Does Missouri recognize common law marriage?
Yes, common law marriage is legal in Missouri. In fact, all Missouri courts must recognize common law marriages that predated 1/1/1987. In a case from 1998, In re Estate of Lawson established that where the parties were validly married under the prior common law rules, that marriage remained valid after the law changed and the couple’s marriage was not invalidated because a statute had changed. The new statute was not retroactive and did not affect any existing common law marriages , only those established after the change in the law.
With regard to new common law marriages, there are no decisions yet, nor any legal authority. So, while courts in Missouri must recognize the common law marriages that occurred before 1/1/1987, they have nothing to say about those after. And obviously, the statute overturning common law marriages in Missouri specifically states that it does not apply retroactively, so any new common law marriages would not be recognized.

Requirements of common law marriage and its history
At common law, the requirements for a valid marriage included: (1) the legal capacity of the parties (i.e., age, mental competency, marital status, etc.); (2) the voluntary consent of the parties; and (3) the marriage contract or act. The lack of any one of these elements rendered a purported marriage invalid at common law. Although the marriage act was recognized as the essential element of a valid marriage, the precise nature of the marriage contract was never strictly defined. Generally, the contract was viewed simply as an expression of agreement to marry. No particular ceremony was required, although there were customary practices that parties sometimes followed.
In the past, Missouri recognized common law marriages. However, in 1989, the Missouri General Assembly abolished common law marriages and declared that all marriages contracted after 1989, regardless of parties’ intent to marry, shall be void. Currently, for a marriage to be valid under Missouri law, "a marriage contract is required to be entered into by two persons of the legal age and capacity as prescribed by law . . ." A marriage is contracted by the parties if they "(1) enter into a ceremonial marriage pursuant to [Chapter 451] . . . or (2) establish a marriage otherwise valid by the laws of this state."
The Missouri Supreme Court has applied the substantive common law requirement that a contract is essential to the validity of all marriages, whether formalized by license or not, well before 1989. Prior to the abolition of common law marriages, Missouri courts had held that the parties must have made an agreement to marry and the marriage act (ceremony) must have been performed. Further, the Missouri Supreme Court had adopted the following theory in determining whether a common law marriage existed:
A combination of conduct evidencing an agreement to be married and manifesting of mutual consent between the parties to the relationship in words or acts, conspicuously evidencing a mutual agreement, constitutes the marriage contract. . . Whether linguistic or non-linguistic, the conduct involved must be such as can be adequately explained only as an expression of the parties’ desire to enter into the legal relationship secured by a ceremonial marriage.
Additionally, Missouri courts had held that this fundamental understanding applied regardless of whether the parties had engaged in sexual activity. In short, prior to 1989, a marriage did not require the performance of a marriage ceremony; however, the requirement of a contract between the parties remained jurisdictionally mandatory.
Options other than common law marriage in Missouri
While common law marriage may not be an option for couples in Missouri, there are still many alternatives that provide numerous options for unmarried couples to make their long-term relationship more secure and formal. These alternatives include cohabitation agreements, domestic partnerships, and separate or joint wills. A couple that is considering a cohabitation agreement may want to consider whether they believe their relationship is serious enough to warrant one. A cohabitation agreement can be used to protect each party’s right to property, establish how assets will be divided in the event of separation or divorce, the rights each party has in the event of the death of the other party, what will happen to jointly held property if one party dies, and in what location any jointly held property will be located.
Every state has its own policies regarding domestic partnerships. It may be a good idea for a couple to check with the courthouse in their county in order to find out what is required for domestic partnerships in Missouri. In Jackson County, for example, a couple can file a declaration of domestic partnership as long as they meet certain requirements. A domestic partnership does not provide the same tax and spousal social security benefits as those given to married couples. However, it does allow each partner to leave property to the other without estate tax consequences.
Separate or joint wills are another way that unmarried couples can take steps to protect each other from losing their assets upon the death of one party. Each partner can draft a will stating what will happen to their property should they die. A state can dictate who inherits property if a person dies without a will or intestate. If the partners are unable to draft a joint will due to state laws, separate wills work as an alternative. Inheritance and domestic relations laws are extremely complex, so people seeking assistance with wills and domestic partnerships should consult a reliable legal professional.
Legacy of common law marriages
Navigating common law marriage legacies is essential for couples who have relocated to Missouri from states where common law marriage is recognized. In these situations, the Missouri court system can entertain the validity of such an arrangement by conducting an examination of the couple’s status involving a common law marriage.
To protect spouses and children who could potentially be left without due inheritance as a result of the disposition of the deceased person’s estate, Missouri courts need to establish whether or not the decedent was in a common law marriage with his or her partner. A court of law in Missouri may recognize a common law marriage that was created in a state that recognizes such unions, which is a "legacy" of the first state to the new state where the couple resides . To bring a legacy of common law marriage into Missouri’s court system, it will be necessary to file a petition pursuant to RSMo 476.120 related to the decedent’s estate.
To support the claim that a common law marriage exists, the couple must present legitimate evidence such as important dating documents, testimony, affidavits, or other formal evidence deemed acceptable by the court system. A sworn statement under RSMo 476.120 establishes that the decedent left such instructions to the probate court in the new state. Other forms of documentation may also be acceptable through judicial determination or litigation.
Legal effect of common law marriage
Although Missouri does not recognize common law marriages, many people mistakenly believe that they do have a common law marriage and that there are certain legal rights and privileges that go along with this "marriage". While many states allow different kinds of "nontraditional marriages", including common law marriages, a couple intending to marry in Missouri may still be held to the restrictions that Missouri places on legal marriage. In Missouri, a marriage license is required, and couples legally married in other states are eligible for spousal rights upon establishing residency in Missouri.
Without a legal marriage, a couple will not enjoy the rights or privileges granted to married people. This includes the division of property in the event of a divorce or death. In a standard divorce proceeding, courts will divide all property owned by the couple. As long as there is joint ownership and proof of equitable participation (joint and contributing effort) in the acquisition of the particular property and both parties are entitled to a benefit from the property, it will be included in the division . If a couple is not legally married and own property together or have acquired property during their time together, Missouri courts will not divide that property without a clear understanding of how property was acquired, maintained and ferreted out with respect to ownership interests. This can get very complicated and therefore, expensive as well as emotionally draining.
In the unfortunate event of death, property specified in a will and fall under intestacy laws will be included as part of the estate subject to probate. A partner in a common law marriage will have no rights to jointly held assets and no other rights to any property owned by the deceased partner unless clear writing to that effect is included in the estate plan. Otherwise, the partner in a common law marriage has no inheritance rights in Missouri.
Legal decisions regarding health care and medical needs should be discussed with married couples; however, decisions regarding health care also requires legal, written documentation. An individual cannot make decisions regarding a spouse’s health care without the spouse’s consent unless a durable power of attorney has been established. In Missouri, a common law marriage is not a recognized entity and like many decisions regarding health care and medical needs, the spouse must have a duly executed durable power of attorney.