This is more just a warning about an apparent glitch in the SWU reservation process. I tried searching, but SWU yields 1000s of threads, and void is equally usless.

So, here's my story: I booked a last minute trip to europe last thursday through my corporate travel agent and as soon as it was ticketed, requested upgrades both directions using SWUs. The result was as expected, two SWUs reserved. The next day, I realized that the TA had booked the outbound for the wrong day (all fully refundable B fares). When I called the TA back, they voided the trip and issued a new ticket. This, of course, still showed the same record locater in UAs system. For some reason, the united systems showed two outbound flights for the same record (both ticketed). I again went in and requested an upgrade on united.bomb. The result? Three SWUs now reserved. I wasn't worried about this as I figured that when the incorrect outbound flight was cleared out of UAs system, I would get my SWU back. No such luck. When I called Sunday morning to get the record cleared up (United was still showing the correctly voided ticket on the PNR), the extra flights disappeared, but so did my third SWU! I called MP and the only way the helpful agent could verify this was by looking at my entire years history of deposits/redemptions of SWUs. There was no reservation of the "missing" SWU and it didn't show as redeemed. So now some group at United is supposedly looking into this (the E-Upgrade audit team or some such group).

The moral of the story, if you have an upgrade applied to a ticket that you plan to void, call and remove the upgrade before you call to void the ticket.