Internalisation: how brokers net client orders.

Picture two clients of the same broker pressing their buttons in the same second. One buys 2 lots of EUR/USD and the other sells 2 lots.

The broker does not need the wider market for either trade, because the two orders cancel each other out inside its own books. That is internalisation: a broker offsetting client orders against each other in-house, then dealing outside only for what is left over.

What does it mean to internalise an order?

In retail forex and CFD trading, your broker is usually the counterparty to your trade. When you buy, the broker sells to you. When another client sells, the broker buys from them.

Each trade is a separate contract between one client and the broker. The two clients never meet and never learn about each other.

Inside the broker, those contracts add up to one combined position per instrument. A client buy leaves the broker short and a client sell leaves it long, so opposite trades cancel. Adding them up this way is called netting.

Whatever survives netting is the net exposure, the amount on which the broker would gain or lose if the price moved.

The broker can then hedge that amount with a liquidity provider or keep some or all of it. The A-book and B-book lesson covers that choice.

Netting four orders: a worked example

Suppose four clients trade EUR/USD within a few seconds of each other. A standard lot is 100,000 euros, and every number here is illustrative.

Work through it one step at a time:

1. Add the buys: 3.0 + 1.0 = 4.0 lots, or 400,000 euros.
2. Add the sells: 2.0 + 0.5 = 2.5 lots, or 250,000 euros.
3. Match them: 2.5 lots of buying cancel 2.5 lots of selling, so 5.0 lots of client volume offset each other.
4. Find the rest: 4.0 minus 2.5 = 1.5 lots of client buying with nothing against it.
5. Clients are net long 1.5 lots, so the broker is net short 1.5 lots, or 150,000 euros.
6. A pip on one lot of EUR/USD is worth $10, so the broker's open risk is 1.5 × $10 = $15 per pip.

To remove that $15 per pip risk, the broker buys 1.5 lots from its liquidity provider, one outside trade in place of four.

Why the smaller hedge saves money

Every trade with a liquidity provider costs something: the provider's spread, a fee per lot, or both. Assume, purely for illustration, that each lot sent outside costs the broker $5.

Hedging every order on its own means 6.5 lots of outside trades: buy 4.0 and sell 2.5. At $5 a lot that is 6.5 × $5 = $32.50.

Hedging only the net means 1.5 lots, which costs 1.5 × $5 = $7.50. The broker ends with exactly the same position and saves $25.00 on this batch.

A broker with a steady stream of orders can repeat this all day, so the savings add up across thousands of trades.

How a matched pair earns the spread

Netting also explains how a broker can earn from client orders without taking a view on where the market goes.

Say the broker quotes EUR/USD at a bid of 1.10000 and an ask of 1.10010, a spread of 1.0 pip. In the same second, client E buys 2 lots at the ask and client F sells 2 lots at the bid.

1. The broker is short 2 lots to E at 1.10010.
2. The broker is long 2 lots from F at 1.10000.
3. The gap is 1.10010 minus 1.10000 = 0.00010, which is 1.0 pip.
4. On 2 lots, 200,000 euros × 0.00010 = $20.

Wherever the price goes next, the short to E and the long from F move by equal and opposite amounts. While both trades stay open, the broker's book is $20 ahead on the pair.

E and F still each have their own profit or loss. Their results depend on the price and their own costs, whatever the broker does with its book.

Where netting stops working

A match lasts only as long as both trades do. If E closes after an hour while F stays open, the broker is long 2 lots again with nobody on the other side, and it must hedge that exposure or carry it.

Timing opens a similar gap. Say the buy fills at the ask of 1.10010 and the matching sell arrives a minute later at a bid of 1.10030, after the price has risen.

For that minute the broker was short and unhedged. It sold to the buyer at 1.10010 and bought from the seller at 1.10030, so on 2 lots it lost 0.00020 × 200,000 = $40, where a same-second match would have earned $20.

One-sided flow is another limit. Around a big news release, clients can pile into the same direction, so there is little to net and the residual grows quickly.

A broker can handle this with internal limits, such as a maximum net position per instrument, above which the residual is hedged. Those settings are private and differ from firm to firm.

What a broker does with the residual it chooses to keep is the subject of the hybrid and C-book lesson.

What internalisation means for your trades

Your contract is the same whether your order is netted or hedged. You trade at the broker's quoted price, and the broker is your counterparty either way.

On the matched part of the book, the broker has no stake in which way the price moves, because the two sides cancel. A conflict of interest can appear on the residual, if the broker keeps that exposure and gains when clients lose.

Netting lowers the broker's outside costs. Whether any of that saving reaches you through tighter spreads is the broker's decision, and you cannot measure it from outside.

To learn how your broker handles client flow, read the documents it publishes, often called an order execution policy and a conflicts of interest policy. Look for words such as principal, internalise or net.

The hedging policy lesson explains how to read those documents and which answers to ask for when they are vague.