Prenuptial Agreements in Michigan: What They Cover and How to Make One Enforceable

Prenuptial agreements have lost most of their stigma — and for good reason. A well-drafted prenup isn't a prediction that a marriage will fail. It's a financial planning tool that protects both parties, prevents disputes, and ensures that both spouses enter the marriage with clear expectations. For clients in Oakland County and Southeast Michigan with significant assets, a business, or prior family obligations, a prenup is often the responsible choice.

Michigan Governs Prenups Under Common Law, Not the UPAA

This is one of the most important things to understand about Michigan prenuptial agreements: Michigan has not adopted the Uniform Premarital Agreement Act, which has been enacted in the majority of states. There is no comprehensive prenuptial agreement statute in Michigan that sets out a specific list of requirements.

Instead, Michigan prenuptial agreements are governed primarily by common law — court decisions developed over time. MCL 557.28 expressly authorizes premarital contracts, providing that a woman may make contracts before marriage that remain binding after, but it does not establish the enforceability framework. That framework comes from case law, most importantly Rinvelt v Rinvelt, 190 Mich App 372 (1991), and subsequent Michigan appellate decisions.

This matters practically because there is no statutory safe harbor to point to. Enforceability is fact-specific and highly dependent on the circumstances of the signing — which is exactly why the drafting and execution process requires experienced family law counsel.

What a Michigan Prenuptial Agreement Can Do

Michigan courts have consistently upheld prenups that address financial matters between the parties, including:

• Separate property protection — defining which assets each spouse brings into the marriage and keeping them separate throughout
• Business ownership — protecting a professional practice, family business, or ownership interest from being treated as marital property
• Debt allocation — specifying that each spouse remains responsible for their own pre-marital debt and keeping it separate from the marital estate
• Spousal support — waiving the right to alimony, capping it at a set amount, or defining duration
• Inheritance protection — ensuring that assets intended for children from a prior relationship are preserved and not subject to division
• Investment accounts and retirement funds — clarifying which portions of retirement accounts are separate vs. marital property

What a Prenuptial Agreement Cannot Do

Michigan courts will not enforce prenuptial provisions that:

• Determine child custody or child support — these are always decided by the court at the time of divorce based on the child's best interests, and no pre-marriage contract can override that
• Waive rights that arise from criminal conduct by one spouse
• Include incentives to divorce or provisions contrary to public policy
• Waive rights to marital property in a way that was unconscionably one-sided at the time of execution

What Makes a Michigan Prenup Enforceable: The Legal Framework

Because Michigan has not adopted the UPAA, there is no checklist statute to follow. Enforceability is governed by principles developed across decades of Michigan appellate decisions. Two cases anchor the framework.

Rinvelt v Rinvelt, 190 Mich App 372 (1991) is the foundational Michigan case on prenuptial agreement enforceability. The Court of Appeals held that an antenuptial contract will be enforced unless it was obtained by fraud, duress, mistake, or misrepresentation; is unconscionable; or is contrary to public policy. The court also emphasized that both parties must have entered the agreement voluntarily and with an understanding of what rights they were surrendering — which requires, at minimum, that each party knew the general nature and extent of the other's property.

Allard v Allard establishes a critical limitation that many attorneys who handle prenuptial agreements infrequently do not fully appreciate — and that limitation directly affects how a Michigan prenup must be drafted to be durable. The Allard court held that parties to a prenuptial agreement cannot waive the court's statutory power to reach into what would otherwise be separate property in order to create equity between the spouses. Michigan statutes give courts this equitable power expressly — it is a judicial tool that exists to prevent fundamentally unjust outcomes, and the Allard court held that the parties themselves cannot contract around it.

The practical consequence is significant. A prenuptial agreement that purports to place certain assets entirely beyond the court's reach — to permanently and unconditionally ring-fence separate property from any equitable consideration — may not be fully enforceable as written, regardless of how clearly the intent is expressed. Courts retain the power to look at the overall fairness of the situation and, in appropriate circumstances, invade property that the parties agreed to keep separate. An attorney who drafts a prenup with language suggesting absolute and irrevocable protection of separate property, without accounting for this doctrine, has created a false sense of security.

This is exactly the kind of nuance that separates experienced prenuptial agreement counsel from those for whom prenups are not a core part of their practice. At Dizik Kaplan, we draft Michigan prenuptial agreements with Allard in mind — building in the provisions and disclosures that give the agreement the best possible chance of surviving challenge under both Rinvelt and Allard, rather than drafting around a body of law the attorney doesn't know.

From these cases, the enforceability requirements that matter most in practice are:

1. The agreement must be in writing. An oral prenuptial agreement is not enforceable in Michigan. The agreement must be a signed, written contract. This is not just a formality — the writing requirement ensures that both parties have a clear, unambiguous record of what they agreed to, and protects against later disputes about what was and wasn't included.

2. Full and fair disclosure of assets and debts. Before signing, each party must disclose — or have reasonable knowledge of — the other's financial situation: assets, income, debts, liabilities, and any other material financial obligations. This does not require a forensic accounting exercise, but it does require honesty. Disclosure should be documented in the agreement itself or in a separate exhibit listing each party's financial profile. Courts have voided agreements where one spouse had a substantially larger estate than disclosed, or where significant debts were omitted.

3. Voluntary execution — no fraud, duress, or misrepresentation. The agreement must have been entered freely. An agreement presented for the first time the night before the wedding — with the venue booked, guests flying in, and deposits already paid — is exactly the kind of circumstance courts scrutinize for duress. The closer to the wedding date, the greater the risk a future challenge succeeds on this ground.

4. Not unconscionable at execution. The terms must not have been fundamentally one-sided at the time of signing. Courts evaluate fairness as of the date of execution, not what the agreement looks like years later. That said, a provision that was technically fair at signing but leaves one spouse with nothing after a long marriage can still come under significant scrutiny in some circumstances.

Whether both parties had a genuine opportunity to consult independent legal counsel runs through all of these factors. Michigan law does not require separate attorneys, but signing without the chance to seek advice is a significant vulnerability. It bears directly on voluntariness, on whether the party truly understood the agreement, and on whether the disclosure was meaningful. We strongly advise that both parties retain their own counsel before signing.

Timing: When to Start the Process

Start early. As a practical rule, initiate the prenup conversation and drafting process three to six months before the wedding. Both attorneys need time to review, negotiate, and finalize — and both parties need time to actually read and understand what they're agreeing to. An agreement executed with adequate lead time and documented opportunity for independent review is far more durable than one rushed to signature in the weeks before the ceremony.

In our Oakland County practice, we regularly work with both parties' counsel simultaneously to ensure the agreement is genuinely mutual, that disclosure is documented, and that the execution process is recorded in a way that will hold up if the agreement is challenged years later.

Postnuptial Agreements

If you're already married and want to document a financial arrangement with your spouse, a postnuptial agreement is the appropriate vehicle. Michigan courts recognize postnuptial agreements, but apply heightened scrutiny — the circumstances of a marriage create greater potential for coercion and unfair pressure than the circumstances of an engagement. Voluntary execution, full financial disclosure, and independent counsel are even more important in the postnuptial context.

Frequently Asked Questions About Michigan Prenuptial Agreements