Colorado law recognizes the doctrine of common law marriage between a man and a woman [there is no such thing as same-sex common law marriage in Colorado law].
There are many misconceptions about what does or does not make a common law marriage. The most important factors in whether a common law marriage has been created are (1) whether the parties intended to be married and (2) whether they have lived together. Other factors are really just ways of proving whether the parties did or did not consider themselves to be married. Examples of behavior which might show this intention to be married include filing joint tax returns, owning property together, joint bank accounts, wearing wedding rings, etc. The decision is usually based on a combination of one or more of these or other factors.
A common law marriage is simply an alternative route to getting married instead of obtaining a civil marriage license. There is no such thing as common law divorce. If a common law marriage has been formed, the only way to obtain a divorce is to file for dissolution of marriage through the court system.
If you have created a common law marriage, there can be enormous future consequences which may not be clear at the time of separation. The existence of a common law marriage may impact the ability to inherit property or receive life insurance proceeds; as well as other financial obligations such as maintenance and division of marital property. For these reasons, if there is any doubt as to whether one has entered a common law marriage, it is very wise to consult with a lawyer at the time a relationship ends. A mistake in assuming there is no common law marriage can have devastating lifelong consequences.