Montana Prenuptial Agreement
Montana prenuptial agreements are governed by MCA §§ 40-2-601 to 40-2-610. Challengers must prove either involuntary execution, OR unconscionability at signing plus all three of inadequate disclosure, no written waiver of disclosure, and lack of financial knowledge. Unconscionability alone is not enough. Spousal support waivers are enforceable with a minimum of public assistance eligibility.
Bottom line: Montana earns an A grade. UPAA consistency, execution-only unconscionability review with no second look at divorce, a tough conjunctive challenge standard, and a narrow alimony floor at public assistance eligibility give Montana prenups more certainty than most other states.
Montana Prenup Enforceability Rating: A
Montana Prenup Laws: Key Statutes Explained
Montana Uniform Premarital Agreement Act, codified at Mont. Code Ann. §§ 40-2-601 through 40-2-610
Separate Property
All assets can remain separate property, avoiding costly divorce settlements. Joint assets and debts titled in both names can be split 50/50 according to a prenuptial agreement.
Unconscionability Single Review (Pro-Prenup)
Montana reviews prenuptial agreements for unconscionability ONLY at execution (signing), not at enforcement (divorce). This prevents courts from second-guessing agreements based on changed circumstances during marriage, providing greater certainty and discouraging litigation challenges.
Unconscionability Standard—MCA § 40-2-608 Two-Prong Test
A prenup is unenforceable if the challenging party proves: (1) involuntary execution due to coercion or undue pressure; OR (2) the agreement was unconscionable at execution AND (a) lacked fair and reasonable disclosure of the other's property/obligations, (b) no written waiver of disclosure, AND (c) challenging party lacked adequate knowledge of the other's finances.
Spousal Support Public Assistance Minimum
Courts may override spousal support waivers if enforcement would make one party eligible for public assistance at separation or divorce. However, courts can only require support "to the extent necessary to avoid that eligibility" under MCA § 40-2-608(2).
Timing
No minimum specified, but we recommend signing the prenup 60+ days before the wedding, with both parties having 2-3 weeks to review the final version to minimize challenge risk. Reach out to an attorney at least 4-6 months before the wedding with your draft prenup. Better yet, sign the prenup before proposing.
Independent Counsel
Not required (Wilkes upheld a prenup where one spouse had no counsel), but separate counsel dramatically strengthens enforceability if the agreement is later challenged. Montana courts weigh independent legal review heavily in voluntariness analysis.
Financial Disclosure
"Fair and reasonable disclosure" of property and financial obligations required under MCA § 40-2-608, or written waiver. PerfectPrenup includes both. Schedules must accurately reflect property owned at signing — listing assets not yet acquired risks invalidation (Shiffman).
Moderate Burden to Challenge
Challenging party must prove either involuntary execution or unconscionability plus lack of disclosure. Montana courts enforce PMAs as written under standard contract principles, with unconscionability decided as a matter of law by the court — not the jury.
Child Support and Custody
Child support and custody clauses are unenforceable and could undermine the entire agreement. Do not include.
Montana Prenuptial Agreement Court Cases
In re Marriage of Shirilla, 2004 MT 28, 319 Mont. 385, 89 P.3d 1
The Montana Supreme Court invalidated a PMA between a Butte physician and his Russian fiancée — who spoke limited English, was facing visa expiration, and had given up her home and job in Russia — holding that the combination of language barriers, immigration-timing pressure, and token contractual maintenance ($5,000 if divorce <2 years, $7,500 if >2 years) rendered her execution involuntary under § 40-2-608(1)(a), and the court awarded her $1,000/month maintenance for 20 months after invalidation.
In re Marriage of Shiffman, 2023 MT 5N
In a noncitable memorandum opinion, the Court affirmed invalidation of an alleged PMA from a 1998 marriage on both involuntariness and unconscionability grounds because the wife had no independent counsel, denied signing, the schedule listed property she did not acquire until years later (sewing machine, computer, "Cabin C" not yet built), and the supposed drafting attorney could not recall preparing the document.
