Any customers who are seeking to use Australia us Post services simply needs to complete the API Key Registration form on the Developer Centre.
Please note that you will require an active parcel contract with Australia Post in order to complete this form. The customer account number that is provided will be validated by this form and if there is no active parcel contract then the customer will be unable to complete this step.
Here, the you will be required to login in order to complete the form and will be asked to supply Australia Post with their eParcel account number/s. Once completed, the customer will be asked whether they will be accessing the API via a Platform Partner, to which they must answer "Yes".