Depends on the booking engine interface. I typically fly "Y" class. My last corporate travel agent, getting a upgrade before ticketing was not a issue, as the e-invoice would still read "coach". We switched corporate travel agencies, and if I was upgraded before the ticket was issued by AA the e-invoice would read "first", which was not a good thing as it appeared I was purchasing a "F" class ticket. I now wait until ticketing is completed before requesting a upgrade on corporate travel to avoid a challenge to the class of service I was booking.