What Makes a Prenup Invalid in Wyoming? Understanding Enforceability Requirements
You spent months negotiating your prenuptial agreement. You and your spouse fully disclosed your finances, you both had attorneys, you signed it well before the wedding. Now you're divorcing, and your ex is challenging the prenup, claiming it's invalid.
Can a prenup be thrown out? Yes. Wyoming courts can refuse to enforce prenuptial agreements that violate legal requirements or public policy. Understanding what makes a prenup invalid helps you avoid creating an unenforceable agreement.
Wyoming's Legal Framework: Contract Law, Not a Uniform Act
Wyoming has never adopted the Uniform Premarital Agreement Act, and no Wyoming statute sets out a test for prenups. They are governed by the common law of contracts as the Wyoming Supreme Court has developed it: a premarital agreement is valid and enforceable and is read under the same rules of construction that apply to any other contract, a rule the court applied again when it enforced an agreement exactly as written in Morrison v. Hinson-Morrison, 2024 WY 96, and in Jones v. Young, 2025 WY 130. Three consequences follow. A prenup can be attacked only on the grounds available against any contract: it was not signed voluntarily (duress, coercion, fraud), it was procured by concealment of the finances it was meant to allocate, or its terms were unconscionable when it was made. A postnuptial agreement needs something more, because once the marriage exists it cannot serve as the consideration; there must be an exchange of other identifiable consideration (Combs v. Sherry-Combs, 865 P.2d 50 (Wyo. 1993); Long v. Long, 2018 WY 26). And a provision that tries to decide custody or cap child support is void as against public policy whatever the rest of the agreement says (Combs). The sections below take those grounds one at a time.
Let's break down each of these grounds for challenging a prenup.
Involuntary Execution: Signing Under Duress or Coercion
For a prenup to be enforceable, both parties must sign voluntarily—without duress, coercion, fraud, or undue pressure. But what counts as "involuntary"?
Timing is a major factor. If you present your fiancé with a prenup three days before the wedding, when 200 guests have confirmed attendance, non-refundable deposits have been paid, family has traveled from across the country, and the venue is booked, that's coercive. Your fiancé can't realistically say no without canceling the wedding and humiliating both families.
Wyoming courts look at whether the spouse who didn't want the prenup had a realistic opportunity to refuse. If the practical and social pressure to go through with the wedding was so great that they couldn't freely choose to walk away, the agreement might be involuntary.
This is why attorneys recommend executing prenups at least 30-60 days before the wedding. This timeline demonstrates that both parties had adequate time to review the agreement, consult with attorneys, negotiate terms, and make changes. It shows the agreement was voluntary, not coerced by wedding pressure.
Other factors suggesting involuntary execution include:
- Threats or ultimatums ("Sign this or I'll call off the wedding")
- Emotional manipulation or pressure
- Taking advantage of illness, grief, or vulnerability
- Fraud or misrepresentation about what the agreement contains
- One party being intoxicated or mentally incapacitated when signing
If your ex can prove they signed under any of these circumstances, the prenup may be invalid.
Unconscionability: Grossly Unfair Terms
Even if a prenup was signed voluntarily with full disclosure, it can still be invalidated if it's unconscionable—meaning so unfairly one-sided that it shocks the conscience.
This is a high bar. It's not enough that the agreement is merely unfavorable or that one party got a better deal. The terms must be extraordinarily unjust, with one party receiving essentially nothing while the other keeps everything.
For example, a prenup that gives a spouse who sacrificed their career to raise children and support their partner's business absolutely nothing after 20 years of marriage might be unconscionable. Or an agreement that waives all alimony for a spouse who will have no means of support after divorce.
Wyoming's cases test the agreement as of when it was made: whether it was entered knowingly and willingly, free of fraud and duress, and whether its terms were unconscionable then. A prenup that was fair when signed is not undone because it looks improvident fifteen years later, and the Supreme Court has refused to supply terms the parties left out of the document. Changed circumstances are a reason to amend the agreement while the marriage is intact, not a defense at divorce.
Lack of Financial Disclosure
Full financial disclosure is critical to prenup enforceability. Both parties must disclose their assets, debts, income, and financial obligations before signing.
If one spouse hides assets or provides incomplete financial information, the other spouse can challenge the prenup on grounds they didn't have adequate information to make an informed decision.
