The terms come from brokerage. An A-book broker passes your orders to the market; a B-book broker takes the other side itself. Prop firms use the same words for a related question: is your funded account trading real money in a real market, or is it a simulation the firm pays out on?

The three models

The three models. B-book (simulated): Stay in a simulation: The firm’s revenue, mostly fees: The firm runs short of cash if payouts outgrow sales; A-book (real capital): Go to a real market: Real trading profit, shared: Fewer firms; strict selection; Hybrid: Simulated for most; real for proven traders: Both: Depends on how many traders are moved to real capital
The three models: the figures from this section at a glance.
ModelYour tradesWhere payouts come fromMain risk to you
B-book (simulated)Stay in a simulationThe firm’s revenue, mostly feesThe firm runs short of cash if payouts outgrow sales
A-book (real capital)Go to a real marketReal trading profit, sharedFewer firms; strict selection
HybridSimulated for most; real for proven tradersBothDepends on how many traders are moved to real capital

Most retail forex prop firms are B-book: FTMO, for example, says its accounts use fictitious funds. Topstep is closer to a hybrid: its Combine and Express Funded Accounts are simulated, and a small share of traders, 0.71 per cent of Express Funded traders in 2025, are called up to a Live Funded Account trading Topstep’s capital.

Why it affects your payout

In a B-book firm, every payout is a cost to the firm, paid from fees. The firm stays healthy as long as fee income comfortably exceeds payouts. That gives B-book firms a reason to keep rules strict and to scrutinise payouts closely, and it is why a sudden run of winning traders, or a drop in new sign-ups, can push a weak firm into delaying or stopping payouts.

A firm that routes proven traders to real capital earns when they earn. That aligns its interest with yours, but it can afford to do it for only a few traders, which is why real-capital programmes are selective.

What to look for

  • A long, dated record of payouts: the best evidence a B-book firm’s finances work.
  • Clear disclosure of whether accounts are simulated. Established firms state it.
  • A route to real capital, if offered, with published criteria.
  • Stable payout rules. Firms under financial strain tend to tighten rules first.

Neither model is a scam in itself. A simulated model that is disclosed and pays reliably is the industry norm; what matters is whether the firm can keep paying. See how to check a firm actually pays.

Frequently asked

What is a B-book prop firm?

A firm whose funded accounts are simulations, paying traders a share of simulated profit from its own revenue, mostly challenge fees. Most retail forex prop firms work this way; FTMO says its accounts are demo accounts with fictitious funds.

What is an A-book prop firm?

A firm that puts traders' orders into real markets with its own capital and shares the real profit. Few retail firms do this for most traders; some, such as Topstep with its Live Funded Account, move a small share of proven traders to real capital.

Is a B-book prop firm a scam?

Not in itself. It is the industry's standard model and is legal when disclosed. The risk is financial: payouts depend on the firm's revenue, so check its payout record and stability.

How can I tell which model a firm uses?

Read its terms and risk disclosures: established firms say whether accounts are simulated. Look for any published route to a live account and its criteria.