How Payment for Order Flow Works: Robinhood, Citadel and You

Payment for order flow is the practice of a market maker paying a retail broker for the right to fill the broker's customers' orders. The broker charges no commission. The wholesaler, such as Citadel Securities, earns the bid–ask spread on the trade and shares part of it with the broker. Options pay the most, because their spreads are wide and the payment is per contract.

Commission-free trading did not make trading free. It changed who pays. In the fourth quarter of 2025, Robinhood earned $314 million from options transactions on 659 million contracts, against $94 million from stocks, by the company's figures. By the third quarter of 2026 its options revenue was $399 million on a record 905 million contracts. Most of that money started as the spread its customers paid.

How does payment for order flow work?

Take a customer who taps "buy" on 100 shares in a broker's app. The broker does not send the order to the New York Stock Exchange. It sends it to a wholesale market maker that has agreed to pay for its order flow.

1. The wholesaler fills the order itself, usually at or slightly better than the best public quote, the national best bid and offer (NBBO).
2. It pays the broker a small amount per share, or per contract for options.
3. It hedges or offsets the position, aiming to end the day flat.
4. It keeps the difference between the spread it captured and what it paid the broker, less its hedging costs and its losses to better-informed traders.

Stock orders can be filled off-exchange from the wholesaler's own inventory. Options are different. A wholesaler that buys an options order guarantees it at a price and sends it into an exchange price-improvement auction, where other firms have a brief chance to beat the guaranteed price. The initiating firm usually keeps a share of the order. The payment to the broker comes either directly or through exchange "marketing fee" programs funded by market makers. The study of US options markets, exchanges, clearing and 0DTE maps the routes.

Some products bypass the system entirely. S&P 500 index options (SPX) trade only on Cboe's exchanges, so there is no wholesaler to sell the order to.

Why do market makers pay for retail orders?

Because retail flow is the most valuable flow to trade against. A market maker's main cost is adverse selection: trading with someone who knows where the price is going in the next few minutes. Retail orders are small, scattered and, on average, uninformed about short-term moves. A wholesaler that knows an order comes from a retail app can quote it a tighter price than an anonymous order on an exchange, pay the broker, and still earn more than it does trading against hedge funds.

The economics reward scale. More flow means better short-term price prediction, which allows tighter quotes, which win more flow. The result is a concentrated industry.

The same paper found that retail options traders favored cheap, short-dated options with an average bid–ask spread of about 12.6% of the option's price (12.3% in an earlier draft), and that they lost money on average.

How much does Robinhood make from payment for order flow?

Robinhood made payment for order flow almost its whole business at first. Its app launched in March 2015 with zero-commission stock trades and added commission-free options in December 2017. In 2020, order-flow payments and transaction rebates were 75% of its revenue, and 81% in the first quarter of 2021, when options brought in $197 million of $522 million, according to its IPO filing as reported.

Company figures; the revenue line includes all options transaction revenue, not only order-flow payments, so the per-contract figure is an approximation.

By 2025 the business had broadened. Net interest revenue was about $1.5 billion of $4.47 billion in total revenue, and event contracts brought in $173 million in the third quarter of 2026. But options remained its largest single transaction line.

Where does a trader's money actually go?

The book follows one stylized trade: a same-day S&P 500 call, about $500 of premium, bought and sold a few hours later at an unchanged midpoint so that every dollar lost is a cost. It compares one SPX contract on Cboe with the same exposure as ten SPY contracts routed through a wholesaler. Fee levels are illustrative assumptions, except the SEC's Section 31 fee; the order-flow payment of $0.45 a contract sits inside the range implied by Robinhood's figures.

Three lessons follow. The spread, not the commission, is the cost: more than nine-tenths of the total on both routes. "Commission-free" says who pays, not whether anyone does: on the SPY route the broker collects $9 of a $20.81 cost without charging anything it calls a commission. And frequency compounds it: the same trade every trading day for a year costs about $5,200 on the cheaper route, for a trader risking $500 a time.

The market maker's $11 is not all profit. It must hedge, pay its own fees and absorb losses to traders who know more. The chapter on following the money works through each step.

Is payment for order flow bad for investors?

The honest answer is that it depends on the product and the alternative. Supporters say retail investors get price improvement and zero commissions. Critics say the improvement is measured against a public quote that may itself be wide, that brokers face a conflict of interest, and that keeping the least informed flow off the exchanges leaves wider spreads for everyone else.

Two regulator cases show where the line has been drawn.

The defensible statements are narrow. The payment is real money that comes out of the spread the customer pays. The price improvement is measured against a public quote. And the business is very concentrated.

Is payment for order flow legal?

In the United States, yes. In December 2022 the SEC proposed an Order Competition Rule, which would have forced most retail stock orders into auctions before a wholesaler could fill them, and a Regulation Best Execution. Both were formally withdrawn in June 2025.

Brokers still owe customers a duty of best execution, and they must publish quarterly Rule 606 reports showing where orders go and what the broker is paid. Those reports are worth reading. They show the routing and the payments, not the price each order would have received elsewhere.

Europe went the other way. The EU's 2024 review of its markets regulation agreed to ban payment for order flow for retail clients, with a transition for member states that allowed it ending on 30 June 2026.

How do other brokers handle order flow?

Not every broker runs the same model. Interactive Brokers offers a Pro routing tier without payment for order flow and a Lite tier with it. Charles Schwab cut online stock commissions to zero in October 2019, alongside TD Ameritrade and E*Trade, and runs thinkorswim for active options traders. On the wholesaler side, Virtu Financial, the one large US market maker with audited public accounts, reported record revenue of $3.63 billion in 2025. The study of market microstructure, order types, spreads and execution explains how order types change what a trader pays: a market order on a wide options quote pays the full spread, while a limit order near the midpoint often fills inside it.

Payment for order flow in the four factors of the edge equation

The Edge Equation judges trading results on four factors that multiply: edge, survival, execution, and discipline and adaptation. Payment for order flow is a story about execution. For the wholesaler, execution is the edge: data, technology, hedging and a cost per trade no individual can match. The companion's catalogue grades retail order-flow internalization B for the firms that do it. For the retail trader, execution is a cost most never price, and buying short-dated out-of-the-money options, the flow that pays brokers most, is graded F for the people who do it.

The broader incentive is plain. A broker paid per contract earns more when customers trade more, and more still when they trade short-dated options. That is the common thread in the Robinhood enforcement cases, and it is why the study of retail trading outcomes finds the gap between what is sold and what the evidence shows widest in this part of the market. For the full map of who earns what, see our guide to how trading firms make money.

The takeaway

Payment for order flow is how commission-free brokers get paid: wholesalers fill retail orders, earn the spread, and pass part of it back to the broker. It is legal in the United States, banned for retail clients in the EU from mid-2026, and most valuable in options, where spreads are wide and the payment is per contract. For a trader, the practical lesson is to price the round trip, spread and fees included, rather than the commission, and to multiply it by the number of trades a year. Chapter 3 of The Edge Equation follows the money through every step of a trade.