Missouri is not a common law marriage state. Section 451.040 of the Missouri Revised Statutes declares such arrangements “null and void,” and the state has held that position since the early 1920s.1Missouri Revisor of Statutes. Missouri Revised Statutes Title XXX Chapter 451 Section 451-040 No matter how long you have lived together, shared finances, or introduced each other as spouses, none of that creates a marriage in Missouri. There is one narrow exception: if you formed a valid common law marriage in a state that allows them before moving here, Missouri will recognize it.
What the Missouri Statute Actually Says
The wording of Section 451.040 leaves no wiggle room. Common law marriages are void, full stop.1Missouri Revisor of Statutes. Missouri Revised Statutes Title XXX Chapter 451 Section 451-040 There is no threshold of years, no set of behaviors, no combination of shared bank accounts and joint tax filings that will convert a Missouri cohabitation into a marriage. A couple who lived together in Missouri for forty years, raised children, and called each other husband and wife the entire time still has no marriage under Missouri law when one of them dies or the relationship ends.
Missouri offers exactly one route to a legal marriage: a license from the county Recorder of Deeds, followed within 30 days by a ceremony performed by an authorized officiant.2Missouri Revisor of Statutes. Revised Statutes of Missouri, RSMo Section 451.100 Skip either step and no marriage exists.
When Missouri Recognizes an Out-of-State Common Law Marriage
The ban applies only to marriages formed within Missouri’s borders. Under the Full Faith and Credit Clause of the U.S. Constitution, Missouri will honor a common law marriage that was validly created in a state that permits them.1Missouri Revisor of Statutes. Missouri Revised Statutes Title XXX Chapter 451 Section 451-040 Once that recognition attaches, the couple has every right a licensed married couple has: joint tax filing, medical decision-making, intestate inheritance, spousal maintenance in a divorce. Ending the relationship requires a formal dissolution of marriage in the courts.
Timing controls everything. The marriage must have been fully established under the other state’s requirements before the couple set foot in Missouri as residents. You cannot start a common law marriage in Kansas, move to Missouri before meeting every Kansas requirement, and finish the process here. Missouri does not let another state’s law finish forming on Missouri soil. The marriage either existed when you crossed the state line, or it never did.
Which States Could Have Created One
Only a small group of states still allows new common law marriages: Colorado, Iowa, Kansas, Montana, Oklahoma, Rhode Island, South Carolina, Texas, and Utah, along with the District of Columbia.3Social Security Administration. POMS GN 00305.075 – State Laws on Validity of Common-Law Non-Ceremonial Marriages New Hampshire recognizes them in one narrow situation only: after at least three years of cohabitation, when one partner dies, the survivor is treated as a spouse for inheritance.
Each of these states sets its own requirements. Most demand that both partners intend to be married, live together, and hold themselves out publicly as a married couple. Simply sharing an address for years is not enough anywhere.
Several states have shut the door with a cutoff date, and the date matters. Alabama, for example, stopped recognizing new common law marriages after January 1, 2017, though marriages formed before that date remain valid.4Alabama Legislature. Alabama Code Title 30 Chapter 1 Section 30-1-20 Pennsylvania, Georgia, and others have similar cutoffs from earlier years. A couple whose relationship began in one of these states after the cutoff has no common law marriage to bring into Missouri, regardless of how the relationship looked.
Proving Your Out-of-State Marriage in Missouri
If you rely on an out-of-state common law marriage in Missouri, the burden of proof falls on you. The question comes up in divorce, probate disputes, insurance claims, and applications for federal benefits. You will need to show that every requirement of the state where the marriage formed was satisfied.
Evidence that carries weight includes:
- Sworn statements from both partners describing when and where you agreed to be married, along with affidavits from friends and family who understood you to be married.
- Joint bank accounts, shared mortgages or leases, loans in both names, and jointly filed tax returns.
- A driver’s license or Social Security card reflecting a shared surname, or birth certificates listing both partners as parents.
