What is liability in lay betting?

The amount you pay if the outcome you laid happens: lay stake × (lay odds − 1). The exchange reserves it from your balance while the bet is open.

How do I calculate a lay stake?

For a cash bet, back stake × back odds ÷ (lay odds − commission). For a bonus bet, bonus × (back odds − 1) ÷ (lay odds − commission). Use decimal odds.

Can you lay bets in the US?

Not on a UK-style exchange, but buying No on a CFTC-regulated prediction market is the same position: it pays if the outcome doesn't happen.

Exchanges

Lay betting explained: liability, commission and the lay stake

A lay bet wins if the outcome doesn't happen. You risk the backer's winnings (your liability) to win their stake, less commission. US bettors get the same position by buying No on a prediction market.

Updated September 27, 2026 · TrueEdge Academy

Laying a bet means taking the bookmaker's side: you bet that an outcome will not happen. If you lay $100 at odds of 3.00, you win the backer's $100 stake when the outcome fails, and you pay out their $200 of winnings when it succeeds — that $200 is your liability. Exchanges charge commission on what you win. Laying is what makes UK-style matched betting work, and in the US the same position comes from buying No on a prediction market.

Laying $100 at 3.00 (+200)

Lay stake (the backer's stake you accept): $100
Liability: $100 × (3.00 − 1): $200
Outcome doesn't happen: you win: +$100, less commission
With 2% commission: +$98
Outcome happens: you pay: −$200

Illustration. Liability is what the exchange holds from your balance while the bet is open, so you need $200 available to place a $100 lay at 3.00.

Liability grows fast with the odds

Liability is lay stake × (lay odds − 1). At 1.50 a $100 lay risks $50; at 11.00 the same lay risks $1,000. That is why laying long shots ties up a lot of money for a small win, and why the arithmetic of matched betting pushes you toward short lay odds when you have the choice.

The lay stake formula for matched betting

In matched betting you back an outcome at a sportsbook and lay the same outcome on an exchange, sized so the result is the same either way. For a cash (qualifying) bet the lay stake is the back stake × back odds ÷ (lay odds − commission). For a bonus bet, where the stake is not returned, replace back stake × back odds with the bonus's winnings: bonus × (back odds − 1). All odds here are decimal; how to read betting odds covers the conversion from American.

Worked: qualifying bet, $100 back at 3.00, lay at 3.10, 2% commission

Lay stake: 100 × 3.00 ÷ (3.10 − 0.02): $97.40
Liability: 97.40 × 2.10: $204.55
Back wins: +$200 − $204.55: −$4.55
Lay wins: −$100 + ($97.40 × 0.98): −$4.55

Illustration. A small, known loss that unlocks a promotion is the whole point of a qualifying bet.

Worked: $100 bonus bet backed at 4.00, lay at 4.20, 2% commission

Lay stake: 100 × 3.00 ÷ (4.20 − 0.02): $71.77
Liability: 71.77 × 3.20: $229.67
Back wins: +$300 − $229.67: +$70.33
Lay wins: $71.77 × 0.98: +$70.33

Illustration. A 70% conversion — the same result converting a bonus bet gets by hedging at a second book.

Where US bettors can lay

The UK exchanges matched-betting guides assume, Betfair above all, aren't open to most US bettors. What US bettors have instead are CFTC-regulated markets — Kalshi, Polymarket US, Novig and ProphetX among them — where every market has a No side. Buying No on Team A pays $1 per contract if A does not win, which is exactly a lay of A. A lay at decimal odds L is the same position as buying No at 1 − 1 ÷ L: laying at 3.10 is buying No at about 67.7¢. Otherwise, US matched bettors hedge by backing the opposite outcome at another sportsbook, the method in matched betting in the US.

Worked: the qualifying bet again, laid by buying No at 68¢

Contracts needed (to match the $300 sportsbook payout): 300
Kalshi taker fee per contract: 0.07 × 0.68 × 0.32: 1.52¢
Cost: 300 × (68¢ + 1.52¢): $208.57
Team A wins: +$200 − $208.57: −$8.57
Team A doesn't: −$100 + $300 − $208.57: −$8.57

Illustration at a 1× fee multiplier. The contract count is back stake × back odds for a cash bet, and bonus × (back odds − 1) for a bonus bet. The venue's fee is what costs more here than the 2% commission in the exchange example.

Doing the sizing in TrueEdge

The Bonus Bet Converter on the calculators screen sizes the hedge for a bonus bet from the two decimal prices you type, and has a commission field that applies an exchange's commission as 1 + (d − 1)(1 − c). Set it to 0 for a sportsbook hedge. The calculators walkthrough works a conversion through both outcomes.

Frequently asked questions

What is liability in lay betting?: The amount you pay if the outcome you laid happens: lay stake × (lay odds − 1). The exchange reserves it from your balance while the bet is open.
How do I calculate a lay stake?: For a cash bet, back stake × back odds ÷ (lay odds − commission). For a bonus bet, bonus × (back odds − 1) ÷ (lay odds − commission). Use decimal odds.
Can you lay bets in the US?: Not on a UK-style exchange, but buying No on a CFTC-regulated prediction market is the same position: it pays if the outcome doesn't happen.