When sending an item weighing 5 kg or less within Australia using eligible Australia Post Flat Rate Packaging, postage is calculated based on the package size, not its weight or destination.
Eligible packaging
Australia Post offers several types of packaging eligible for flat rate postage:
Prepaid satchels
Flat Rate satchels
Mailing boxes
Padded mailers
Tough bags
Mailing tubes
Packaging is grouped into five sizes:
Only the packaging listed on these Australia Post Flat Rate Packaging pages is eligible for flat rate pricing.
Selecting a Flat Rate package in ReadyToShip
Each size can include multiple boxes, satchels or tubes. ReadyToShip displays the standard dimensions for each size, but you can use any eligible package listed by Australia Post for that size.
To receive flat rate pricing, select the relevant Flat Rate Package size from the dropdown menu in the order’s Packages column.
When you select a Flat Rate package, ReadyToShip sends the chosen package size to Australia Post - such as Flat Rate Large - rather than its dimensions.
For example, if you are using a BX24 box, select the preloaded Large Flat Rate package in ReadyToShip. Do not enter the box dimensions manually, as Australia Post will then calculate postage using custom packaging rates.
Note: Flat Rate Packaging and postage are charged separately. The packaging purchase price does not include postage.