I booked my daughter as a UM on a flight this November. I paid the $50 fee up front for the first time (typically I prefer to pay at the airport, since the fee is apparently non-refundable or non-transferable if I need to change her flight but the website won't allow this any longer).

Anyway, I received the email confirmation and receipt and the $50 fee is nowhere to be found. While I have some concern that I have zero proof that I paid this fee should I be asked to pay it at the airport, I really don't expect that to be an issue as the reservation clearly identifies her as a UM. I am somewhat bothered that any merchant would require me to pay for something and then not provide me with any record that I did so. Even looking up her reservation at the WN website shows nothing about the $50 fee payment.

Because the fee is charged separately from the fare (my card was charged $150 + $50, not a single $200 charge), I think WN should provide a receipt.

By comparison, I booked her outbound on United and the email containing the reservation has a section for airfare paid plus a section for the $99 UM fee.