Common law marriage in Colorado does not have the above formalities and is not recognized by any statute.  However, case law has recognized that parties can become married simply by their actions, even if they never apply for any marriage license. These actions must show that the parties mutually agreed to a marital relationship.  Now usually, the issue of a common law
marriage does not come up until one of the parties wants a “divorce” and the other party disagrees that they were ever married. 

So evidence of a mutual agreement to be married is very important to establishing that a common law marriage exists.  In Colorado, there must be conduct showing a mutual public acknowledgement of the marital relationship to establish a common law marriage.  The reason for the public display requirement is to guard against fraudulent claims of common law marriage. Public acknowledgement of the marital relationship can be shown in part by cohabitation, but more is needed; particularly in this day and age where cohabitation is not taboo as it once was.  There must be a general understanding or reputation among persons in the community in which the couple lives that the parties hold themselves out as husband and wife. Specific behavior that may be considered includes joint bank and/or credit card accounts held in each other’s names; purchase and joint ownership
of property; the use of the man’s surname by the woman (or vice versa); the use of the man’s surname by children born to the parties; and the filing of joint tax returns.  There is no specific form that this evidence must take, but rather any evidence to show that the parties openly manifested their desire to be husband and wife will suffice.