You must send the other party (or their representative) any document that you are required to serve on them.
Generally, you must also send to the other party (or their representative) a copy of any correspondence or document you send to the Commission. If you do not do so, the Commission may forward a copy to the other party (or their representative).
If you are concerned about correspondence or a document being forwarded by the Commission to the other party or their representative (for example, if it contains personal medical details or other confidential information) you should contact the Commission to discuss your options before sending it to the Commission.