What Is Payment for Order Flow? How Free Trading Works

Payment for order flow (PFOF) is the practice where your broker routes your stock orders to a market maker — who pays the broker a small fee (typically fractions of a penny per share) in exchange for the right to execute your trade. This is how brokers like Robinhood, Schwab, and Fidelity offer commission-free trading: they earn revenue from market makers instead of charging you directly. It's one of the most debated practices in modern market structure.

How PFOF Works

When you submit a buy order for 100 shares through your broker, your order doesn't necessarily go to the NYSE or Nasdaq. Instead, the broker routes it to a wholesale market maker — typically Citadel Securities or Virtu Financial — who executes the trade. The market maker pays the broker perhaps $0.002 per share (20 cents total on your 100-share order) for the privilege.

The market maker profits by executing your order at a price slightly better than the public exchange quote and capturing the difference. If the exchange quote is $100.00 bid / $100.02 ask, the market maker might fill your buy at $100.01 — giving you a $0.01 improvement over the exchange ask while keeping $0.01 for themselves. Both sides benefit: you get a slightly better price, and the market maker earns a small spread.

The Controversy

PFOF critics argue that it creates a conflict of interest: brokers route orders to the market maker that pays them the most, not necessarily the one that gives you the best price. The broker's customer is supposed to be you, but their revenue comes from the market maker — potentially misaligning incentives.

The GameStop episode intensified scrutiny when Robinhood restricted trading in GameStop and other meme stocks during the squeeze. Critics alleged (though Robinhood denied) that the restrictions were influenced by Citadel Securities (Robinhood's largest PFOF source) and Citadel LLC (which had invested in Melvin Capital, a hedge fund losing money on GameStop short positions). The connection between PFOF revenue and trading restrictions raised questions about whose interests the system serves.

PFOF defenders argue that it enables commission-free trading (saving retail investors billions annually in commissions), provides price improvement over exchange quotes (documented by execution quality reports), and that the alternative — charging commissions — would cost investors far more than any theoretical PFOF-related price disadvantage.

What It Means for Quality Investors

For long-term quality investors, PFOF is a non-issue in practical terms. The price improvement or disadvantage is measured in fractions of a penny per share — completely immaterial for investors holding positions for years. The elimination of commissions (which PFOF revenue enabled) saves far more than any theoretical PFOF cost.

If you're trading 100 shares of a $150 stock to hold for five years, whether you paid $150.01 or $150.02 has zero meaningful impact on your return. The business quality, competitive moat, and valuation gap are what determine whether your investment returns 50% or 150% over those five years — not the microstructure of order execution. For large orders in illiquid stocks, the price impact from PFOF routing can be meaningful — in those cases, a direct-access broker may be worth the commission. The limitation to be aware of: for large orders in illiquid stocks, PFOF routing can result in meaningfully worse execution. In those cases, a direct-access broker may be worth the commission.