Annulment in Montana: Grounds, Filing, and Deadlines

An annulment in Montana — formally called a declaration of invalidity — is available when a marriage was defective from the moment it began, not simply because it failed later. A district court can declare the marriage invalid under Montana Code 40-1-402 if one of the specific statutory grounds existed at the time of the wedding and you file within the deadline that applies to that ground.¹ Unlike a divorce, which ends a valid marriage going forward, an annulment treats the marriage as though it should never have existed. That difference reaches property division, parenthood, and immigration status, so it pays to understand what qualifies and what the decree actually does before you file.

Who Qualifies for an Annulment

Montana law recognizes two categories of invalid marriages. Voidable marriages are valid until a court says otherwise; prohibited marriages are barred outright.

Voidable Grounds

A marriage is voidable if, at the time of the ceremony, any of the following was true:¹

One spouse lacked the mental capacity to consent, whether because of a mental condition or because they were under the influence of alcohol, drugs, or another incapacitating substance.
One spouse was forced, pressured, or defrauded into marrying. The fraud has to go to something fundamental about the marriage itself; a lie about something minor won’t do it.
One spouse was physically unable to consummate the marriage and the other spouse didn’t know before the wedding.
One party was under 16, or was 16 or 17 without the required parental consent or judicial approval.

Prohibited Marriages

Some marriages are categorically off-limits. A marriage entered into while one spouse was still legally married to someone else is prohibited, as are marriages between a parent and child, siblings of full or half blood, an uncle and niece, or an aunt and nephew.² For these, either spouse, the earlier legal spouse in a bigamy situation, a county attorney, or a child of either party can seek invalidation at any point before one of the spouses dies.¹

Deadlines You Cannot Miss

Miss the deadline and your only remaining option is divorce. No annulment can be sought after either spouse has died, and each voidable ground has its own filing window that starts running when you learn of the problem, not on the wedding day.¹

Mental incapacity or influence of alcohol or drugs: one year from when you learned of the condition.
Force, duress, or fraud: two years from when you learned of the problem.
Inability to consummate: four years from when you learned of the condition.
Underage marriage: before the underage spouse reaches the age at which they could have legally married without whatever was missing — parental consent or judicial approval.
Prohibited marriage: no deadline; any time before either spouse dies.

Discover fraud six months into the marriage and you have two years from that point. Sit on the knowledge past the window and the court will not carve out an exception.

How to File in Montana

You file in the district court of the county where you or your spouse lives. The filing fee is $120, and a Statement of Inability to Pay Court Costs and Fees is available if you cannot afford it.³⁴

The Montana Judicial Branch provides standardized forms. To open the case you complete and file three sets of the following with the Clerk of District Court:⁴

Petition for Declaration of Invalidity of Marriage (MP 120), which identifies the parties, states your grounds, and lays out what you’re asking the court to decide.
Summons and Automatic Economic Restraining Order (MP 420), which notifies your spouse and imposes immediate financial restrictions on both of you.
Request for Sheriff to Serve Documents (MP 421), only if you want the sheriff’s office rather than a private process server to deliver the papers.

Once served, your spouse has a set window to respond. If they don’t, you can request a default judgment. If they contest, the case proceeds to a hearing where the judge decides whether the statutory grounds have been met. To get that hearing scheduled you file a second set of forms — a Request for Entry of Default (if applicable), a Request for a Hearing, a proposed Order for Hearing, and a proposed Declaration of Invalidity of Marriage.⁴ Procedures vary by judicial district, so ask the local Clerk of District Court about any specific requirements.

The moment you file, an automatic economic restraining order takes effect for both spouses. Neither of you can transfer, hide, or dispose of marital property without written consent or a court order, cancel health or auto insurance covering either spouse or the children, change life insurance beneficiaries, or borrow against life insurance cash value. Ordinary living expenses, normal business operations, and legal fees are still allowed.⁵ Violating the order can lead to contempt of court.

Retroactive or Non-Retroactive: A Distinction That Matters

By default, a Montana court declares the marriage invalid as of the original wedding date, meaning it’s treated as if it never happened.¹ The court can instead enter a non-retroactive decree if it finds that erasing the marriage from day one would be unfair to a spouse or to third parties like creditors or children.

The difference reaches financial remedies. A non-retroactive decree brings the full range of divorce-style protections in Chapter 4 of Montana’s family law code, including property division, spousal maintenance, and child support and parenting provisions.¹ A retroactive decree doesn’t explicitly carry all of the same protections in the statute, though the property division statute itself references declarations of invalidity in its text.⁶ If you have significant shared assets or need spousal support, raise the retroactive-versus-non-retroactive question with an attorney before the hearing.

What Happens to Property and Support

A common misconception is that annulment leaves the court powerless over marital property. It does not. Montana’s property division statute, Montana Code 40-4-202, expressly covers declarations of invalidity alongside dissolutions and legal separations. Each spouse has a common ownership interest in the marital property that vests immediately before the decree is entered.⁶

The court divides the marital estate equitably, considering the duration of the marriage, each spouse’s economic circumstances, and contributions to jointly acquired property. The division is not treated as a sale or transfer for state or federal income tax purposes.⁶ Because annulled marriages are often short, there is frequently less to divide than in a typical divorce.

Spousal maintenance is available in non-retroactive annulment decrees through Chapter 4. A spouse asking for maintenance must show they lack sufficient property to cover reasonable needs and cannot become self-supporting through appropriate employment.⁷ Awards in these short-marriage cases tend to be uncommon, but the option is on the table when circumstances warrant it.

Children Are Not Erased

Children born during a marriage later declared invalid are legitimate under the statute.¹ Montana’s paternity presumption reinforces the point: a person is presumed to be the father of a child born during the marriage or within 300 days after the marriage is terminated by annulment.⁸

The court retains full authority to decide custody, parenting plans, and child support just as it would in a divorce, and those decisions turn on the best interests of the child. Neither parent can escape a support obligation by arguing the marriage was invalid. If children are involved, expect parenting and support to be handled in the same proceeding.

When Divorce Is the Better Fit

Annulment is narrower than divorce in every respect. You can’t get one just because the marriage failed. You need to prove one of the statutory grounds existed when you married, and you need to file within the deadline. If neither is true, divorce is the route.

The distinction also matters beyond the courthouse. Some people want an annulment for personal or religious reasons because it produces a different legal status: not a divorced person, but someone whose marriage was never valid. For others, that same result creates problems. If you are a foreign-born spouse whose immigration status is tied to the marriage, treating the marriage as though it never existed can create serious complications for a green card or conditional residence that a divorce would not. Weigh that carefully before choosing an annulment over a dissolution.

1
Montana State Legislature. Montana Code 40-1-402 – Declaration of Invalidity
2
Montana State Legislature. Montana Code 40-1-401 – Prohibited Marriages Contracts
3
Montana Judicial Branch. Fee Schedule – Civil Montana Clerks of District Courts
4
Montana Judicial Branch. How to File for Declaration of Invalidity of Marriage
5
Montana State Legislature. Montana Code 40-4-126 – Automatic Economic Restraining Order
6
Montana State Legislature. Montana Code 40-4-202 – Division of Property
7
Montana State Legislature. Montana Code 40-4-203 – Maintenance
8
Montana State Legislature. Montana Code 40-6-105 – Presumption of Paternity