The cost of 'free' trading: understanding PFOF and hidden spreads

While commission-free trading has lowered the barrier to entry for retail investors, it is often funded by Payment for Order Flow (PFOF), where brokers receive fees from market makers to route trades through them. This model can lead to hidden costs in the form of wider bid-ask spreads and inferior execution quality. In 2026, the regulatory landscape is shifting, with the UK's FCA already banning the practice and the EU phasing it out, while it remains legal but strictly disclosed in the US via SEC Rule 606.

The brokerage industry has undergone a radical shift toward commission-free trading. While this has removed the entry barrier for millions of retail investors, it has also obscured the true cost of participating in the markets. Revenue models have transitioned from transparent transaction fees to complex, behind-the-scenes arrangements. We examine the mechanics of Payment for Order Flow (PFOF) and how hidden spreads impact your bottom line.

Payment for Order Flow (PFOF): The Engine of 'Free'

When you place a trade with a commission-free broker, the broker often does not send that order directly to a public exchange like the NYSE. Instead, they route the order to a 'wholesale market maker' (such as Citadel Securities or Virtu Financial).

• The Incentive: The market maker pays the broker a small fee (a fraction of a cent per share) for the privilege of executing that order. This is Payment for Order Flow.
• The Market Maker's Gain: Market makers profit from the 'bid-ask spread'—the difference between the price at which they buy and sell a stock. By receiving a constant stream of retail orders, they can manage their inventory and capture this spread with minimal risk.
• The Conflict: A potential conflict of interest arises because the broker may be incentivized to route orders to the market maker that pays the highest PFOF, rather than the one providing the best execution price for the client.

The Impact of Spreads and Execution Quality

For a retail investor, the most significant 'hidden' cost is not the commission, but the 'slippage' caused by wider spreads and inferior execution.

1. Price Improvement: In a transparent market, a broker should strive for 'Price Improvement'—getting you a better price than the current best bid or offer. PFOF-reliant brokers may offer less price improvement than those that charge a commission and route to public exchanges.
2. Wide Spreads: On low-liquidity stocks or during periods of high volatility, the bid-ask spread can widen significantly. If a 'free' broker fills your order at the far end of a wide spread, you could lose more in price inefficiency than you would have paid in a $5 commission.
3. The 'Small Trade' Illusion: For an investor buying 5 shares of a $100 stock, a $5 commission is a 1% cost—which is high. In this case, 'free' trading is genuinely beneficial. However, for a trader buying 500 shares, a hidden spread of just $0.02 per share costs $10—making the 'free' trade twice as expensive as a fixed commission.

Regulatory Landscape: UK and EU vs. USA

Based on stances from the FCA and ESMA, The regulatory approach to PFOF varies significantly by jurisdiction, reflecting different views on market fairness:

• USA: PFOF is legal and widely used by almost all major retail brokers (Robinhood, Charles Schwab, E*Trade). The SEC requires 'Rule 606' disclosures where brokers must reveal their PFOF revenue, but the practice remains central to the US retail ecosystem.
• United Kingdom (FCA): The FCA has effectively banned PFOF, arguing that it is incompatible with the broker's duty to provide 'Best Execution.' As a result, UK brokers typically charge transparent commissions.
• European Union (ESMA): The EU is in the process of phasing out PFOF across all member states by 2026, aiming to create a more transparent and unified capital market.

How to evaluate your broker's true cost

To understand what you are actually paying, you should look beyond the commission headline:

• Check the Spread: Compare the price offered by your broker with a neutral data source (like Yahoo Finance or a Tier-1 platform) at the exact moment of trade.
• Review 'Rule 606' Reports: If you are in the US, look for your broker's quarterly SEC disclosures to see how much they earn from market makers.
• Assess Asset Classes: PFOF is most prevalent in stocks and options. In Forex and Crypto, the 'hidden cost' is almost entirely in the spread markup, which can be massive on 'free' platforms.

We recommend that active traders and those with larger portfolios prioritize brokers that offer direct market access (DMA) and transparent commission structures. For small, long-term investors, commission-free platforms remain a valuable tool, provided the user understands that 'free' is a marketing term, not a financial reality.