If you want to sell digital products (subscriptions or single issue purchases) in your iOS apps, you will need to ensure you have agreed to the correct contracts in the "Agreements, Tax, and Banking" section in your iTunes Connect account.
You will need to ensure you have filled out your contact info, bank info and tax info. Download the tax agreement from this page for more information.
Everyone, whether you are a business located in the United States or not, will need to set up a U.S. tax form.
Australian businesses will also need to set up an Australian tax form.
For more information about agreements, tax, and banking for iOS apps, please refer to this page.