No. Montana does not require you to separate before you file for divorce. The 180-day separation that people read about is one of two ways to show that a marriage is irretrievably broken, and the other way requires no time apart. This page explains both and clears up the difference between that rule and a waiting period. It is part of our Montana Divorce Guide.

Where the 180 Days Comes From

Before a Montana court enters a decree of dissolution (the statutory term for divorce), it must find that the marriage is irretrievably broken. Under MCA § 40-4-104(1)(b), that finding must be supported by evidence:

  • that the spouses "have lived separate and apart for a period of more than 180 days preceding the commencement of this proceeding," or
  • that "there is serious marital discord that adversely affects the attitude of one or both of the parties towards the marriage."

Either one is enough. The 180 days is a kind of proof, not a hurdle everyone must clear. The petition tracks the same choice: it states that the marriage is irretrievably broken in that "either" the spouses have lived apart for more than 180 days or there is serious marital discord and no reasonable prospect of reconciliation (MCA § 40-4-105(1)(c)).

Separation Is Evidence, Not a Waiting Period

People often expect a mandatory separation period before a divorce can be filed or granted. Montana's statute does not work that way. Two details in the wording show it:

  • The 180 days are counted "preceding the commencement of this proceeding." They look backward from the day the petition is filed. Nothing in the section starts a 180-day clock after filing.
  • The section offers serious marital discord as a complete alternative, with no time period attached.

Montana does have one short statutory wait. When one spouse files and serves the other, a decree may not be entered until 21 days after the date of service (MCA § 40-4-105(3)). That applies whether or not you have separated. See how long you have to wait.

What Serious Marital Discord Means

The statute does not define the phrase or give examples. What it does say is useful:

  • The discord must be serious.
  • It must adversely affect the attitude toward the marriage of "one or both" spouses. It does not have to be mutual.
  • A finding of irretrievable breakdown is "a determination that there is no reasonable prospect of reconciliation" (MCA § 40-4-107(3)).

The statute does not require proof of who caused the discord. Montana abolished fault defenses (MCA § 40-4-105(4)), and the chapter makes irretrievable breakdown the sole basis for dissolution (MCA § 40-4-101(5)). Our page on grounds for divorce in Montana explains why blame is not part of the test.

Living Under One Roof

Some couples keep sharing a home while they sort out a divorce, for financial reasons or for their children. Nothing in MCA § 40-4-104 makes separate households a condition of filing. A couple in that position can proceed on serious marital discord.

Whether spouses who share an address can also be found to have "lived separate and apart" is a different question. The statute does not define the phrase, and its text does not say whether separate bedrooms or separate lives within one house qualify. If the separation basis matters in your case, ask a lawyer how courts have read it. For a couple under one roof, the question may not need an answer, because the discord basis is available.

Sharing a home during a divorce is not right for everyone. If there is abuse or you are afraid of your spouse, your safety comes first. Call 911 in an emergency. The National Domestic Violence Hotline is 1-800-799-7233, and our Montana Domestic Violence Guide explains orders of protection.

If Your Spouse Says the Marriage Is Not Broken

MCA § 40-4-107 sets out what the court does in each situation:

  • Both spouses say under oath that the marriage is broken, or one says so and the other does not deny it. The court, after hearing, makes a finding whether the marriage is irretrievably broken (§ 40-4-107(1)).
  • One spouse denies it under oath. The court considers all relevant factors, including the circumstances that gave rise to the filing and the prospect of reconciliation. It then either makes the finding, or continues the matter for a further hearing "not fewer than 30 or more than 60 days later," or as soon after that as the court's calendar allows, and may suggest that the spouses seek counseling. At the later hearing the court makes the finding (§ 40-4-107(2)).

So a denial can add a pause, but the statute directs the court to decide the question at the adjourned hearing. A separation of more than 180 days is straightforward evidence in that situation, which is one reason it remains in the statute. See can my spouse refuse a divorce.

Separating Informally Before You File

Spouses are free to live apart without any court filing. Keep in mind what an informal separation does not do:

  • It does not divide property or debt. The court apportions property belonging to either or both spouses "however and whenever acquired" (MCA § 40-4-202(1)).
  • It does not create an enforceable parenting schedule or support order. Those come from a court.
  • It does not trigger the automatic economic restraining order, which is issued when a petition is filed (MCA § 40-4-126).

If you want enforceable terms while staying married, that is what a legal separation is for. If you are deciding when to start a case, see when is the right time to file and how divorce works in Montana.

This page explains Montana law in general as of the 2025 Montana Code Annotated. It is not legal advice about your specific situation.