In re Marriage of Stout/Gollehon, 261 Mont. 10, 861 P.2d 856 (1993)
Montana's first post-UPAA enforcement decision held that a wife's later regret about her husband's post-marital conduct (terminating a lease) did not render her original execution involuntary, establishing that "voluntariness" under § 40-2-608(1)(a) is judged at the time of signing based on then-existing circumstances.
Wilkes v. Estate of Wilkes, 2001 MT 118, 305 Mont. 335, 27 P.3d 433
The Court enforced a PMA signed two days before the wedding by a 21-year-old developmentally disabled wife who had no independent counsel against a 62-year-old husband in poor health, holding that capacity and unconscionability challenges failed where the wife was mentally competent to understand the agreement and the husband had a legitimate purpose (preserving assets for his three children from a prior marriage).
In re Marriage of Hutchins, 2018 MT 286, 393 Mont. 530, 432 P.3d 184
The Court enforced a PMA signed one week before the parties' Las Vegas wedding using a single shared attorney, applying Nevada law under the agreement's choice-of-law clause, and held that the homemaker wife was barred from claiming any premarital portion of her physician husband's Nevada PERS retirement account (the largest marital asset) because the PMA's clean maintenance waiver foreclosed using property division as a back-door alimony substitute.
Sayler v. Yan Sun, 2023 MT 175, 413 Mont. 303, 536 P.3d 399
In a surrogacy-plus-PMA case, the Court enforced the premarital agreement against the father's argument that the surrogate had "effectively" represented the PMA was necessary to get married, reaffirming that absent express misrepresentation, incapacity, fraud, or duress, ignorance or disregard of clear contract language is no defense to enforcement.
5-Step Checklist: How to Sign & Execute a Prenup in Montana
Step 1: Download and read the Montana prenuptial agreement
Start with our free template. It is written for Montana-specific statutes and case law under MCA §§ 40-2-601 to 40-2-610 (Uniform Premarital Agreement Act). Read it in full — know what you are getting into legally with marriage. The 15+ pages is written thoroughly to include rebuttals to common legal challenges and fallback provisions.
Step 2: Draft changes on your own
See a clause you don't like? Copy it into an AI like Claude, explain what you'd like to change or what you want the clause "to do." Save any changes as a separate alternate version — don't overwrite the original. Bring both versions to your attorney review. Note: AI is often gender-biased and crafts terms beyond what is legally required. Push back on its output.
Step 3: Find a matrimonial or divorce lawyer in Montana
Find a matrimonial or divorce attorney in your state. Avvo, Findlaw, and Justia are good. Look for someone with 10+ years experience. Call or email and ask them how much to review your draft prenup and help with signing. Send them your draft.
Step 4: Meet your lawyer 4–6 months before the wedding
Our recommendation: sign the prenup before proposing. That way, you both get the legal work out of the way, and you know this is the right person to marry. Already proposed? 4–6 months before the wedding should leave you enough time to give your spouse 1–2 weeks to review the final draft and have it signed 60+ days before the wedding. Montana has upheld prenups signed just days before the wedding (Wilkes — 2 days; Hutchins — 1 week), but rushed signings combined with language barriers, missing counsel, or visa pressure are the most successful challenge grounds (Shirilla).
Step 5: Review and sign the prenup with your attorney
Both attorneys present can serve as witnesses and notarize on the spot, satisfying all requirements in one signing ceremony. We HIGHLY recommend having the prenup reviewed and signed with an attorney, however, if you don't have an attorney, you at least need the signatures to be notarized. Each party keeps a signed original, and so should each party's attorney.
Montana Prenuptial Agreement: Frequently Asked Questions (2026)
1. Are prenups legal in Montana?
Yes. Montana enforces prenuptial agreements under the Uniform Premarital Agreement Act, MCA §§ 40-2-601 to 40-2-610, enacted in 1987. A prenup is enforceable if it is in writing, signed by both parties before marriage, and signed voluntarily — and it cannot be invalidated based on changed circumstances during the marriage.
