Receipts are issued automatically after the completion of your booking.
If you need an invoice, select "I would like an invoice instead" at the final step of the booking process, before making the payment. Then, fill in all the mandatory fields shown in the image below:
Figure 1: Invoice Request
You can find your receipts and invoices in "My Booking", under the "Check your booking details" section. Click on the "Ticket receipt" link to download them. Please note that invoices may not be available immediately and usually appear in "My booking" within one day. Both receipts and invoices will appear as "Ticket Receipt".
Figure 2: Receipt/Invoice Download