<prompt> Human: So my girl and I have a 2 year old child, we both are the biological parents and we all live in the same place we rent. question is should each of us file as Single or file as Married. please help  <response>: If youre not married, you cant file as married. There is no common law marriage in Washington, though if there was, its a much bigger step than just filing your taxes together. Its getting married. 