Common law marriage—also known as marriage without formalities or informal marriage—is marriage without a wedding or marriage ceremony and without a marriage license. Some states recognize common law marriage under certain circumstances—such as when the parties agree to be married, live together (cohabit) after agreeing to be married, and represent to others that they are married (holding themselves out as a married couple).

Other states previously recognized common law marriages, but no longer recognize such marriages after a certain date on which the law was changed—usually by statute. In other states, common law marriage has not been recognized by the legislature in a statute, but the courts have recognized common law marriage in court opinions or case law.

In Pennsylvania, common law marriage was recognized if it was established before January 1, 2005. Couples who met the criteria for common law marriage by that date are still considered legally married. To have formed a common law marriage in Pennsylvania, the couple must have had the capacity to marry, mutually agreed to be married, and held themselves out to the public as married. This means they would have presented themselves as a married couple in social situations and may have filed joint tax returns or used the same last name. However, Pennsylvania abolished common law marriage prospectively from January 1, 2005, with the passage of Act 144 of 2004. This means that no new common law marriages can be formed in Pennsylvania after that date. For individuals claiming a common law marriage established before 2005, legal issues can be complex, and it is often necessary to consult an attorney to navigate the associated legal challenges.