But regulators have expressed some trepidation about broker payment systems. While they have not banned payment for order flow, regulators have called into question whether it presents conflicts of interest in how retail brokers route their customers’ trades. They’ve also warned about how brokers price customer orders, and differences between the fastest, priciest data feeds and their slower-moving counterparts. The U.S. Securities and Exchange Commission asked a committee of advisers whether the systems should be banned or altered — but hasn’t taken any steps yet to change the practice. Regulators are also taking a broader look at how individual investors’ trades get carried out. The SEC fined Citadel Securities $22.6 million in January, saying the firm inaccurately described how it handled trades placed by small investors.

https://www.bloomberg.com/quicktake/payment-for-order-flow