Some international destinations require additional copies of the international labels to be affixed to the package in a clear plastic document envelope. These are then removed by customs. If more than one label is generated, affix one label directly to the package and place any additional labels in a clear plastic document envelope and affix that to the parcel separately.
1 copy of CN23 is required to these 12 destinations:
Canada
Hong Kong
Israel
New Zealand
Norway
Poland
Singapore
Spain
Switzerland
United Kingdom
United States
Vietnam
4 copies of CN23 is required to India, Turkey and all destinations listed in Zone 9.
All other destinations will require 2 copies of CN23.
Until recently these labels would have been generated on the larger A5 CN23 labels which also had instructions printed on them down the right side of the label such as "Customs Copy" etc.
Since AusPost changed these to the smaller A6 CN23 label they have removed those instructions but they are still required. We've raised that as an issue with AusPost and they are looking in to whether it can be added back on to the label.