Abstract: A computerized method of monitoring compliance comprises: (a) receiving information regarding an order for a financial instrument which was executed at a first one of a plurality of automated trading centers against a protected quotation of said first trading center, the information including at least an order time at which the order was placed, an identifier sufficient to identify said financial instrument, a volume of the order, an identifier sufficient to identify said first trading center; and a price of the order; (b) receiving market data for said financial instrument, said market data including each protected quotation for the financial instrument at each of the plurality of automated trading centers during a grace period extending from a second time, which is prior to said order time, to said order time; (c) comparing said protected quotation of said first trading center at the order time to each other protected quotation for the financial instrument at the order time, and: (1) if none of the other pr