A Montana common law marriage is a legally valid marriage formed without a license or ceremony when three things are true at the same time: both people are legally eligible to marry, they mutually consent to be married, and they live together while openly presenting themselves to the community as spouses. Once those elements are satisfied, the marriage carries every right and obligation of a licensed one, from joint tax filing to inheritance to spousal maintenance if the relationship ends. Montana statute expressly preserves this pathway: MCA 40-1-403 states that common law marriages “are not invalidated” by the marriage code.1Montana State Legislature. Montana Code 40-1-403 – Validity of Common-Law Marriage
The harder problem is proof. Because no license issues and no officiant signs anything, common law spouses often have no clear record of their marriage until they urgently need one, usually at a hospital, a probate court, or a divorce filing. Understanding what the law requires and building documentation early is the difference between a marriage that stands up in court and one that gets picked apart.
The Three Elements the Court Applies
The Montana Supreme Court uses a three-part test, and all three elements must be present.2Montana Judicial Branch. Marriage – Common Law Marriage
Competency. Both people must be legally eligible to marry: old enough, single, not closely related, and mentally capable of consenting.
Mutual consent. Both people must actually agree, in the present, to be married to each other. A shared plan to marry someday is not consent to be married now.
Cohabitation and public repute. The couple must live together and hold themselves out to the community as married.
What “Holding Out” Looks Like
The third element is where nearly every dispute lives. Living together is necessary but not sufficient, and there is no minimum length of cohabitation the law requires. The real question is whether the people around the couple, including family, friends, coworkers, and neighbors, understood them to be married.2Montana Judicial Branch. Marriage – Common Law Marriage
Evidence that supports public repute includes using the same last name, referring to each other as husband, wife, or spouse in conversation, listing each other as a spouse on insurance policies or loan applications, and filing joint tax returns.3Montana Department of Public Health and Human Services. ACA/Family Medicaid 308-2 Common Law Marriage No single fact wins or loses the question. Keeping separate last names does not disprove the marriage, and sharing a bank account does not prove it. Courts look at the pattern.
One thing is consistently fatal: secrecy. A common law marriage will not be found where the relationship was hidden from the community. The couple has to be publicly married, not privately in love.2Montana Judicial Branch. Marriage – Common Law Marriage
Who Can Form a Common Law Marriage
The eligibility rules match those for a licensed marriage. Both people must be at least 18, or at least 16 with judicial approval.4Montana State Legislature. Montana Code 40-1-202 – License Issuance Neither person can already be married, and the couple cannot be closely related, including parent and child, siblings, or first cousins.5Montana State Legislature. Montana Code 40-1-401 – Prohibited Marriages – Contracts
A marriage can be declared invalid if either person lacked mental capacity at the time, was under the influence of drugs or alcohol, or was coerced through force, duress, or fraud.6Montana State Legislature. Montana Code 40-1-402 – Declaration of Invalidity
Montana’s statutory text still contains a prohibition on same-sex marriage, but the U.S. Supreme Court’s 2015 decision in Obergefell v. Hodges struck down all such state bans. Same-sex couples can form a valid common law marriage in Montana under the same three-element test.
Getting the Marriage on Paper
The single most useful step a common law couple can take is filing a Declaration of Marriage without Solemnization under MCA 40-1-311. Both parties appear at a District Court Clerk’s Office with two witnesses and valid identification, sign the declaration in front of the clerk, and pay a filing fee; in Gallatin County the fee is $53.7Gallatin County, MT. Common Law Marriage / Declaration of Marriage The declaration creates an official court record of the marriage without a ceremony, and it heads off almost every proof problem that comes up later.
Even with a declaration on file, a common law couple should build overlapping documentation. Joint bank accounts, a shared mortgage or lease, beneficiary designations naming each other as spouse on insurance and retirement accounts, joint tax returns, and powers of attorney all reinforce the record. No one document decides the question, but a consistent pattern of treating each other as spouses across financial and legal documents is very hard for anyone to dispute.
Rights and Obligations During the Marriage
Federal Taxes
The IRS recognizes common law marriages that are valid in the state where they were formed. If your Montana common law marriage meets the three-element test, you are married for federal tax purposes and must file as married filing jointly or married filing separately. That remains true even if you later move to a state that does not permit new common law marriages.8Internal Revenue Service. Revenue Ruling 2013-17
Social Security and FMLA
The Social Security Administration recognizes valid common law marriages for survivor, retirement spousal, and disability benefits. Claiming those benefits requires specific evidence. If both spouses are living, the SSA typically asks for signed statements from both spouses plus statements from two blood relatives explaining why they believe the marriage exists. If one spouse has died, the surviving spouse provides a statement along with statements from two blood relatives of the deceased.9Social Security Administration. Code of Federal Regulations 404.726 – Evidence of Common-Law Marriage
The Family and Medical Leave Act defines “spouse” to include a husband or wife recognized in the state where the marriage was formed, which covers Montana common law marriages.10U.S. Department of Labor. Fact Sheet 28L – Leave Under the Family and Medical Leave Act A common law spouse can take FMLA leave to care for their partner on the same terms as anyone else.
Health Insurance and Medical Decisions
Adding a common law spouse to an employer-sponsored health plan is possible but rarely automatic. Employers and insurers typically require a signed, notarized affidavit of common law marriage along with supporting documentation such as a joint mortgage or lease, joint bank accounts, beneficiary designations, or powers of attorney. Requirements vary, so ask the benefits administrator what they need. A filed Declaration of Marriage from a Montana district court simplifies the process considerably.
