The dreaded rule 4. Rule 4 dictates what happens in the event of a horse being withdrawn before the race starts. Non runners as they are called affect the odds for all the other horses in the race because it’s one less horse that can win. Rule 4 is also known as Tattersals Rule 4 or just R4 for short. To be precise it’s Tattersals Rule 4c. Anyway, this post described Rule 4 and compares it to reductions that are made by betting exchanges.

If a horse is withdrawn it effects the odds of all the other runners. A horse who has better chance of winning effects the odds of the other runners to a greater extent. So, the withdrawal of a favourite has a much bigger affect on the chances of the other runners than that of a rank outsider. Rule 4 reductions are published as pence in the pound (that’s the British pound for visitors outside the UK).

Why do some people think rule 4 is unfair?

An obvious argument is that if I [the betting public] place a bet and my horse wins, why should my winnings be reduced because another horse has been withdrawn, my horse might have won anyway [even if the withdrawn horse was still running].

[box type="note"]Wealth warning. Antepost bets are those that are made before the day of the event.  Some bookmakers will not refund the stake if the horse or selection is withdrawn in the run up to the event.  Be warned.  Now that's a serious reduction. [/box]

Some bookmakers will reduce winnings by up to 90p in the pound if a short priced favourite is withdrawn and others impose a limit of 75p in the pound. Bookmakers calculate deductions based on the odds of the horse at the time of withdrawal. A rule 4 deduction table and an example can be found at the end of the post.

Compare Rule 4 to reduction factors used by betting exchanges

Traditional bookmakers price horses using fraction odds, e.g. 1/9 for a short priced favourite, or 14/1 for a rank outsider. For working out a rule 4 reduction odds bands are used; 2/11 to 2/17, 1/4 to 1/5 (see the rule 4 table below), etc.

Betting exchange work slightly differently. Odds are set by the market. The best odds on an exchange might only be matched by a small amount of money, whereas lower odds can be matched much more heavily.  As you might expect due to the difference between a betting exchange and a normal bookmaker, betting exchanges do things differently.

Information about each horse in the race can be accessed by clicking on it’s name. Part of this information is the reduction factor that will be applied in the event of any of the other horses in the race being withdrawn.

How does a betting exchange apply rule 4

Rule 4 deductions are applied as a percentage on a betting exchange rather than taking pence from the pound. The percentage reduction is applied to total return on the win market. If a 14/1 outsider on Betfair goes ‘non runner’ a 5% reduction would be applied to the total return (stake and profit). The exact calculation for reduction factors on Betfair are somewhat sketchy, but, suffice to say they are ‘worked out’ in a similar way to how bookmakers calculate rule 4.
[twocol_one]Horse odds at time of withdrawal

1/9 or shorter
2/11 to 2/17
1/4 to 1/5
3/10 to 2/7
2/5 to 1/3
8/15 to 4/9
8/13 to 4/7
4/5 to 4/6
20/21 to 5/6
Evens to 6/5
5/4 to 6/4
13/8 to 7/4
15/8 to 9/4
5/2 to 3/1
10/3 to 4/1
9/2 to 11/2
6/1 to 9/1
10/1 to 14/1[/twocol_one] [twocol_one_last] Deduction from winnings

90p in £
85p in £
80p in £
75p in £
70p in £
65p in £
60p in £
55p in £
50p in £
45p in £
40p in £
35p in £
30p in £
25p in £
20p in £
15p in £
10p in £
5p in £[/twocol_one_last]

Say a odds on favourite is a non runner. At the time the horse’s odds are 1/9. A punter backs the second favourite and it wins. Using the table above that means the winnings are reduced by 90 pence in the pound. For example, a £10 stake returns £100 (£90 winnings and £10 stake).

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