What Free Trading Was Actually Charging You

The marketing pitch was simple. Trading should be free. The legacy brokerages had been charging seven to ten dollars per trade to retail customers for decades, an obvious anachronism in a fully electronic market. Robinhood, launched in 2013, would charge nothing. The interface would be a phone app. The user would tap to buy, tap to sell, and never see a commission line. The friction would disappear. The democratization of finance would follow.

The model worked. By 2024, Robinhood had over twenty-three million funded customer accounts, hundreds of billions of dollars in custodied assets, and a market capitalization that had at one point exceeded sixty billion dollars. The legacy brokerages, watching the customer flow drain away, were forced to eliminate their own commissions in 2019 — a Schwab announcement followed within hours by E*Trade, TD Ameritrade, and Fidelity. The era of paid trading ended. The era of free trading began.

The question worth asking, on the question of who actually paid for the free trading, is more complicated than the slogan implied.

The Payment-for-Order-Flow Machine. Robinhood's primary revenue source for most of its history has not been commissions. It has been a practice called Payment for Order Flow — abbreviated PFOF — in which the brokerage routes its customers' trade orders to specific market makers (Citadel Securities, Virtu Financial, Susquehanna) who pay Robinhood a small per-share fee for the right to execute those orders against their own inventory. The market maker, in turn, fills the customer order at a price slightly less favorable than what would have been obtained on the open exchange — by fractions of a cent per share, but multiplied across billions of shares annually.

The math, in aggregate, is large. In 2021 — a peak year — Robinhood earned approximately one billion dollars in PFOF revenue. The customer who placed an order to buy 100 shares of a popular stock might receive an execution at $50.005 when the prevailing exchange best offer was $50.00 — a half-cent of disadvantage, fifty cents on the trade. Multiplied across millions of customers and billions of trades, the half-cent became Robinhood's revenue and the market maker's spread.

The Marketing Truth. It is important to be precise here. PFOF is legal. It is disclosed (in the small print of the brokerage agreement). The market makers do not always fill customer orders worse than the exchange would; in many cases, particularly for less liquid securities, they fill better. The aggregate cost to the customer is genuinely difficult to estimate and has been the subject of repeated regulatory studies that have arrived at different numbers depending on methodology.

What is also true is that "trading is free" is not, strictly, the description of the transaction the customer is participating in. The customer is paying a small, invisible execution-quality premium per trade in exchange for the absence of a visible commission. The premium is, in many cases, smaller than the commission would have been. For some customers, particularly high-frequency traders and those moving through illiquid securities, the premium is larger. The accounting honesty would have been to call the model "trading at low all-in cost, in exchange for slightly worse execution quality, with cost paid implicitly through the bid-ask spread." This would have been accurate. It would also have been a worse pitch.

The Regulatory Question. The Securities and Exchange Commission has, in recent years, considered banning PFOF outright on the grounds that it creates structural conflicts of interest between the brokerage (which wants to maximize routing payments) and the customer (who wants best execution). The European Union has moved further in this direction. The United Kingdom has banned PFOF for retail trades. Robinhood, in response, has diversified its revenue base into interest income on customer cash balances, margin lending, premium subscription services, and crypto trading fees — all of which have grown materially. The company is no longer dependent on PFOF in the way it once was. But the model that built it, the free-trading slogan that drove the customer acquisition, was built on a particular kind of accounting opacity.

The lesson, which the next generation of consumer financial services is now slowly learning, is that there is no such thing as a free product in a regulated financial system. The cost is paid somewhere. If it is not paid in commission, it is paid in spread; if not in spread, then in float; if not in float, then in data; if not in data, then in upsell. Free is always shorthand for "paid in a category the customer is not currently looking at." Robinhood was, in this respect, neither a fraud nor a victim of misunderstanding. It was an unusually elegant exercise in moving the customer's attention from one line on the receipt to another, smaller, less visible line — until the regulators started looking at the smaller line, which is what regulators eventually do.