- Insurance policies naming the partner as spouse or beneficiary, and employer records treating the partner as immediate family.
The Social Security Administration applies its own proof standard for common law marriage claims. It wants signed statements from both partners, or from the survivor if one has died, plus statements from blood relatives of each spouse. When relatives are unavailable, statements from others with knowledge of the relationship along with supporting documents can substitute.5Social Security Administration. Code of Federal Regulations Section 404-0726 Assembling this evidence while both partners are living is far easier than trying to reconstruct it later.
What Unmarried Couples in Missouri Lose
Because Missouri offers no common law option, couples who never took out a license have none of the default legal protections that come with marriage. The gaps are largest in three areas: property, inheritance, and decision-making during illness.
Property and Debts
Missouri’s divorce statute directs courts to divide marital property and debts in proportions the court deems just when a marriage ends.6Missouri Revisor of Statutes. Revised Statutes of Missouri, RSMo Section 452.330 None of that touches unmarried couples. Ownership follows title. Whoever’s name is on the deed, the vehicle, or the account owns it, even if the other partner contributed for years. There is no automatic right to spousal support and no presumption that anything acquired during the relationship is shared.
The independence runs both ways. You are generally not liable for a partner’s individual debts. But cosign a loan, share a credit card, or open a joint account, and you are on the hook for the whole balance.
A written cohabitation agreement is the most effective tool for closing these gaps. It functions like a prenuptial agreement for unmarried partners, spelling out who owns what, how expenses are handled, and what happens if the relationship ends. Titling real estate as joint tenants with right of survivorship also protects the survivor if one partner dies, but the deed has to say “joint tenancy with right of survivorship” specifically. Otherwise Missouri may treat the owners as tenants in common, and the deceased partner’s share passes to their family rather than to the surviving partner.
Inheritance
This is the widest gap, and the one that catches unmarried couples most often. Missouri’s intestate succession statute passes an estate first to a surviving spouse, then to children, then to parents and siblings, and outward through the family tree.7Missouri Revisor of Statutes. Revised Statutes of Missouri, RSMo Section 474.010 An unmarried partner appears nowhere in that order. If your partner dies without a will, you inherit nothing under Missouri law. The home you shared, the savings you built together, all of it goes to your partner’s blood relatives.
A will directs probate assets, but many of the largest assets a person owns skip probate entirely. Life insurance, retirement accounts, and payable-on-death bank accounts go to whoever is named as beneficiary on the account itself. Married spouses enjoy some default beneficiary protections under federal law for certain retirement accounts; unmarried partners get none of that. Every one of these accounts has to be reviewed and updated by name, or the money goes wherever the last-filed form said.
Medical and Financial Decisions
When a spouse becomes incapacitated, the other spouse has legal standing to make medical and financial decisions. An unmarried partner has none. Hospitals and banks will turn to parents, adult children, or siblings instead.
Two documents fix this. A durable power of attorney for healthcare lets you name your partner as the person who makes medical decisions when you cannot. A durable financial power of attorney authorizes your partner to manage accounts and pay bills during your incapacity. “Durable” means the authority survives your incapacity, which is the moment you need it.
Missouri’s Compassionate Care Visitation Act does let patients designate visitors in healthcare facilities, including unmarried partners.8Missouri Revisor of Statutes. Revised Statutes of Missouri, RSMo Section 191.1400 Visitation is not decision-making, though. Being allowed in the room does not let you direct care. Both documents need to be signed while both partners are healthy and competent, because once one partner loses capacity, it is too late to create them.
Federal Benefits Follow State Law
Federal agencies look to state law to decide whether a marriage exists. Social Security will pay survivor and spousal benefits based on a common law marriage, but only if the marriage was valid under the law of the state where the couple lived.5Social Security Administration. Code of Federal Regulations Section 404-0726 For a Missouri couple with no recognized out-of-state common law marriage in their history, that means no survivor benefits and no ability to claim on a deceased partner’s Social Security record. The couple’s private planning documents are what stand between the surviving partner and losing everything the two of them built.