Ok, so I just lodged an article at the PO with Parcel Post and SOD. This is what I got:

Online TaT atm (feel free to look it up):

63310336154063

So, you'll see exactly what you and the customer will now see. It's not your C&S account.

The receipt for this shows the following:

Australia Post

Post Office Name - Post Code

Parcel Post - Cost $6.95

Article ID

63310336154063

PP SoD LBL x1 $2.95

Total

Cash tendered

Change

GST etc

ABN Tax Invoice etc

(Myself and the PO lady lol'd hard at the next part when we were inspecting the receipt):

'Use Registered Post if extra cover against loss or damage is required'

Date  - some codes - time

Advertising about new parcels and tracking

The helpful lady then stuck the senders copy of the parcel post label on the back of my receipt.