Fee schedules are formulas in a simplified language (a modified version of the PHP programming language) that specify how much to charge or rebate for specific trading activity.
For each direct fee category (Commission, Exchange, NSCC, Clearing, TAF, SEC, and Misc) there can be one schedule in effect at a time but different schedules can be in effect for different accounts.
There are four formula types: "Per Execution," "Per Order," "Per Symbol" and "Fee Rules."