Common-law marriage in the United States
Common-law marriage in the United States can still be contracted in nine states (Alabama, Colorado, Kansas, Rhode Island, South Carolina, Iowa, Montana, Utah and Texas) and the District of Columbia. New Hampshire recognizes common-law marriage for purposes of probate only, and Utah recognizes common-law marriages only if they have been validated by a court or administrative order.Common-law marriage can no longer be contracted in 27 states, and was never permitted in 13 states. The requirements for a common-law marriage to be validly contracted differ from state to state. Nevertheless, all states — including those that have abolished the contract of common-law marriage within their boundaries — recognize common-law marriages lawfully contracted in those jurisdictions that permit it. Some states that do not recognize common law marriage also afford legal rights to parties to a putative marriage (i.e. in circumstances when someone who was not actually married, e.g. due to a failure to obtain or complete a valid marriage license from the proper jurisdiction, believed in good faith that he or she was married) that arise before a marriage's invalidity is discovered.
The principle of common-law marriage was affirmed by the United States Supreme Court in Meister v. Moore (96 U.S. 76 (1877)), which ruled that Michigan had not abolished common law marriage merely by producing a statute establishing rules for the solemnization of marriages.
The status of common-law marriage in the United States varies by state. In Meister v. Moore, 96 U.S. 76 (1877), the United States Supreme Court, relying on Hutchins v. Kimmell, 31 Mich. 126 (1875) ruled that Michigan had not abolished common-law marriage merely by producing a statute which established rules for the solemnization of marriages, because it did not require marriages to be solemnized: it required only that, if a marriage was solemnized, it could be solemnized only as provided by law. Otherwise, the court found that, as the right to marry existed at common law, the right to marriage according to the tradition of that common law remained valid until such time as state law affirmatively changed it. The Court did not find it necessary to pass special legislation specifically outlawing the common law contract of a marriage, but it was sufficient for a state's general marriage statutes to clearly indicate no marriage would be valid unless the statutory requirements enumerated were followed.
While a number of U.S. states recognize either same-sex marriage, or domestic partnerships with the same legal incidents, as marriage, no U.S. state except Iowa and Rhode Island, where the law is untested, currently recognizes same sex common-law marriages. The Federal Defense of Marriage Act permits any state to not recognize same-sex marriages from another state, but the federal government will recognize them.
A common-law marriage is recognized for federal tax purposes if it is recognized by the state where the taxpayers currently live, or in the state where the common-law marriage began. If the marriage is recognized under the law and customs of the state in which the marriage takes place (even if the state is a foreign country), the marriage is valid (Rev. Rul. 58-66). Practitioners should be alert to the specific state requirements necessary for their clients contemplating filing joint returns under common-law marriage statutes.
Availability by state
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Common-law marriage can still be contracted in nine states (Alabama, Colorado, Kansas, Rhode Island, South Carolina, Iowa, Montana, Utah and Texas) and the District of Columbia. New Hampshire recognizes common-law marriage for purposes of probate only, and Utah recognizes common-law marriages only if they have been validated by a court or administrative order.
Note there is no such thing as "common-law divorce" — that is, you cannot get out of a common-law marriage as easily as you can get into one. Only the contract of the marriage is irregular; everything else about the marriage is perfectly regular. People who marry per the old common law tradition must petition the appropriate court in their state for a dissolution of marriage.
The situation in Pennsylvania became unclear in 2003 when an intermediate appellate court purported to abolish common-law marriage even though the state Supreme Court had recognized (albeit somewhat reluctantly) the validity of common-law marriages only five years before. The Pennsylvania legislature resolved most of the uncertainty by abolishing common-law marriages entered into after January 1, 2005. However, it is still not certain whether Pennsylvania courts will recognize common-law marriages entered into after the date of the Stamos decision and before the effective date of the statute (i.e., after September 17, 2003, and on or before January 1, 2005), because the other intermediate appellate court has suggested that it might not follow the Stamos decision.
Common-law marriages can no longer be contracted in the following states, as of the dates given: Alaska (1917), Arizona (1913), California (1895), Florida (1968), Georgia (1997), Hawaii (1920), Idaho (1996), Illinois (1905), Indiana (1958), Kentucky (1852), Maine (1652, when it became part of Massachusetts; then a state, 1820), Massachusetts (1646), Michigan (1957), Minnesota (1941), Mississippi (1956), Missouri (1921), Nebraska (1923), Nevada (1943), New Mexico (1860), New Jersey (1939), New York (1933, also 1902–1908), North Dakota (1890), Ohio (1991), Oklahoma (Nov. 2010), Pennsylvania (2005), South Dakota (1959), and Wisconsin (1917).
The following states never permitted common-law marriages: Arkansas, Connecticut, Delaware, Louisiana, Maryland, North Carolina, Oregon, Tennessee, Vermont, Virginia, Washington, West Virginia, and Wyoming. Note that common-law marriage was never known in Louisiana, which is a French civil or code law jurisdiction, not an English common law jurisdiction. As such, it is a former Council of Trent jurisdiction.
