Liability vs stake on Polymarket, explained
When you type an amount into Desk, one setting decides what that number actually means — the Liability / Stake toggle. Get it right and your risk is exactly what you intended; get it wrong and a lay can cost more than you expected.
The two modes
The toggle changes the meaning of the figure you type on every trade:
- Liability — the number is your maximum risk: the most you can lose on that click, full stop. Desk works out the position size that fits that risk.
- Stake — the number is the backer's stake, the classic Betfair convention. On a back this is simply what you put in; on a lay, the liability can be larger than the stake.
On a straight back (buying "Yes") the two modes barely differ — your stake and your worst case are close. The gap only opens up on a lay, and that's where the toggle matters.
Why a lay's liability can exceed its stake
When you lay, you're taking the other side of a bet — effectively acting as the bookmaker. You win the backer's stake if the outcome doesn't happen, but you must pay out their winnings if it does. At longer odds, those winnings are a multiple of the stake.
Take a concrete case. You lay at 4.0 decimal odds against a $10 backer's stake:
- If the outcome doesn't happen, you keep the $10 stake — that's your profit.
- If it does happen, you owe the backer their winnings: $10 × (4.0 − 1) = $30. That $30 is your liability.
So a $10 stake carries a $30 liability here — three times what you "typed" if you were thinking in stake terms. In Stake mode you'd enter 10 and risk 30; in Liability mode you'd enter 30 and risk exactly 30, with Desk sizing the underlying position to match.
The longer the odds you lay at, the bigger the multiplier. Lay at 10.0 and a $10 stake carries a $90 liability. If you size in Stake mode without doing that arithmetic, your real risk can be far larger than the number in the box.
Which mode should you use?
If you're new, use Liability. It's the safer mental model: the number you type is simply the most you can lose, on every trade, whichever side you take and whatever the odds. There's no multiplier to keep in your head — what you enter is what's at risk.
Stake mode suits traders who already think in Betfair terms and want the backer's stake to be the headline figure. It's a convention, not a safety feature — the liability is still there, it's just shown separately rather than being the thing you type.
Leave Desk in Liability mode while you're learning. Once you instinctively convert stake to liability at a glance, switch if the Betfair convention suits you better. You can change it any time in the sizing controls.
In short
Same trade, same underlying risk — the toggle only changes which number you type to get there. Liability makes your worst case the input; Stake makes the backer's stake the input and leaves the liability to be read off separately. When in doubt, type the amount you're willing to lose and keep it in Liability mode.