Crossing A Position Internally

If a broker's client A wants to sell 10,000 shares of a stock at the same moment client B wants to buy 10,000 shares of the same stock, the broker doesn't have to route both orders to an exchange and pay two sets of exchange fees — it can match them directly, internally, at a price derived from the current market. This is called crossing, or internalization, and it's a routine, heavily used part of how brokers and internal trading desks execute flow cheaply.

The core requirement is that the crossed price must be fair relative to the prevailing market — typically at or better than the National Best Bid and Offer at the moment of the cross — so that neither client is disadvantaged relative to what they'd have gotten by trading on an exchange. Both regulators and clients care about this because internalizing an order removes it from public price discovery: if a large share of order flow is crossed off-exchange, the publicly displayed market reflects a smaller fraction of true supply and demand, a concern regulators refer to as fragmentation of price discovery.

Crossing is also central to how internal crossing networks and some dark pools operate: rather than matching one specific buyer to one specific seller in real time, they pool many clients' orders and periodically match compatible buys and sells at a reference price, capturing the same cost savings at larger scale.