Like true ECN brokers, STP brokers don’t have a dealing desk, but they employ some of the practices of Market Maker brokers in order to provide more flexible trading conditions to their clientele and bypass some of the limitations of trading exclusively within the interbank market.
Most of the time, this type of broker displays price rates that are identical to the interbank market rates, and as a first priority, STP brokers process trades directly in the interbank market just like an ECN broker. However, when a counterparty for an order cannot be found in the interbank market the STP broker may choose to act like a Market Maker and match the order within its own client base or take up the counterparty of the order itself.