An agency debit memo (ADM) is a notice sent, normally by an airline to a travel agent, requiring the recipient to pay a sum of money to the sender. A frequent reason for issue of an ADM is where an air travel ticket has been issued and its rules have not been fully complied with, such as where the fare rules require tickets to be issued within three days of creating the PNR or reservation, and the ticket was issued on the fifth day. Other reasons can include: -Holding a seat on a flight, even after the airline has cancelled your space, and not removing it before the aircraft departs.