Can I cancel a bet after I place it?
You can cancel a placed bet only by using Withdraw Bet. Withdraw Bet returns your stake immediately if every selection is pre-event and the odds are unchanged since you placed the bet. For the full conditions, see "How does Withdraw Bet work?"
A placed bet can never be modified. Once you click Bet now and a registration number is issued, you cannot change the selections, the stake, or the odds. If you need a different bet, withdraw the original (if possible) and place a new one.
What can I do if I placed a bet by mistake and can't withdraw it?
If Withdraw Bet is not available on your bet, the bet cannot be cancelled. This happens when the odds have changed since you placed the bet, or when the event has gone live. The rules that apply are set out in Betting Rules, paragraph 1.2.
Check whether Cash Out is offered for your bet. Cash Out lets you settle the bet at a value based on the current odds. Cash Out is an extra service, and its value is not guaranteed. If it is missing from your bet, see "Why isn't Cash Out available on my bet?"