If you paid on our website – just log into your account where you will find tax invoices for purchases.
Australian Customers: The tax invoice generated has everything needed by the ATO for sales less than $1000 as described here:
https://www.ato.gov.au/Business/GST/Issuing-tax-invoices/
If you paid in the OzRunways → Settings menu, this is an Apple in-app purchase. That is a transaction between yourself and Apple, who collect and pay the GST. They also issue the invoices. If you paid this way, then Apple normally email you a receipt a few days after. We cannot issue tax invoices for these. This article may be helpful: https://support.apple.com/en-au/HT204088