Risk disclosure

You can lose money trading on a betting exchange. Read this page in full before you trade live, and only ever stake money you can afford to lose.

1. Betting is gambling

Trading on the Betfair Exchange is gambling. Sporting events are unpredictable, prices move with the actions of other people, and no strategy — however systematic — removes the possibility of loss. Kelly Stake does not offer tips, predictions or any expectation of profit: it is tooling for strategies you supply.

2. Laying can cost far more than the stake

When you back a selection, the most you can lose is your stake. When you lay one, you take the other side of someone else’s bet, and your liability if it wins is your stake × (odds − 1). Laying £10 at odds of 8.0 risks £70. Kelly Stake shows liability, not stake, as the risk on a lay — check it before every trade.

3. Kelly sizing depends on your estimates being right

The Kelly criterion sizes a stake from the edge your model believes it has. If the model overstates that edge — as even good models sometimes do — Kelly stakes too much, and drawdowns can be deep and fast. Fractional Kelly lowers stakes and smooths the swings, but it cannot correct a wrong estimate. Long losing runs are a normal part of Kelly staking, not a sign that something has broken.

4. Backtests and paper trading are not live results

Backtests replay a strategy over historical prices, and paper mode simulates fills against live ones. Neither is real execution: real orders can go unmatched, match at worse prices, or move the market themselves, and history does not repeat on schedule. A strategy can perform worse live than it did on paper. Past performance, simulated or real, is not a reliable indicator of future results. Figures and charts on this website are illustrative.

5. Limits reduce risk; they do not remove it

Kelly Stake checks every order against the limits you set before it reaches the exchange. Those checks cannot predict outcomes, and they cannot protect you from limits set too high, from a strategy that stops working, or from ordinary market volatility. You remain responsible for the limits you choose.

6. Technology can fail

Data delays, Betfair API outages, or a lost connection between Kelly Stake and Betfair can mean missed exits, stale prices, unmatched orders, or being unable to close a position when you want to. Kelly Stake is designed to stop trading rather than trade blind when conditions degrade, but that cannot guarantee against loss during an outage — particularly in fast-moving in-play markets.

7. Charges reduce returns

Betfair charges commission on net winnings in each market, and may apply other charges to your account. These are Betfair’s, are paid to Betfair, and are outside our control. A strategy that looks profitable before charges may not be after them.

8. Only stake what you can afford to lose

Start in paper mode, understand what your strategy is doing and why, and move to live trading only with money you could lose in full without it affecting your life. Never borrow to trade, and never raise your limits to win back losses.

Responsible gambling

Kelly Stake is built to make risk visible, not to encourage more of it. You must be 18 or over to use it. If gambling is costing more time or money than you intended, or is affecting your mood, sleep, work or relationships, free and confidential help is available — independent of Kelly Stake:

Warning signs to watch for:

• raising your limits after a losing run to win it back;
• trading to relieve stress, boredom or low mood;
• checking positions compulsively, or losing sleep over open trades;
• staking more than you budgeted, or borrowing to fund it.

Betfair offers deposit limits, time-outs and self-exclusion in your Betfair account settings. They apply whatever you do in Kelly Stake, and they are the strongest controls you have. If you have self-excluded, do not use Kelly Stake — and if you ask us to close your account for gambling-related reasons, we will.