It is very important that, when both parents live together unmarried, one parent claim the child as a dependent and answer "no" to the question, "do you have a custody agreement with the other parent?" This question only applies to parents who live apart and share custody. The parent who will not claim the child as a dependent should not even list the child on their return at all.
Doing something different can sometimes cause problems because of how turbotax asks certain questions to determine dependent type, and how sometimes parents misinterpret the questions.
