You ask for odds of 3.0 on a team. Nobody is offering that price yet, so your bet sits in a queue. Ten minutes later someone agrees, and the bet is matched. Nothing about the result has changed. What changed is that another person took the other side.
That queue is the heart of every betting exchange. This article walks through the mechanics: how prices form, how bets are matched, how liability is calculated, what happens in-play and at the start of an event, and how settlement and commission work.
The Order Book: Where Exchange Prices Come From
Each selection in an exchange market has two sides. On one side are backers, who want the selection to win. On the other are layers, who want it to lose. Every unmatched bet is an order waiting at a price. The exchange lists the best three or so prices on each side with the amount of money available at each.
The best back price on screen is really the best price a layer is offering. The best lay price is the best price a backer is asking for. The gap between them is the spread. In a busy market such as a Premier League match it is often a single tick. In a quiet market it can be wide.
How Bets Get Matched
When you place a bet at a price that someone on the other side is already offering, it is matched straight away. If you ask for a better price than anyone is offering, your bet waits as an unmatched order. Other customers can then take it.
Bets can be partly matched. If you want to back for £100 at 3.0 and only £60 is available, £60 is matched and £40 waits. Each matched part is a contract between you and one or more other customers, and the exchange holds both sides’ money until settlement.
The minimum stake on Betfair Exchange in the UK is £1, down from £2 in February 2022.
Back and Lay Maths
Exchanges quote decimal odds, which include the stake. Backing £10 at 4.0 returns £40 if it wins: £30 profit plus your £10 stake.
Laying is the mirror image. When you lay, you accept another customer’s stake and agree to pay their winnings if the selection wins. Your liability is that payout:
Liability = (odds − 1) × backer’s stake
| Lay price | Backer’s stake you accept | Your liability if it wins | Your profit if it loses |
|---|---|---|---|
| 2.0 | £10 | £10 | £10 |
| 4.0 | £10 | £30 | £10 |
| 9.0 | £10 | £80 | £10 |
The last row is Betfair’s own example: laying at 9.0 for a £10 stake puts £80 at risk to win £10. That is why laying long odds is where most beginners get hurt. Profits shown here are before commission.
Trading: Backing and Laying the Same Selection
Because you can back and lay, you can also trade. Back a team at 3.0, and if the price drops to 2.5 you can lay at the shorter price. If you size the lay stake correctly, the two bets offset and leave a small profit whichever way the match goes. For a £10 back at 3.0, that means laying about £12 at 2.5, which leaves roughly £2 either way before commission. If the price moves the other way, the same move locks in a loss. Exchanges net all your bets in one market together, which is what makes this work.
What Happens In-Play
Once an event is live, exchanges hold each new bet for a short delay before it is matched. This protects customers who have orders waiting from people watching a faster feed. On Betfair the delay is usually between 1 and 12 seconds depending on the sport, for example 5 seconds for basketball and 3 for darts. Since October 2025 Betfair has let passive bets, the ones that wait in the queue rather than match straight away, skip the delay on darts and NBA markets, as they already could on tennis, baseball and American football.
Unmatched Bets at the Off
Unmatched orders in a pre-match market don’t automatically carry on into the event. On Betfair you choose one of three options:
- Cancel (the default): the unmatched part is cancelled when the event starts.
- Keep: the order stays in the market in-play.
- Take SP: the unmatched part is matched at the Betfair Starting Price. This is available on desktop.
The Betfair Starting Price (BSP) is worked out at the off by balancing backers’ Starting Price stakes against layers’ Starting Price liabilities. Betfair says no margin is built in.
Settlement and Commission
When the result is confirmed, the exchange settles the market. Winners are paid from the money held from the losing side. Commission is then taken from each customer’s net winnings in that market, so if you backed and laid the same horse, only your overall profit is charged.
Rates vary by exchange and country. On Betfair, UK and Irish customers pay 2%, 5% or 8% depending on their rewards package, and Matchbook charges 2%. Our guide to Betfair commission fees has the full detail.
Liquidity and Market Makers
An exchange is only as good as the money waiting in it. Big events attract enough customers to keep prices tight. Smaller markets depend on market makers: traders, often automated, who post back and lay prices on both sides and earn the spread. This is also why exchanges merge. Matchbook’s takeover of Betdaq in 2026 was framed around combining the two liquidity pools.
FAQ About How Betting Exchanges Work
Why is my bet unmatched?
Because nobody has offered the other side at your price yet. You can wait, change your price to the best available, or cancel the order.
How do you calculate lay liability?
Multiply the backer’s stake by the odds minus one. Laying £20 at 5.0 gives a liability of £80.
Why is there a delay on in-play bets?
To stop customers with faster pictures picking off orders that are waiting in the market. The delay varies by sport.
Can an exchange cancel a matched bet?
Only in limited cases set out in its rules, such as obvious errors or bets placed after an event that should have suspended the market. Check the exchange’s rules for each market type.
Every exchange runs on the same loop: orders wait, orders match, the market settles and commission comes off net winnings. Once that clicks, the rest is practice. Our step-by-step beginner guide shows how to place your first bets, and back vs lay strategy looks at when each side makes sense.
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