Operations
What Is a B-Book Prop Firm? A-Book, B-Book and Hybrid
What B-book means at a prop firm, how A-book and hybrid models differ, what each costs, and how to describe your model honestly on your site.
- By PipValley Editorial
- Published
- 4 min read
The terms come from retail brokerage, where a B-book broker takes the other side of client trades and an A-book broker passes them to the market. In a prop firm the trader has no deposit at risk beyond the fee, so the economics differ, but the risk principle is the same: on the B-book, the firm carries the outcome of the trader's results.
How do the three models compare?
| Model | What happens to trades | Firm's exposure | Extra cost |
|---|---|---|---|
| B-book | Stay in the simulated environment | Payouts, funded from fees | None beyond the platform |
| A-book | Copied to a live account at a broker or LP | Live P&L offsets payouts | Spreads, commissions, bridge, broker contract |
| Hybrid | Most stay internal; selected traders copied live | Mixed | Routing rules, bridge, reporting |
Why would a firm A-book anyone?
To pay its best traders more sustainably. A trader who passes a large evaluation can withdraw many times the fee they paid; if their positions are mirrored live, their profits partly fund their own payouts. Firms rarely A-book everyone, because live execution costs money and only makes sense for traders with consistent records.
Hybrid setups need tooling: a bridge between platform and liquidity provider, a risk engine that tags accounts for routing, and reporting that separates simulated payouts from live P&L. It is an operations choice to make once you have payout data, not a launch requirement.
What should you say publicly?
You don't need to discuss your book model on the website. You must not imply live market execution or real capital you do not provide. If you do A-book and want to talk about it, describe it accurately: what is mirrored, when, and that the trader's own account remains simulated unless you state otherwise.
Topstep is one of the few firms to publish a live share: it reports that 0.71% of participants in its Express Funded Account were called up to a Live Funded Account in 2025, as stated by the firm.
Questions
Are all prop firms B-book?
Nearly all evaluation firms keep evaluation trades simulated, which is B-book by nature. Some copy selected funded traders to live accounts, making them hybrid.
Is B-booking a scam?
No. It is how the evaluation model works: the firm sells a test and pays rewards from fees. It becomes a problem only when rules are hidden, changed after purchase or applied inconsistently at payout time.
Do I need a liquidity provider to start a prop firm?
Not to launch. Your platform needs a price feed, usually supplied by the vendor. A liquidity provider and bridge matter only if you decide to A-book traders later.
Sources
Illustrative figures, not a forecast. Nothing on this site is legal, tax or financial advice. PipValley is a web design studio; we don’t sell challenges, run trading accounts or provide trading platforms. Spotted something out of date? Tell us and we’ll fix it with the date.
Keep reading
Related guides.
Do Prop Firms Use Real Money? What Operators Actually Do
How Do Prop Firms Manage Risk? The Operator's Toolkit
Is a Prop Firm a Broker? The Difference That Matters
How Do Prop Firms Make Money? An Operator Explains
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