I want to legally change my daughters last name to my fiance's last name. Her biological father hasn't been in her life or tried to since she's been born. I gave my child his last name because I thought he was going to take part of her life. Do I have to seek her real father's permission to change her name even if he's not on the birth certificate? My fiance's name is already on her birth certificate

Contact your local courthouse and ask what needs to be done to file a name change. I think it depends on your state, but here you would not have to contact her birth father.