Rule 4 is a deduction applied to your winnings when a horse is withdrawn from a race after the betting market has opened. It exists because the withdrawal of a competitor improves the chances of every remaining horse, making the original odds more generous than they should be.
The Rule 4 Deduction Scale
The size of the deduction depends on the odds of the withdrawn horse at the time of withdrawal:
| Odds of Withdrawn Horse | Deduction |
|---|---|
| 1/9 or shorter (1.11) | 90p |
| 2/9 to 1/5 (1.20-1.22) | 80p |
| 1/4 to 2/7 (1.25-1.29) | 75p |
| 1/3 to 1/2 (1.33-1.50) | 65p |
| 8/15 to 4/5 (1.53-1.80) | 55p |
| 5/6 to evens (1.83-2.00) | 45p |
| 11/10 to 6/4 (2.10-2.50) | 35p |
| 13/8 to 7/4 (2.63-2.75) | 30p |
| 2/1 to 9/4 (3.00-3.25) | 25p |
| 5/2 to 3/1 (3.50-4.00) | 20p |
| 10/3 to 4/1 (4.33-5.00) | 15p |
| 9/2 to 11/2 (5.50-6.50) | 10p |
| 6/1 to 14/1 (7.00-15.00) | 5p |
| Over 14/1 (15.00+) | No deduction |
Worked Example
You place a £20 bet on Horse A at 4.00 (3/1). Before the race, Horse B (priced at 2/1) is withdrawn, triggering a 25p Rule 4 deduction.
- Gross return: £20 × 4.00 = £80
- Profit portion: £80 - £20 = £60
- Deduction: £60 × 0.25 = £15
- Net return: £80 - £15 = £65
Your profit drops from £60 to £45 because of the Rule 4 deduction.
When Rule 4 Does Not Apply
- Ante-post bets — No Rule 4, but no refund for non-runners either.
- Bets placed after the withdrawal — You get the new market odds; no deduction needed.
- Long-priced withdrawals (over 14/1) — The impact on the remaining market is negligible, so no deduction is applied.
Rule 4 and Best Odds Guaranteed
If you took an early price and your bookmaker offers Best Odds Guaranteed (BOG), the BOG comparison uses the SP after Rule 4 has been applied. The process is: apply Rule 4 to your fixed price, compare to SP, and pay the higher of the two.
Protecting Yourself
The simplest protection against heavy Rule 4 deductions is to bet closer to the off time, when the market has stabilised and late withdrawals are less likely. Alternatively, use exchanges where withdrawn runners are removed from the market automatically and remaining prices adjust organically.