Nevertheless, all states — including those that have abolished the contract of common-law marriage within their boundaries — recognize common-law marriages lawfully contracted in those jurisdictions that permit it. This is because all states provide that validity of foreign marriage is determined per lex loci celebrationis - that is, "by law of the place of celebration." Thus, a marriage validly contracted in Ohio, including common-law marriages entered into before that state abolished new common-law marriages in 1991, is valid in Indiana, even if it could not be legally contracted in Indiana because Ohio law is the basis of its validity. However, a marriage that was not lawfully contracted in Ohio would not be valid in Indiana even if it could have been lawfully contracted there, by the same principle.
Common law marriage determinations frequently refrain from identifying a specific date of marriage in common law marriage cases when this is not necessary, because often, there is no one marriage ceremony that establishes this date. Even when a relationship begins in a state that does not recognize common law marriage, a common law marriage between the parties is often recognized if that relationship continues at a time when the parties relocate to a state that does recognize common law marriage. It is not uncommon for someone to claim to be a spouse based upon time the couple spent together in a common law marriage state even after the couple leaves that state. The case law does not definitively establish whether a brief presence in a common law marriage state by a couple who otherwise are eligible to have a common law marriage, that does not establish domicile in that state, gives rise to a common law marriage that must be recognized in a state that does not itself have common law marriage.
Additionally, some courts have held that all marriages performed within the U.S. must be valid in all states under the Full Faith and Credit Clause of the U.S. Constitution. However, none of the cases to date has actually used the Clause to validate a sister-state marriage, and the question shows no sign of reaching the U.S. Supreme Court - whose decision would apply nationally, not just locally or within a federal circuit.
The requirements for a common-law marriage to be validly contracted differ in the eleven states which still permit them.
A valid common law marriage exists when there is capacity to enter into a marriage, the man and woman must be at least 16 with legal parental consent and present agreement or consent to be husband and wife, public recognition of the existence of the marriage after 181 days, and consummation.
The elements of a common-law marriage are, with respect to both spouses: (1) holding themselves out as husband and wife; (2) consenting to the marriage; (3) cohabitation; and (4) having the reputation in the community as being married. Different sources disagree regarding the requirement of cohabitation and some indicate that consummation (i.e. post-marital sexual intercourse) is also an element of common law marriage. Colorado, by statute, no longer recognizes common law marriages entered by minors in Colorado, and also does not recognize foreign common law marriages entered into by minors, even if that marriage would have been valid where entered into under local law. See Section 14-2-109.5, Colorado Revised Statutes. The constitutionality of this limitation as applied to foreign marriages has not been tested in litigation.
District of Columbia
"A marriage that is legally recognized even though there has been no ceremony and there is no certification of marriage. A common-law marriage exists if the two persons are legally free to marry, if it is the intent of the two persons to establish a marriage, and if the two are known to the community as husband and wife."
Common-law marriages have been recognized in the District of Columbia since 1931.
The three elements of a common-law marriage are: (1) the present intent and agreement to be married; (2) continuous cohabitation; and (3) public declaration that the parties are husband and wife. Martin, 681 N.W.2d at 617. The public declaration or holding out to the public is considered to be the acid test of a common-law marriage.
701—73.25 Common law marriage. (cut and pasted from Iowa Law) A common law marriage is a social relationship between a man and a woman that meets all the necessary requisites of a marriage except that it was not solemnized, performed or witnessed by an official authorized by law to perform marriages. The necessary elements of a common law marriage are: (a) a present intent of both parties freely given to become married, (b) a public declaration by the parties or a holding out to the public that they are husband and wife, (c) continuous cohabitation together as husband and wife (this means consummation of the marriage), and (d) both parties must be capable of entering into the marriage relationship. No special time limit is necessary to establish a common law marriage. This rule is intended to implement Iowa Code section 425.17.
Under Kansas Statute 23-2502, both parties to a common-law marriage must be 18 years old. The three requirements that must coexist to establish a common-law marriage in Kansas are: (1) capacity to marry; (2) a present marriage agreement; and (3) a holding out of each other as husband and wife to the public.
A common-law marriage is established when a couple: "(1) is competent to enter into a marriage, (2) mutually consents and agrees to a common law marriage, and (3) cohabits and is reputed in the community to be husband and wife." 
New Hampshire recognizes common-law marriage for purposes of probate only. In New Hampshire "[P]ersons cohabiting and acknowledging each other as husband and wife, and generally reputed to be such, for the period of 3 years, and until the decease of one of them, shall thereafter be deemed to have been legally married." Thus, the state posthumously recognizes common-law marriages to ensure that a surviving spouse inherits without any difficulty.
The criteria for a common-law marriage are: (1) the parties seriously intended to enter into the husband-wife relationship; (2) the parties’ conduct is of such a character as to lead to a belief in the community that they were married.
The criteria for a common law marriage are: (1) when two parties have a present intent (usually, but not necessarily, evidenced by a public and unequivocal declaration) to enter into a marriage contract; and (2) "a mutual agreement between the parties to assume toward each other the relation of husband and wife."  Common law marriages can dissolve in legal divorce and alimony.
