Originally Posted by
MSPeconomist
Some employers also demand boarding passes for reimbursement. If you upfare the ticket, you'll get a new ticket number which will show on the boarding pass and not match the original coach ticket number on the original coach receipt that you apparently plan to submit. This will make clear that you did not get a free upgrade based on FF status.
I've sometimes had to explain the different ticket numbers when I use miles to upgrade the ticket. (My employer requires submission of all boarding passes for reimbbursement.)
This seems a bit of a stretch given how many things can drive a new ticket number / reissuing of the ticket, many of which don't even change the fare or class of service or ticket value. And this is also along with the fact that now so many people don't even use paper boarding passes but rather mobile boarding passes, which don't even display the confirmation number, never mind the ticket number.