few states that prohibits spousal support waivers in prenuptial agreements. Under SDCL 25-2-18 and controlling case law including Sanford v. Sanford, 694 N.W.2d 283 (2005), any provision attempting to waive, limit, or modify alimony is void and unenforceable as against public policy. Courts retain discretion to award alimony based on circumstances at divorce regardless of prenuptial agreement language.

Does South Dakota require notarization of prenuptial agreements?

No, South Dakota law does not require prenuptial agreements to be notarized for validity under SDCL 25-2-16. However, notarization is strongly recommended by legal practitioners to create a presumption of proper execution, facilitate enforcement, and document that both parties signed voluntarily. South Dakota allows electronic notarization, and notaries must physically witness signatures.

How much does a prenuptial agreement cost in South Dakota?

Prenuptial agreement costs in South Dakota range from $1,500 to $3,500 per party for traditional attorney representation as of March 2026, meaning couples typically pay $3,000 to $7,000 total if both parties hire independent counsel. Simple agreements with straightforward terms cost $1,500-$2,500 per party, while complex agreements involving business valuations and extensive negotiations cost $3,500-$7,500 or more per party. Online platforms offer lower-cost options from $599 to $2,500 depending on attorney involvement.

What happens to property without a prenup in South Dakota?

Without a prenuptial agreement, South Dakota courts divide all property owned during marriage using equitable distribution under SDCL 25-4-44. South Dakota is an all-property state, meaning even premarital assets, inheritances, and gifts are subject to division. Courts divide property fairly (not necessarily equally) based on factors including marriage duration, each spouse's contributions, earning capacity, age, health, and property values. Typical divisions allocate approximately 60-66% to the higher-earning spouse and 33-40% to the lower-earning spouse.

Can prenuptial agreements be changed after marriage in South Dakota?

Yes, prenuptial agreements can be amended or revoked after marriage under SDCL 25-2-19, but only through a written agreement signed by both parties. Oral agreements to modify or revoke have no legal effect. Amendments require no additional consideration beyond mutual consent. Notarization is recommended but not required. Couples should consider amending prenups when significant life changes occur such as having children, receiving inheritances, starting businesses, or experiencing major income changes.

How long before the wedding should I present a prenuptial agreement?

South Dakota courts evaluate voluntariness by examining timing among other factors, and agreements presented shortly before the wedding may be found involuntary. Best practice recommends beginning prenuptial agreement discussions 3-6 months before the wedding and providing the draft agreement at least 30-60 days before the wedding date. This allows adequate time for review, independent counsel consultation, negotiation, and consideration without pressure. Agreements presented 1-7 days before the wedding face serious enforceability challenges.

Does each party need their own attorney for a South Dakota prenup?

South Dakota law does not require both parties to have independent attorneys for a prenuptial agreement to be valid under SDCL 25-2-16. However, having separate counsel for each party is strongly recommended and significantly strengthens enforceability. Courts consider whether both parties had opportunity to consult independent counsel when evaluating voluntariness. Agreements where only one party had an attorney face heightened scrutiny, particularly if challenged during divorce. Independent counsel is especially important when significant wealth disparities exist or terms appear one-sided.

Can a prenuptial agreement protect my business in South Dakota?

Yes, prenuptial agreements can effectively protect business interests in South Dakota by designating the business as separate property that will not be divided in divorce. Protection is particularly important because South Dakota is an all-property state where businesses acquired before or during marriage are subject to equitable division without a prenup. The agreement should specifically identify the business, include current valuations, address how business income and appreciation are treated, and establish valuation procedures if any division is contemplated.

What makes a prenuptial agreement invalid in South Dakota?

A prenuptial agreement is invalid in South Dakota under SDCL 25-2-20 if the challenging party proves it was not voluntary (signed under duress, coercion, or fraud), OR proves both that it was unconscionable when executed AND they were not provided fair financial disclosure, did not waive disclosure in writing, and could not reasonably have known the other party's finances. Additionally, provisions regarding spousal support, child custody, and child support are automatically unenforceable per SDCL 25-2-18 and public policy.

Author: Antonio G. Jimenez, Esq. | Florida Bar No. 21022

Legal Disclaimer: This guide provides general information about South Dakota prenuptial agreement laws and should not be construed as legal advice. Prenuptial agreement law involves complex statutory interpretation, case law application, and fact-specific analysis. Consult a licensed South Dakota family law attorney before executing a prenuptial agreement to ensure it meets statutory requirements and achieves your objectives.

Sources:

• South Dakota Codified Laws Title 25, Chapter 2
• South Dakota Premarital Agreements - HelloPrenup
• South Dakota Prenup Laws | Trusted Prenup
• South Dakota Marital Property Laws - FindLaw
• Sanford v. Sanford, 694 N.W.2d 283 (S.D. 2005)