If you've used any exploits to gather vast amounts of money over the course of your adventures, you'll be approached by a character named the Taxman. This rather prim and proper man will question Geralt about the Witcher's income, and will even refer to the various coin farming tricks that players have been discovering and using since the title launched back in May.
Apparently, if your questionable practices are found out, the Taxman will impose a fine and you'll have no choice but to pay up. If you've been a good little monster slayer, though, you'll actually be given a nice reward. The system works, we suppose.
The whole thing's another fantastic example of the developer's devotion to detail and the understanding of its fans.