Answer
When creating a direct entry payment file, or processing super, you may be prompted for a User ID / APCA Code. This value is stored on each company bank account under Company >> Bank Account.
This is always a six-digit number.
For most major banks (ANZ, Westpac, NAB) it is six zeroes (000000). For CBA it is 301500. For any other financial institution you will need to contact them and ask for your Direct Entry User ID, also known as an APCA ID.