A couple of things. 1. Even as a sole trader, you should have a business name registered which will give you an ABN. 2. If your annual revenue is $75k+, then you should also be registered for GST. I mention both of these as it will determine the type of document you provide to customers.

Now, for the invoice request, invoices cannot be issued after the order has been paid for. Invoices are only for unpaid orders. We can only provide sales receipts after an order has been paid for. All receipts should itemise the amounts paid by the customer. Here is some more info to guide you:

1. If you are not registered for GST, then you can only ever issue a Sales Receipt.

2. If you are registered for GST, then you should issue a Tax Receipt, which also itemises the included GST amount(s).

3. You can create a Sales/Tax Receipt template in MS Word. Suggest to keep it simple, with your business name, address, ABN, date of issue, and product order details.

4. For FBA orders, you won't have the customer's full address (and you shouldn't ask for it), so just include their name, suburb and state (which is found in their order)

5. For your address, you can just include the suburb, state and postcode if you don't have a PO Box for your business. You don't need to include your name, just your business name.

6. If a customer insists on an invoice, you can simply advise them that invoices are only for unpaid orders, and the ATO instructs businesses to issue a Sales or Tax Receipt for paid orders.

The ATO website has plenty of information about the above and it's worthwhile checking it out.