For example, if your fiancé tells you they have $100,000 in assets but actually has $2 million, and you agreed to terms based on the false $100,000 figure, you can challenge the agreement. You didn't know what you were waiving rights to because your fiancé concealed their true financial situation.
This is why attorneys require detailed financial disclosures with supporting documentation—tax returns, bank statements, investment account statements, business valuations, property appraisals, and debt statements. This creates a clear record showing both parties had full information when they signed.
The disclosure must be "fair and reasonable"—meaning sufficient to give the other party a general understanding of your financial situation. You don't need to list every bank transaction, but you do need to disclose all significant assets and debts.
Wyoming has no statutory rule that a written waiver of disclosure cures the absence of it. The schedules of assets and debts attached to the agreement are what prove the disclosure was made; a recital that disclosure was waived is only evidence, and a court will still ask whether the spouse knew what was being given up.
Including Prohibited Provisions
Some provisions are prohibited in Wyoming prenups, and including them can invalidate the entire agreement or just those specific provisions.
Child Support and Custody: You cannot include provisions determining child custody or limiting child support. These decisions are made by courts based on the child's best interests at the time of divorce, not based on agreements made years earlier.
If your prenup includes custody or child support provisions, those sections are void. This usually doesn't invalidate the entire agreement—just the prohibited provisions—but it creates ambiguity and potential challenges.
Provisions Encouraging Divorce: Any clause that incentivizes divorce is void as against public policy. For example, a provision giving one spouse a large payment if the marriage ends before five years essentially creates a financial incentive to divorce. Courts won't enforce this.
Criminal Provisions: You can't include provisions that involve criminal activity, violate public policy, or attempt to contract away non-financial rights (like religious upbringing of children, personal behavior, or intimate relations).
No Written Agreement
This seems obvious, but prenups must be in writing and signed by both parties. Oral agreements are completely unenforceable, even if you both agreed to terms and relied on them.
The requirement protects both parties by ensuring there's no dispute about what was agreed to. Everything is in black and white, signed and (ideally) notarized.
Failure to Become Effective
Prenuptial agreements become effective upon marriage. If you sign a prenup but never actually get married, it doesn't become enforceable.
This occasionally creates issues with couples who live together for years after signing a prenup but never formally marry. The prenup isn't effective, and the couple has no legal protections despite believing they do.
Both Parties Represented by the Same Attorney
While Wyoming doesn't require both parties to have independent legal counsel, having one attorney represent both parties creates serious problems.
An attorney cannot effectively represent both sides when they have conflicting interests. An attorney cannot simultaneously advocate for terms that protect you while also advocating for terms that protect your fiancé when those interests conflict.
If both parties are represented by the same attorney and the prenup is later challenged, courts look skeptically at whether both parties truly understood the agreement and received adequate legal advice.
Attorneys always recommend both parties have their own attorneys. This protects everyone and makes the agreement much harder to challenge later.
How to Create an Enforceable Prenup
To avoid these pitfalls:
- Execute the agreement at least 30-60 days before your wedding
- Provide complete financial disclosure with supporting documentation
- Both parties should retain independent legal counsel
- Ensure terms are fair and not grossly one-sided
- Don't include provisions about child custody or child support
- Have the agreement notarized
- Keep the signed original in a safe place
What Happens If a Prenup is Invalid?
If a court determines your prenup is invalid, Wyoming's default property division laws apply. The court will divide marital property according to equitable division principles, considering factors like:
- Length of the marriage
- Each spouse's income and earning capacity
- Contributions to marital property
- Age and health of each spouse
- Custody arrangements
This might result in a very different outcome than what your prenup specified. This is why getting it right the first time is critical.
Reviewing and Updating Your Prenup
Even a valid prenup can become outdated as circumstances change. You might want to review your agreement if:
- You have children
- One spouse receives a large inheritance
- You start a business
- One spouse's income changes significantly
- You move to a different state
You can create a postnuptial agreement to modify the terms of your prenup or replace it entirely. The same requirements apply—written, signed, voluntary, full disclosure, fair terms—plus one more: because the marriage already exists, it cannot serve as the consideration, so each spouse has to give something identifiable in exchange (Combs v. Sherry-Combs, 1993).
Get It Right From the Start
The best way to ensure your prenup will be enforced is to work with an experienced Wyoming attorney who understands the state's requirements. Don't use online templates or try to draft the agreement yourself. The money you save isn't worth the risk of having an unenforceable agreement.