Common law spouses also have the right to make medical decisions for an incapacitated partner, the same as any legal spouse. Hospitals may not accept that on your word alone, especially in an emergency, so a healthcare power of attorney naming your spouse is worth putting in place even though the underlying legal right already exists.
Inheritance Rights
A surviving common law spouse has the same inheritance rights as any surviving spouse. If the deceased left no will, Montana’s intestacy statute sets the surviving spouse’s share, and the amount depends on whether the deceased had children or surviving parents:11Montana State Legislature. Montana Code 72-2-112 – Share of Spouse
- No surviving children or parents: the surviving spouse inherits the entire estate.
- All children are also the surviving spouse’s children, and the surviving spouse has no other children: the surviving spouse inherits the entire estate.
- No surviving children, but a parent survives: the first $300,000 plus three-fourths of the remaining balance.
- Children are also the surviving spouse’s children, but the surviving spouse has other children from a different relationship: the first $225,000 plus one-half of the remaining balance.
- One or more children are not the surviving spouse’s children: the first $150,000 plus one-half of the remaining balance.
If a will tries to disinherit the surviving spouse, Montana’s elective share statute provides a floor. The surviving spouse can elect to take 50% of the marital-property portion of the augmented estate regardless of what the will says. If that comes out to less than $75,000, a supplemental amount brings the total up to $75,000.12Montana State Legislature. Montana Code 72-2-232 – Elective Share
The catch is the same as everywhere else in common law marriage: to claim any of these rights, the surviving spouse must prove the marriage existed. Without a Declaration of Marriage or strong documentation, the deceased’s other family members can challenge the marriage and potentially cut the surviving spouse out. Estate planning is not optional for common law couples. A will, up-to-date beneficiary designations, and ideally a filed declaration are essential.
Property, Debt, and Maintenance If the Marriage Ends
Montana is an equitable distribution state. A court divides marital property fairly based on the circumstances, not automatically 50/50. The statute directs the court to consider the length of the marriage, each spouse’s age, health, income, employability, debts, and needs, and custodial arrangements for children, along with each spouse’s contribution “as a homemaker or to the family unit.”13Montana State Legislature. Montana Code 40-4-202 – Division of Property A spouse who stayed home while the other built a career is not penalized for lacking income during the marriage.
Property acquired before the marriage, gifts, and inheritances received by one spouse are treated differently. Courts can still divide them, but must specifically weigh the other spouse’s contributions to maintaining or growing that property and whether the division serves as an alternative to maintenance. Premarital property tends to stay with its original owner unless it was significantly commingled or the other spouse contributed meaningfully to its upkeep.
Debts incurred by one spouse are generally that spouse’s responsibility unless the debt benefited the marriage (food, housing, childcare, necessary household expenses) or both spouses jointly signed. A creditor pursuing one spouse’s separate debt cannot reach the other spouse’s separate income or property. Joint debts and family-necessity debts can be collected from either spouse’s income or from jointly held property.
Spousal maintenance is available on the same terms as in any Montana divorce. A court can award it only if the spouse requesting it lacks enough property to cover reasonable needs and is either unable to support themselves through employment or is caring for a child whose situation makes outside employment inappropriate. Both conditions must be met before the court sets an amount and duration. Marital misconduct plays no role. The statute expressly bars the court from considering it in either property division or maintenance.14Montana State Legislature. Montana Code 40-4-203 – Maintenance
How to End a Common Law Marriage
A common law marriage ends the same way a licensed one does: through a formal dissolution in Montana district court. Moving out is not enough. If the marriage is valid, you need a divorce.
The filing spouse must have been domiciled in Montana, or stationed in Montana as a military member, for at least 90 days before filing. The court must find the marriage is “irretrievably broken,” supported by evidence that the parties have lived apart for at least 180 days or that serious marital discord exists.15Montana State Legislature. Montana Code 40-4-104 – Dissolution of Marriage – Legal Separation Montana is a no-fault state; nothing turns on proving the other spouse did anything wrong.16Montana Judicial Branch. Divorce, Dissolution, Legal Separation, Annulment The filing fee to start a dissolution is $200.17Montana Judicial Branch. Fee Schedule – Civil Montana Clerks of District Courts
The wrinkle unique to common law divorce is that the petitioner may first have to prove the marriage existed. If the other party denies it, the court applies the same three-element test. Joint tax returns, shared financial accounts, insurance beneficiary designations, and statements from family or friends who understood the couple to be married all serve as evidence. The more consistently the relationship was treated as a marriage in public, the stronger the case.
What Happens If You Leave Montana
Under the Full Faith and Credit Clause, most states will honor a common law marriage validly formed in Montana even if they no longer allow new common law marriages within their own borders.18Constitution Annotated. Overview of Full Faith and Credit Clause The operative word is “validly formed.” If the new state questions the marriage, the couple may need to prove the three elements were satisfied while they lived in Montana. A filed Declaration of Marriage is the cleanest proof. Copies of joint tax returns, insurance policies listing each other as spouse, and other records showing a consistent pattern of married life are the backup. Federal recognition follows the IRS rule: if the marriage was valid where formed, it is valid for federal tax and benefits purposes wherever you live.8Internal Revenue Service. Revenue Ruling 2013-17