A dead heat is when two or more runners finish tied for the same place.
In order to calculate your returns in the event of a dead heat, you would need to divide your total stake by the number of selections which finished tied.
The bet is then paid out at full odds, to the divided stake.
For example: a £10 win bet on a horse at 10/1 would return a total of £110.
However, if the same £10 bet had two horses tied for first place, this will divide your stake by two, making it a £5 bet at 10/1 and would return a total of £55 with the remaining £5 stake being lost.