If you are living together unmarried with the child's other parent, it is best to the parent who is not claiming the child to leave them off completely.
Yes this is confusing and a few of us have been complaining about it for years. There is a special rule where the tax benefits of a dependent can be "shared" between parents who are divorced or separated and live apart. It does not apply to parents who live together unmarried. When Turbotax asks, "is there a legal agreement allowing the other parent to claim the child" you must answer NO if you are living with the other parent, this question only applies to a legal custody arrangement between divorced or separated parents who live apart and share custody. Answering "yes" (thinking that it applies to a verbal agreement between two parents living together) will cause you to file improper tax returns and either claim excess benefits, or fail to claim allowable benefits, or both.
Apparently, the geniuses in marketing think that asking "do you live together unmarried with the child's other parent" is too delicate a question for a tax return.
