Back & Lay Betting
Understanding back and lay betting is the most important technical concept in matched betting. Once you get this, everything else falls into place.
What Is a Back Bet?
Backing to Win
A back bet is a standard bet — you bet that a selection WILL win. This is what you do at a bookmaker. If the selection wins, you get paid; if it loses, you lose your stake.
Laying Against
A lay bet is the opposite — you bet that a selection will NOT win. On an exchange, you become the "bookmaker" for another bettor, collecting their stake if they lose.
✅ Back Bet Example
Context: £10 on Team A to win at 2.50.
- If Team A wins: bookmaker pays £25 (£15 profit + £10 stake back)
- If Team A loses/draws: lose £10 stake
What Is a Lay Bet?
A lay bet is the opposite — you bet that a selection will NOT win (i.e. it will lose or draw). On a betting exchange, you become the "bookmaker" for another bettor. If the selection fails to win, you collect the backer's stake. If it wins, you pay the backer their winnings.
❌ Lay Bet Example
Context: Lay Team A to win at 2.55 on Betfair, £10 lay stake.
- If Team A does NOT win: you win £10 (the backer's stake)
- If Team A wins: you pay £10 × (2.55 – 1) = £15.50 — your lay liability
Lay Liability: The Critical Concept
When you place a lay bet, you must have the lay liability available in your exchange account. This is the amount you would lose if the selection wins.
Lay Liability = Lay Stake × (Lay Odds – 1)
High Odds = High Liability
Lay stake £20 at odds 3.00:
Liability = £20 × (3.00 – 1) = £40
Low Odds = Low Liability
Lay stake £20 at odds 1.50:
Liability = £20 × (1.50 – 1) = £10
Always check your lay liability before placing a lay bet to ensure you have sufficient funds in your exchange account. Our Matched Betting Calculator shows the full lay liability automatically.
How Back + Lay Creates a Matched Bet
When you back AND lay the same selection for the same effective amount, the two positions cancel each other out, leaving only the promotional value behind.
| Outcome | Back Bet (Bookmaker) | Lay Bet (Exchange) | Net P/L |
|---|---|---|---|
| Selection wins | +£15 profit | –£15.10 paid (minus small cross) | ≈ –£0.10 |
| Selection loses | –£10 stake | +£10 received from backer | ≈ £0 |
The small net difference (qualifying loss) comes from the back/lay odds gap and exchange commission. When a free bet is used instead of real money for the back bet, this small profit becomes real risk-free income — as there's no initial stake lost if the selection loses!
Why not just use a normal bookmaker?
Now that you've mastered the mechanics of back and lay betting, you might wonder why we don't just stick to tradition. Let's look at the core differences between a bookie and an exchange.
Next: Exchange vs Bookmaker →