Payment for order flow

What it means

When a customer submits a stock order, the broker decides where to route it for execution. Under a payment-for-order-flow (PFOF) arrangement, a market maker or other trading venue pays the broker for directing eligible orders its way. The payment goes to the broker, not automatically to the customer.

A venue may seek customer orders because it can execute them against its own inventory or otherwise handle the trading interest. Receiving a routing payment creates a potential conflict of interest: the broker has a financial reason to select a paying venue. That does not, by itself, establish whether a particular customer received a good or bad execution. Execution quality must be assessed separately.

How it is calculated

A simple way to express a per-share stock-order payment is PFOF payment (US$) = executed shares × payment rate (US$ per share).

• Executed shares is the number of shares filled under the arrangement, not necessarily the number originally submitted.
• Payment rate is the amount the venue pays the broker for each executed share, in US$ per share.
• PFOF payment is the resulting broker revenue attributable to those fills, in US$.

Actual arrangements can use different rates or terms. The formula describes the payment, not a charge that can be assumed to appear on the customer’s statement. It also does not calculate the customer’s execution cost. To examine that cost, compare fill prices with an appropriate reference price and consider factors such as spread, price improvement, fees and market impact.

Worked example

The following numbers are hypothetical and simplified:

1. A customer submits an order for 100 shares. All 100 shares execute at a venue that pays the broker US$0.002 per executed share.
2. The broker’s payment is 100 shares × US$0.002/share = US$0.20.
3. Suppose the best displayed offer immediately before a buy execution is US$50.02, and the customer fills at US$50.01. Relative to that offer, the fill is US$0.01 per share better, or 100 × US$0.01 = US$1.00 in hypothetical price improvement.

The US$0.20 broker payment and US$1.00 customer price improvement measure different things; neither should be subtracted from the other as if they were the same type of cost. This single fill cannot establish whether another available venue would have produced a better overall execution. The quote used for comparison, the time of the fill, execution speed and the chance of a fill also matter.

Why it matters before you trade

PFOF is relevant when evaluating how a broker handles orders, particularly marketable orders that can execute immediately. A zero-commission trade can still have execution costs: a buy may fill above the midpoint of the bid-ask spread, for example. Conversely, the presence of PFOF does not prove that the customer paid more than they would have elsewhere.

Before placing an order, distinguish broker routing incentives from observable execution terms. Useful questions include what routing and execution-quality information the broker makes available, whether the order can receive price improvement, and how order type and execution conditions affect the possible fill. A limit price controls the worst permitted purchase or sale price, but it does not guarantee an execution.

How PreTrAIde uses it

PreTrAIde’s stated quantitative layer does not identify PFOF arrangements or calculate broker routing payments. Its pre-trade analysis estimates factors such as the bid-ask spread, participation in daily volume and market impact for a proposed stock basket. Those estimates help frame potential execution costs before an order is placed; they cannot determine how a particular broker will route or fill it.

PreTrAIde is analysis software, not a broker. It never receives, transmits or executes an order; users place trades themselves through their own broker. Its GO, NO-GO and MODIFY verdicts are decision support, not recommendations or a measure of a broker’s PFOF practices.

Common mistakes

• Equating PFOF with a customer fee: The venue pays the broker; the customer’s execution costs require separate analysis.
• Assuming a payment determines the best fill: A routing incentive alone does not reveal the price, speed or likelihood of execution.
• Treating price improvement as a complete comparison: Improvement relative to a displayed quote does not show what every alternative venue could have offered.
• Confusing an estimate with an actual fill: Pre-trade spread and impact estimates do not replace review of an executed order.