You can see the fees here. Honestly in the grand scheme of things, the most important part is just that being a professional user automatically puts you in the crosshairs for non-display fees, so that's the part I'd be most cautious about. Another thing people don't realize is that licensing is still very much an honor system. Exchanges simply don't have enough manpower or the means to chase down individual pros/non-pros. Most of them treat lost revenue from license misclassification as a cost of doing business for them. There's also a lot of edge cases that even their own heads of market data sales can't classify off the top of their head. Most of these rules are in place more so that they can go to a big shop with many analysts, like Fidelity or State Street, and audit them one time for some $10^5 to $10^6+ in pocket change. It's also so much easier for them to look at their users who're managing their own iLinks, or look at their internal volume leaderboard, and go down the list to see who's underpaying on non-display fees than to go through the list of non-professional individuals. So, FWIW, if you feel you're a bona fide non-professional user, there's a good chance you are, and if you feel misclassified, it doesn't hurt to speak to your broker, ISV or data provider (*wink*, if you need a data provider who knows what they're doing...), whoever's responsible for entitlements, to get it resolved.