Rule 4 deductions apply to horse racing bets when one or more horses are withdrawn from the race after you have placed your bet. The logic behind Rule 4 deductions is that if a horse is withdrawn from the race, the horses which do run stand a better chance of winning as there is less competition. Therefore, a deduction is taken from the winnings should your horse win or place to reflect the effects of the withdrawn horse.
If Rule 4 deductions were not applied, it may be possible for customers to lock in a profit if a horse is withdrawn. For example, if there were three horses in a race with odds of 1/1, 3/1 and 10/1 and the horse with the lowest odds was withdrawn, a £1 bet on each of the remaining two horses (£2 total stake) would return £4 and £11, guaranteeing a profit.
Rule 4 Calculator
The Free Rule 4 Calculator shown below can be used when a Rule 4 deduction has been applied to calculate the new odds of a horse.
The calculator is simple to use and just needs the following details entered:
- The odds of your horse when you placed your bet (before the Rule 4 deduction).
- The number of runners in the race before any withdrawals
- The stake you placed on your horse
- If your bet was each way or not
- If the race is a handicap race
- The odds of each withdrawn horse at the time they were withdrawn. You can add multiple withdrawals by clicking on ‘Add Non Runner’.
- The deduction percentage which is an optional field.
How to calculate Rule 4 deductions
It can be a bit daunting if a Rule 4 deduction is applied as you may be unsure of your returns should your bet win. However, it’s relatively easy to calculate your new returns after a Rule 4 deduction.
Firstly, you can use the Free Rule 4 Calculator above but if you’d like to understand how to do it manually, we’ll show you below.
Be aware that Rule 4 deductions are applied to your winnings and not your total returns.
The table below shows the percentage of the deduction made to your winnings depending on the odds of the withdrawn horse.
Odds of non runner when bet placed
Rule 4 Deduction per £1
Rule 4 Deduction %
1/9 or shorter
1.11 or shorter
2/11 to 2/17
1.18 to 1.12
1/4 to 1/5
1.25 to 1.20
3/10 to 2/7
1.30 to 1.29
2/5 to 1/3
1.40 to 1.33
8/15 to 4/9
1.53 to 1.45
8/13 to 4/7
1.62 to 1.57
4/5 to 4/6
1.80 to 1.66
20/21 to 5/6
1.95 to 1.83
Evens to 6/5
2.00 to 2.20
5/4 to 6/4
2.25 to 2.50
8/5 to 7/4
2.60 to 2.75
9/5 to 9/4
2.80 to 3.25
12/5 to 3/1
3.40 to 4.00
16/5 to 4/1
4.20 to 5.00
9/2 to 11/2
5.50 to 6.50
6/1 to 9/1
7.00 to 10.00
10/1 to 14/1
11.00 to 15.00
How do Rule 4 deductions change the odds of your bet?
When matched betting, it can be useful to know the new back odds for your horse after a Rule 4 deduction has been applied. Thankfully, this is relatively easy to determine using the simple formula below. You may wish to know the new back odds should you have not yet placed your lay bet and need to calculate the ideal lay stake to use based on the new back odds.
New back odds after a Rule 4 deduction = (odds you took – 1) x (1 – Rule 4 deduction in £) + 1
Therefore, if you placed a bet on a horse at odds of 4.0 and the Rule 4 deduction was £0.65, the new odds on your horse would be:
(4 – 1) x 1 – (0.65) + 1 = 2.05
What to do if you placed your lay bet before a Rule 4 deduction
As your returns will be less from the bookmaker if your horse wins after a Rule 4 deduction, you may think that you could lose money if that happens as your lay bet was to cover a greater amount. However, betting exchanges apply Rule 4 deductions as well and so there won’t be a great deal of difference in your qualifying loss. However, if you are using a free bet with the bookmaker and a Rule 4 deduction is applied, you may make a smaller profit. This is because you generally make the biggest profit when using free bets at higher odds. As Rule 4 deductions reduce the odds of your bet, your overall profit may also be reduced.
Whether your bet is a qualifying bet or a free bet, you shouldn’t need to make any changes to your back or lay bets when a Rule 4 deduction is applied.