Rule 4 (officially Tattersalls Rule 4(c)) is a standard provision in horse racing betting that allows bookmakers to reduce winnings when one or more horses are withdrawn from a race after the betting market has been set. Because the remaining runners now face less competition, their effective win probability increases — Rule 4 adjusts winnings to reflect this.
The deduction scale is set according to the odds of the withdrawn horse. The shorter the price of the non-runner (meaning it was a strong favourite), the larger the deduction applied. A withdrawn 1/5 shot (a near-certain favourite) triggers a 75p in the £ deduction, as the remaining field benefited enormously from its absence. A withdrawn 14/1 outsider triggers only a 5p in the £ deduction.
Standard deduction table (approximate):
- Odds shorter than 3/10: 75p in £
- 2/5 to 1/3: 70p in £
- 4/9 to 8/15: 65p in £
- 8/13 to 4/6: 55p in £
- 4/5 to Evens: 35p in £
- 11/8 to 7/4: 25p in £
- 15/8 to 5/2: 20p in £
- 11/4 to 4/1: 15p in £
- 9/2 to 11/2: 10p in £
- 6/1 to 9/1: 5p in £
- 10/1 and beyond: no deduction
Bet timing matters: Rule 4 applies only to bets placed before the non-runner was declared. If you bet on the exchange or at a bookmaker after the withdrawal is announced, you take the revised odds and no deduction applies.
Example
You back a horse at 5/1. Before the race, the 4/6 favourite is withdrawn. A 4/6 favourite triggers a 55p in the £ deduction. Your winnings are reduced by 55%: a £10 bet at 5/1 normally returns £60 (£50 profit + £10 stake). After Rule 4: profit is reduced by 55% to £22.50, so your total return is £32.50 instead of £60.