what is an execution 
execution is the completion of a buy or sell order for a security the execution of an order occurs when it gets filled not when the investor places it when the investor submits the trade it is sent to a broker who then determines the best way for it to be executed understanding executionbrokers are required by law to give investors the best execution possible the securities and exchange commission sec requires brokers to report the quality of their executions on a stock by stock basis as well as to notify customers who did not have their orders routed for best execution 1 the cost of executing trades has been significantly reduced due to the growth of online brokers many brokers offer their customers a commission rebate if they execute a certain amount of trades or dollar value per month this is particularly important for short term traders where execution costs need to be kept as low as possible if the order placed is a market order or an order which can be converted into a market order relatively quickly then the chances that it will be settled at the desired price are high but there might be instances especially in the case of a large order that is broken down into several small orders when it might be difficult to execute at the best possible price range in such cases an execution risk is introduced into the system the risk refers to the lag between the placement of an order and its settlement 