What is Rule 4?

Rule 4 is a general, industry-wide betting rule, which governs the scale of deductions to winning bets in the event that one or more horses are withdrawn from a race. Logically, if a horse is withdrawn, the probability of any of the remaining runners winning increases, so Rule 4 effectively adjusts the odds of each horse accordingly. It is worth noting that Rule 4 only applies after the final declaration stage, 24 or 48 hours before the race, and is applied based on the price of the withdrawn horse at the time of its official withdrawal, according, the British Horseracing Authority (BHA).

Obviously, the likelihood of any horse winning is (nominally) reflected by the odds offered by bookmakers at any given time, so Rule 4 deductions – which are usually expressed as pence in the pound, or as a percentage – are applied on a sliding scale, inversely proportional to those odds. At one end of that scale, horses trading at odds of 1/9 or shorter at the time of withdrawal result in a deduction of 90p per £1. At the other, horses trading between 10/1 and 14/1, inclusive, at the time of

withdrawal result in a deduction of 5p per £1. Beyond that price range, Rule 4 does not apply to any withdrawn horse. Of course, it is possible that two or more horses may be withdrawn from a race, in which case cumulative Rule 4 deductions may apply. However, the total deduction will never be more than 90p per £1.