The Duffel Balance is a simple prepaid account. You top up your balance using a credit/debit card or bank transfer, and then you can spend that money through Duffel on flights and paid extras.
Unfortunately, we aren't able to issue invoices for top-ups.
When you top up, you haven't actually bought any services from us yet, so there are no services for us to invoice for.
Your top up sits in your Duffel account waiting for you to spend it on services (that is, flights) - you can see it by clicking "Balance" on your Duffel dashboard.
You can download a PDF statement from the "Balance" page in your Duffel account. The statement is your financial record, showing your top-ups, the money you've spent (that is, flights you've booked) and the money you've received (that is, refunds you've got back from airline).
An example statement is attached - the address in the top-left corner will be your address, not Duffel's.