if they've admitted in a post that they have another account, just report that post.

if it's just a suspicion you have, send a PM to a mod - a smod or admin, someone like FrenchyFungus or carmel_l, would be a good choice - with the reason why you think they are a multi, and any relevant proof/links.
from daylight...
...into darkness
Quote by 100%guitarmad
I'm not new or anything, but is there anyone that you can report multis to?
you don't have to be new to start a thread in this forum.
it's for discussions of how to use the UG forum and profile system.
appropriate question.
right placement.
good thread.
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.