What do I need to file to be placed on my 12-year old son's CD? The bank says I need court documents, isn't a birth certificate and ID enough?

It is difficult to understand the context of your question. Apparently your minor child already has a CD issued by a bank. Since he is a minor, some person other than you -- another adult -- must be the actual "owner" of the CD, in trust (under the Uniform Transfers to Minors Act or otherwise) for your son. You need the consent of that person to be substituted or added to the account as an account owner. If somehow the CD was erroneously issued in your son's name alone, you will need a court order appointing you as custodian of this account.