Payment for order flow (PFOF) is the practice where a broker routes customer orders to a wholesale market maker, and the market maker pays the broker for that flow. It's the engine behind commission-free trading: you don't pay a commission, but your order is a product being sold.

How it works

When you place an order, your broker sends it to a wholesaler who fills it. The wholesaler profits from the bid-ask spread and pays the broker a small amount per share or contract. In exchange, the wholesaler gets a steady stream of retail orders - which are, on average, easier to trade against than institutional flow.

The debate

Supporters say PFOF enables free trading and often provides "price improvement" - fills slightly better than the public quote. Critics argue it creates a conflict: the broker is incentivized to route for its own payment rather than strictly your best execution, and the wholesaler profits from being on the other side of your trade.

If you're not paying a commission, your order flow is the product. That's not sinister - just worth knowing.

What it means for you

For most retail trades in liquid names, the practical impact is small - price improvement often offsets the spread capture. It matters more in less liquid instruments and larger orders, where execution quality can vary. The takeaway: "free" has a mechanism, and understanding it makes you a sharper judge of your fills.