Common-law marriage is known as an "informal marriage", which can be established either by declaration (registering at the county courthouse without having a ceremony), or by meeting a 3-prong test showing evidence of (1) an agreement to be married; (2) cohabitation in Texas; and (3) representation to others that the parties are married. In the actual wording of the law there is no specification on the length of time that a couple must cohabitate to meet the second requirement of the 3-prong test. Under Texas law there is no required period of time of cohabitation and an informal marriage can occur if the couple lives together one day if the other elements, (an agreement to be married and holding out as married to the public) have also occurred. Likewise a couple can live together for 50 years and if they never have an agreement to be married, or hold themselves out to the public as married, their 50 year cohabitation will not make them informally married. If a couple does not commence a proceeding to prove their relationship was a marriage within two years of the end of their cohabitation and relationship there is a legal presumption that they were never informally married, but this presumption is rebuttable. In other words, even after two years a party to the relationship, or another interested party such as their estate, can seek to establish the marriage if they can overcome the presumption. Because this rule is only a presumption, and not a statute of limitations, a person in Texas that could be informally married should always go through a divorce proceeding when the relationship ceases or face possible serious legal repercussions.
Utah recognizes common-law marriages only if they have been validated by a court or administrative order. For a common-law marriage to be legal and valid, "a court or administrative order must establish that" the parties: (1) "are of legal age and capable of giving consent"; (2) "are legally capable of entering a solemnized marriage under the provisions of Title 30, Chap. 1 of the Utah Code; (3) "have cohabited"; (4) "mutually assume marital rights, duties, and obligations"; and (5) "hold themselves out as and have acquired a uniform and general reputation as husband and wife"  In Utah, the fact that two parties are legally incapable of entering into a common law marriage, because they are already married, does not preclude criminal liability for bigamy or polygamy.
Some states have abolished common law marriage, in that such marriages cannot be contracted anymore in those states, but they continue to recognize common law marriages which have been contracted in the past, before a specific date. Georgia recognizes common law marriages created before January 1, 1997; Idaho - created before January 1, 1996; Ohio - created before October 10, 1991; Oklahoma - created before November 1, 1998; Pennsylvania - created before January 1, 2005. 
- PNC Bank Corporation v. Workers' Compensation Appeal Board (Stamos), 831 A.2d 1269 (Pa. Cmwlth. 2003)
- Staudenmayer v. Staudenmayer, 552 Pa. 253, 714 A.2d 1016 (1998).
- Act 144 of 2004, amending 23 Pa.C.S. Section 1103.
- Compare Bell v. Ferraro, 2004 PA Super 144, 849 A.2d 1233 (4/28/2004), with Stackhouse v. Stackhouse, 2004 PA Super 427, 862 A.2d 102 (11/10/2004).
- See e.g. Thomas v. Sullivan, 922 F.2d 132, 134 (2d Cir. 1990
- Waller v. Waller, 567 So.2d 869 (Ala.Civ.App. 1990). See also, Hudson v. Hudson, 404 So.2d 82 (Ala.Civ.App. 1981). (Alabama Attorney General - FAQ: Marriage/Divorce).
- "Common Law Marriage". Colorado Department of Law. 2008. Retrieved 24 July 2009.
- Graham, Carl O. "Common Law Marriage". Colorado Divorce & Family Law Guide. Black & Graham. Retrieved 24 July 2009.
- TEX. FAM. CODE s. 2.401; Davis v. Davis, 521 S.W.2d 603 (Tex. 1975)
- Hoage v. Murch Bros. Const. Co., 60 App.D.C. 218, 50 F.2d 983 (1931)
- In re Marriage of Winegard, 257 N.W.2d 609, 616 (Iowa 1977)." See Snyder-Murphy v. City of Cedar Rapids (Iowa 2004)
- See In the Matter of the Petition of Lola Pace (Kan. 1999).
- See Snetsinger v. Montana University System, 325 Mont. 148, 104 P.3d 445, quoting In re Ober, 314 Mont. 20, 62 P.3d 1114. See also http://www.LawHelp.org/MT 
- See: NH RSA 457:39 Cohabitation, etc.
- See DeMelo v. Zompa, 844 A.2d 174, 177 (R.I. 2004) (pdf).
- See Tarnowski v. Lieberman, 348 S.C. 616 (S.C. Ct. App. 200)
- Texas informal marriages by declaration require a legally defined form to be completed by both marriage partners and sworn or affirmed in presence of the County Clerk that issues the "Declaration of Informal Marriage." This legally binding document is formally recorded as part of the Official County Records by Volume and Page number. The form is then forwarded by the County Clerk to the Texas Bureau of Vital Statistics where it is again legally recorded as formal evidence of marriage (the same procedure as for a Marriage License). The term "Informal" refers only to the fact that no actual wedding ceremony was conducted. Dissolution of this type marriage requires formal Annulment or Divorce Proceedings, the same as with the other more recognized forms of 'ceremonial' marriages. (Texas Family Code Chapter 24).
- Texas Family Code Sec. 2.401
- See Utah Code Ann. 30-1-4.5 (2004).