No amount of time living together creates a common law marriage in Missouri. State law declares all common law marriages formed in Missouri “null and void,” so whether you’ve shared a home for seven years, seventeen, or thirty, you are not legally married and you have none of the rights a spouse would have.1Missouri Revisor of Statutes. Missouri Code 451.040 – Marriage License Required, Waiting Period The one exception is a common law marriage that was validly formed in another state before you moved here; Missouri generally honors those.
The Statute Leaves No Room
Missouri’s marriage law is direct: “Common-law marriages shall be null and void.”1Missouri Revisor of Statutes. Missouri Code 451.040 – Marriage License Required, Waiting Period Every marriage in the state must begin with a license from a county Recorder of Deeds and be performed by someone authorized under Missouri law. Skip either step and, in the state’s eyes, no marriage exists.
The “seven-year rule” people sometimes mention is a myth everywhere in the country, but it causes particular trouble in Missouri because the state offers no informal path to marriage at all. A couple could share a mortgage, raise children together, use the same last name, and introduce each other as spouses for decades. Legally, they remain two single people.
What You Lose Without a License
Marriage carries a bundle of automatic legal protections that unmarried partners simply don’t have. The gaps tend to surface at the worst moments: a hospital stay, a death, or a breakup.
- Inheritance: A surviving spouse inherits a share of the estate under Missouri law even without a will. An unmarried partner inherits nothing by default.
- Medical decisions: Spouses are generally recognized as next of kin. An unmarried partner can be shut out of medical decision-making entirely if the other partner becomes incapacitated without a healthcare power of attorney.
- Property division: Divorcing spouses go through equitable division. When unmarried couples split, each person walks away with whatever is titled in their name, regardless of who paid.
- Taxes: Married couples can file jointly and claim spousal deductions. Unmarried partners file as single individuals.
- Employer benefits: Many health insurance and retirement plans extend to spouses automatically but not to unmarried partners.
Common Law Marriages Formed in Another State
Missouri will not let you form a common law marriage here, but it will generally recognize one that was validly created in a state that allows them. About ten states and the District of Columbia still permit some form of common law marriage, including Colorado, Iowa, Kansas, Montana, South Carolina, Texas, and Utah.2National Conference of State Legislatures. Common Law Marriage by State Each sets its own standards, but most require that both partners agreed to be married, lived together, and presented themselves to the community as spouses.
Missouri’s recognition rests on the Full Faith and Credit Clause of the U.S. Constitution, which requires every state to honor the valid legal acts of other states.3Constitution Annotated. Overview of Full Faith and Credit Clause If you and your partner established a common law marriage in Kansas and later moved to Missouri, a Missouri court would treat you as married, provided your marriage satisfied Kansas’s requirements at the time it was formed.
“Validly” is the operative word. Missouri courts apply the originating state’s rules, not Missouri’s. Simply having lived together in a common-law-friendly state and claiming marriage after the fact is where most of these disputes fall apart.
Proving the Marriage
There is no marriage certificate to produce, which makes proof difficult. If you need to establish marital status in Missouri for a legal proceeding, expect to provide sworn statements from both partners and, ideally, from relatives or close friends who can confirm the relationship. Joint tax returns, shared accounts, insurance policies naming each other as spouses, and documents using a shared last name all help.
Federal Rules Can Differ
Federal agencies follow their own recognition rules, and those are more generous than you might expect for someone who moved from a common-law state.
IRS Filing Status
The IRS considers you married if your common law marriage is recognized either by the state where you currently live or by the state where the marriage began.4Internal Revenue Service. Publication 501 – Dependents, Standard Deduction, and Filing Information If you established a valid common law marriage in Texas and now live in Missouri, you are married for federal tax purposes and must file as married filing jointly or married filing separately. Filing as single would be incorrect.5Internal Revenue Service. Revenue Ruling 2013-17
Social Security
The Social Security Administration also recognizes valid common law marriages for survivor benefits, spousal benefits, and other entitlements. The SSA prefers signed statements from both spouses and two blood relatives explaining why they believe the marriage existed; if a spouse has died, statements from the survivor and two of the deceased’s blood relatives can serve the same purpose.6Social Security Administration. 20 CFR 404.726 – Evidence of Common-Law Marriage
Protecting Yourselves Without Marrying
Because Missouri will not treat you as married no matter how long you live together, the only way to build legal protection is to create it yourselves through written agreements and planning. None of it is automatic.
Cohabitation Agreement
A cohabitation agreement is a written contract between unmarried partners covering who owns what, how expenses are shared, and what happens to property if the relationship ends. Missouri courts enforce contracts between adults, so a properly drafted agreement gives you a framework that cohabitation alone never will.
How You Title Property
Titling matters enormously when you aren’t married. If you buy a house together but only one partner is on the deed, the other has no ownership interest, regardless of who contributed what. For a surviving partner to inherit a jointly owned home automatically, the deed must specifically create a joint tenancy with right of survivorship. That language has to appear explicitly, because Missouri does not presume survivorship for co-owners who aren’t married to each other.
Healthcare Power of Attorney and a Will
Your partner has no automatic right to make medical decisions for you. A healthcare power of attorney naming your partner as your agent fixes that. A will naming your partner as a beneficiary is the only way to ensure they inherit from your estate; without one, Missouri’s intestacy laws direct your property to blood relatives, and an unmarried partner receives nothing.
Paternity for Children
Married couples get an automatic presumption that the husband is the legal father of a child born during the marriage. Unmarried couples don’t. To establish legal paternity, the parents can sign an Affidavit Acknowledging Paternity at the hospital when the baby is born, which adds the father’s name to the birth certificate. If that step is missed, parents can complete the affidavit later through the Bureau of Vital Records or the Family Support Division, or get a court order.7Missouri Department of Social Services. Establish Paternity
This step is not optional if the father wants legal rights. Until paternity is legally established, the father has no standing to seek custody or visitation, and no child support order can be entered. Free genetic testing is available through the Family Support Division, but testing alone does not create legal paternity; the affidavit or court order is still required, and results must show at least a 98 percent probability to create a legal presumption of fatherhood.7Missouri Department of Social Services. Establish Paternity
If You Want the Spousal Rights, You Need a License
Marriage in Missouri starts with a license from a county Recorder of Deeds.1Missouri Revisor of Statutes. Missouri Code 451.040 – Marriage License Required, Waiting Period Both partners must appear in person and sign the application in front of the recorder or a deputy, bringing proof of a Social Security number and a government-issued ID showing date of birth. There is no waiting period, and the license is good for 30 days.8Henry County, Missouri. Recorder of Deeds Office Both partners must be at least 18; Missouri law allows no exceptions and courts cannot authorize underage marriages.9Missouri Revisor of Statutes. Missouri Code 451.090 – Issuance of License Prohibited, When – Proof of Age The ceremony must be performed by someone authorized under Missouri law, which includes clergy in good standing with a Missouri church or synagogue and judges acting without compensation.10FindLaw. Missouri Code 451.100 – Marriages Solemnized by Whom After the ceremony, the officiant returns the completed license to the Recorder of Deeds office that issued it, and following up to confirm filing saves trouble later when you need proof of marriage.