Simply living together does not make a couple common law married in the state of Colorado. You can live together for 100 years and still not be considered common law married. The Court will look at several factors to determine whether or not you and your girlfriend “hold yourselves out as married”. Some of the factors that Colorado courts consider are the following: Do you introduce yourselves as husband and wife? Does your girlfriend use your last name? Do you file joint income tax returns? Do you have joint bank accounts? Do you have joint credit cards? Do you name each other as your spouse on health, life and car insurance policies? Do your friends, family and co-workers consider you husband and wife?