Best execution

Best execution refers to the duty of an investment services firm (such as a stock broker) executing orders on behalf of customers to ensure the best execution possible for their customers' orders. Some of the factors the broker must consider when seeking best execution of their customers' orders include: the opportunity to get a better price than what Is currently quoted, and the likelihood and speed of execution.

In Europe, there has been an attempt to define "best execution" within the Markets in Financial Instruments Directive (MiFID), which introduces the principle that, when carrying out transactions on their clients' behalf, "investment firms [shall] take all sufficient steps to obtain, when executing orders, the best possible result for their clients taking into account price, costs, speed, likelihood of execution and settlement, size, nature or any other consideration relevant to the execution of the order. Nevertheless, where there is a specific instruction from the client the investment firm shall execute the order following the specific instruction." MiFID II. Article 27 "Obligation to execute orders on terms most favourable to the client"

For most broker-dealers or execution agents, best executions are usually optimally constructed via either static or dynamic programming.