Common-Law Marriage in the United States

Common-law marriage is one of those terms that everyone has heard of, but few people actually understand. Because of the nature of modern society, they have become less common than they once were, and now only 11 states and the District of Columbia have provisions for common-law marriages. However, 13 more states recognize such marriages from other states, and consider couples in these relationships to be married (and therefore able to be legally divorced, although this can be a tricky prospect due to the nature of the marriage).
Also called a de facto marriage, these relationships are recognized as marriages even though no legally binding ceremony was performed. At one point in our nation's history, they were quite common amongst pioneers in recently settled areas where there was not necessarily the ability to enter into a traditional, legal marriage. However, because there is no national law governing these marriages, their legality varies from state to state, and though such a relationship may be legally binding in some jurisdictions, they may not be in others.
In order for a relationship to be considered a de facto marriage, several criteria must be met. In general, they are: 

• Both parties in the relationship must consider themselves married. If only one party believes that the relationship constitutes a marriage, then the de facto marriage does not exist.
• Both parties must be of legal age to be married legally.
• Both parties must be qualified to be married in other regards as well, namely being unmarried and of sound mind.
• In many jurisdictions, both parties must hold themselves as married. That means that they must refer to each other as husband and wife, and have been in such a relationship for a considerable amount of time.

If all of these criteria are met, then the couple may be considered to be married, although again only certain states and jurisdictions recognize de facto marriages.
It is also important to understand that while many states may recognize common-law marriages, the IRS does not, and if you are in such a relationship, you will not be able to file as though you were in a regular marriage. If you file taxes as a married couple and you are not, you could be prosecuted for tax fraud.