May I ask if the air ticket invoice can be issued?

Hello, when you book a ticket, you can choose to mail the reimbursement voucher and fill in the address. The invoice will be sent to you within 10 working days after your itinerary is completed. If you forgot to choose when you bought the ticket, you can contact customer service to have a look How to deal with it.

The itinerary is used as a proof of reimbursement.