Implementing a check-off can't be too hard. Over on IV posters have to choose whether each post is OT, GN or TA before submitting msg. A simple "Have you veen compensated in any way for this stock" (or something similar) with just a yes or no check-off might work. If they said "no" and it turned out to be proven "yes" at least there'd be a record.
Back in ancient days, the Druids thought black cats were human beings.