Horse Racing - Tattersalls Rule 4(c) Deduction Scale (Per Pound)
You may have heard about bookmakers applying a rule 4 deduction and wondered what it was. The rule was introduced to protect bookmakers who have formed a book prior to a race only for a horse to become a non-runner before the race starts which can happen for numerous reasons. If, for example, the favourite in a race was priced at 2/1 but was withdrawn because it unseated its' rider and ran loose before the start then this would have a dramatic effect on the chances and therefore the odds of the other horses in the race.
In situations like this bookmakers are allowed to make adjustments on the bets take prior to the horse being withdrawn. The amount of the deduction depends on the price of the withdrawn horse at the time of the withdrawal.
The deductions are given as pence in the pound. Your stake remains the same but the winnings are reduced as follows,
| Price | Deduction |
|---|---|
| 1/9 or less | 90p |
| 2/11 to 2/7 | 85p |
| 1/4 to 1/5 | 80p |
| 3/10 to 2/7 | 75p |
| 2/5 to 1/3 | 70p |
| 8/15 to 4/9 | 65p |
| 8/13 to 4/7 | 60p |
| 4/5 to 4/6 | 55p |
| 20/21 to 5/6 | 50p |
| 1/1 to 6/5 | 45p |
| 5/4 to 6/4 | 40p |
| 13/8 to 7/4 | 35p |
| 15/8 to 9/4 | 30p |
| 5/2 to 3/1 | 25p |
| 10/3 to 4/1 | 20p |
| 9/2 to 11/2 | 15p |
| 6/1 to 9/1 | 10p |
| 10/1 to 14/1 | 5p |
| If over 14/1 | NONE |
For example, if you bet £10 on a horse at odds of 8/1 but the favourite was withdrawn when it's price was 3/1 then there would be a 25p in the pound deduction. Therefore, instead of your winning bet returning £90 (£10 X 8 + £10 returned stake) the returns would be reduced by 25p for every pound staked. So the returns would be (£10 X (8 X (1 - 0.25)) + £10 returned stake) = £70.
The formula is (STAKE X (ODDS X (1 - DEDUCTION FACTOR))) + STAKE
Notes
Any bets made after the horse has been withdrawn and the market has been reformed are not subject to a rule 4 deduction.
Some bookmakers do not apply the 5p deduction if a withdrawn horse is priced over 9/1 no deduction is made.
The betting exchanges have a different way of working out deduction factors. See the appropriate exchange terms and conditions for full details.