If you live together and share custody, one parent gets to claim the child and all tax benefits and the other parent can't claim anything. The parent who is not going to claim the child should remove the child from their tax return completely, delete them from the dependent screen.
The parent who is going to claim the child should review how they answered the questions -- if they answered that they will share the dependent with the other parent, then they probably did not claim full benefits, and might get more back if they amended and changed their answers.
But we can't see your actual tax files. You would need to post more details about your personal situation.
