My DH gets quarterly bonuses. It all appears on his group certificate & he gets taxed a s&@tload on bonus money. When it comes in we work out together what to put it towards: usually a couple hundred for him to blow on man stuff & the rest goes towards holidays or large purchases.
However, his work also sometimes offers sales incentives in the form of prepaid Visa cards. Usually $50 or $100, but once he got one for $700. So if the bonus was given as gift cards it would be like cash I guess? Anyways they don't show up on tax stuff. I don't see how you could track it. I would be totally fine with DH spending these entirely on himself, he earned it!