I think he is trying to tell you the way IT dept audits this kind of stuff, all they are interested in is why you made a purchase and to whom. They are not interested in other info about the spend. So in theory if you play your cards right, you won't have to give anything in taxes.
@Tejo however, since he is transferring money to his account (most likely) and credit card spends on the other side are counted as income, I wonder if his liability would be much more than just the cashback. Is there a way to tell IT dept that they were just rotating money and thus spends cancel each other out, Only benefit is cashback that they earn? I don't think there is .