If you send an item 5kg or under in Australia using the Australia Post flat rate packaging range, postage is based on the size of the package, rather than the weight and destination.
There is a wide range of Australia Post-branded packaging eligible for flat rate postage:
Prepaid satchels
Flat rate satchels
Mailing boxes
Padded mailers
Tough bags
Mailing tubes
AusPost have broken it into extra small, small, medium, large and extra large sizes. Only packaging listed in these Flat Rate Packaging links are eligible to be used with Flat Rate pricing.
There are multiple Flat Rate Boxes/Tubes for each size. The dimensions we display are the just the standard ones, but you can use any flat rate package from their list of inclusions in the size links above.
You must select the relevant Flat Rate Package size from the dropdown list in the Packages column of the order in ReadyToShip for Flat Rate pricing to appear.
We don't submit the dimensions when Flat Rate packages are used, we just submit the size you have chosen, eg. Flat Rate Large
For example, you just need to choose the Large Flat Rate box that is preloaded in our system so you get the Flat Rate pricing, even if you are using the BX24 box. Don't enter your own dimensions, or you will be charged at custom packaging rates.
Note: Flat Rate Packaging and postage are charged separately. Shipping costs are not included in the packaging price.