I named my daughter my last name. Dad is not my husband. He wants to change her name to his. Can he do this w/out my knowledge?he does pay child support and keeps up with visitations. He however didn't get his name on the because within the specified amount of time he had with court order. We both reside in Texas

He can not do it without your knowledge, he would have to go though court and get a court order for it

Also if the courts have declared him the legal father then it doesn't matter if his name is on the borth certificate or not. As Fr_Chuck has said he can't without your approval and must go through the courts to do it.