Remember, you don't have to achieve best execution but you should seek it. As a 2001 speech
by former OCIE Director Lori Richards
makes clear, this is a legal obligation - stemming from your fiduciary duty to your client. She said advisers are "required to 'periodically and systematically' evaluate the quality of execution services received from the broker-dealers that are used to execute fund trades."
Where an adviser has responsibility to direct client brokerage, it has an obligation to seek best execution of clients’ securities transactions. In meeting this obligation, an adviser must seek to obtain the execution of transactions for clients in such a manner that the client’s total cost or proceeds in each transaction is the most favorable under the circumstances. In assessing whether this standard is met, an adviser should consider the full range and quality of a broker’s services when placing brokerage, including, among other things, execution capability, commission rate, financial responsibility, responsiveness to the adviser, and the value of any research provided.