2. How much does a prenup cost in Montana?
Attorney-drafted prenups typically cost $1,200 to $2,400 for straightforward agreements and up to $10,000 for complex situations involving businesses, ranches, or trusts. Single-attorney drafting can run $600 to $800. The national average is roughly $8,000 per couple. Online platforms like PerfectPrenup are dramatically cheaper.
3. Does a Montana prenup need to be notarized?
No. MCA § 40-2-604 requires only that the agreement be in writing and signed by both parties — notarization and witnesses are not statutory requirements. However, notarization is strongly recommended to prove authenticity and defeat later claims that a signature was forged or coerced (see Shiffman, where a wife successfully denied signing).
4. Do you need a lawyer for a prenup in Montana?
No. Montana has explicitly enforced prenups where one spouse had no independent counsel (Wilkes, 2001). However, separate attorneys for each party significantly strengthen enforceability and are weighed heavily in voluntariness analysis. Hutchins (2018) upheld a prenup with one shared attorney; Shirilla (2004) struck one down where the lower-earning spouse had no counsel and faced visa pressure.
5. What can you include in a Montana prenup?
Under MCA § 40-2-605, parties can contract on: property rights and obligations, asset management during marriage, division on divorce or death, spousal support modification or elimination, wills and trusts, life insurance proceeds, and choice of governing law. Anything not violating Montana public policy or criminal law is permitted.
6. What can't you include in a Montana prenup?
Child support and child custody cannot be predetermined — MCA § 40-2-605(2) provides that a child's right to support cannot be adversely affected by a prenup, and custody is decided by the court at divorce based on the child's best interests. Including these provisions risks invalidating surrounding clauses.
7. Can you waive alimony in a Montana prenup?
Yes. MCA § 40-2-605(1)(d) expressly allows modification or elimination of spousal support. The only exception is MCA § 40-2-608(2): if the waiver would leave one party eligible for public assistance at separation, a court can require limited support — but only "to the extent necessary to avoid that eligibility."
8. How long before the wedding should you sign a prenup in Montana?
Montana has no statutory minimum. The Montana Supreme Court has upheld prenups signed two days before the wedding (Wilkes) and one week before (Hutchins). However, signing 60+ days before the wedding with 2-3 weeks of review time is recommended. Last-minute signings combined with language barriers, missing counsel, or coercion are the most successful challenge grounds (Shirilla).
9. Can a Montana prenup be challenged or overturned?
Yes, but the burden is on the challenger. Under MCA § 40-2-608, a prenup is unenforceable only if the challenging party proves either (1) involuntary execution, or (2) unconscionability at signing combined with all three of: no fair financial disclosure, no written waiver of disclosure, AND no reasonable knowledge of the other's finances. Unconscionability is decided by the judge as a matter of law — not by a jury.
10. Does a Montana prenup protect inherited property?
Yes, but it requires explicit drafting. Montana follows an "all-property" equitable distribution approach under MCA § 40-4-202, meaning courts can divide premarital and inherited assets without a prenup. A properly drafted prenup overrides this default and keeps inheritances and premarital assets separate. Avoid commingling — the Montana Supreme Court has held that commingled separate property becomes marital.
11. How do you change or revoke a Montana prenup after marriage?
Under MCA § 40-2-607, a prenup can only be amended or revoked by a written agreement signed by both parties — oral modifications are unenforceable. The amendment is enforceable without consideration. This is sometimes called a postnuptial agreement.
12. Does Montana recognize common law marriage, and does it affect prenups?
Yes. Montana is one of the few states that still recognizes common law marriage under MCA § 40-1-403. Couples cohabiting and holding themselves out as married can become legally married without a ceremony — at which point any prior prenup signed "in contemplation of marriage" takes effect under MCA § 40-2-606. If you're cohabiting in Montana and want financial separation, sign a prenup before holding yourselves out as a couple.