What Does 4 Rule Deduction Mean In Horse Racing 

 May 29, 2023

By  Philip Borrowman

In this post, I will outline everything you need to know about the “Rule 4” of horse racing.

I have also created a calculator you can use to figure out what your adjusted payout will be.

Rule 4 Explained

Rule 4 is a key regulation in horse racing betting, designed to protect bettors and bookmakers from changes after bets have been placed.

This rule is applied when a horse is withdrawn from a race after bets have been accepted and the market hasn't had time to adjust to the change naturally.

In essence, when a horse is withdrawn, the chances of the remaining horses winning increase since there is now one less competitor.

If no adjustments were made, bettors who bet early could take advantage of higher odds that no longer reflect the probability of their chosen horse winning.

Rule 4 provides a mechanism to adjust the payout odds in the event of a late horse withdrawal.

The scale of the deduction is based on the odds of the withdrawn horse at the time of withdrawal.

The shorter the odds of the withdrawn horse, the larger the deduction, as its withdrawal has a greater impact on the remaining field.

Here's an example of such a table. Please note, this is a general guideline, as specific deductions may vary.

Odds when withdrawn (fractional)

Decimal equivalent

Scale of deduction (per £)

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
Over 14/1

1.11 or lower
1.18 to 1.12
1.25 to 1.20
1.30 to 1.29
1.40 to 1.33
1.53 to 1.44
1.62 to 1.57
1.80 to 1.67
1.95 to 1.83
2.00 to 2.20
2.25 to 2.50
2.63 to 2.75
2.88 to 3.25
3.50 to 4.00
4.33 to 5.00
5.50 to 6.50
7.00 to 10.00
11.00 to 15.00
Over 15.00

No deduction

As a reminder, these values can change and might be different based on the bookmaker.

Always check the official rules for the specific event or with your bookmaker. If you feel you have been short-changed by a bookmaker, you can contact the British Horseracing Authority to make a complaint.

As you can see from this post about Ladbrokes not adequately implementing the rules, so this calculator below and odds table above will help you know exactly how much you are due to be paid out when a rule 4 deduction takes place.

Rule 4 Deduction Calculator

Example Input:

Let's say you place a bet with a stake of £10 at odds of 5/1, and a horse is withdrawn resulting in a Rule 4 deduction of 30p. Here's how you would input this:

Stake Amount (£): 10

Odds: 5/1

Deduction (pence per £): 30

Stake Amount (£):


Deduction (pence per £):

Here is an example bet affected by the 4 rule:

Let's say you've placed a £10 bet on a horse at odds of 5/1 (6.00 decimal), which translates to a potential return of £60 (£50 profit plus your £10 stake).

Before the race starts, another horse with odds of 2/1 is withdrawn.

According to the Rule 4 deductions table, a horse withdrawn at odds of 2/1 translates to a 30p per £1 deduction.

Here's the math explained:

  • Identify the profit from your bet: £50
  • Calculate the Rule 4 deduction: £50 * 0.30 (for 30p per £1) = £15
  • Subtract the deduction from your original potential profit: £50 - £15 = £35
  • Add your stake back in for your total return: £35 + £10 = £45

Therefore, your revised return, if your horse wins, is £45 instead of £60 due to the Rule 4 deduction.

Here is how it looks in table form:

Original Stake

Original Odds

Potential Return

Withdrawn Horse's Odds

Rule 4 Deduction

Revised Profit

Revised Return





30p per £1



Remember, Rule 4 is designed to reflect the increased chance of your horse winning after another horse is withdrawn.

It's a measure to ensure fair betting for all participants.

Does the 4 rule apply to all race events?

Yes, Rule 4 is a fundamental part of the horse racing betting system in the UK.

It's implemented by bookmakers to adjust the odds and payouts in the event of a horse being withdrawn from the race after bets have already been placed.

However, there are certain conditions under which Rule 4 does not apply even in the UK.

For instance, if a horse is withdrawn before the day of the race - specifically, before the "final declaration" stage (which is usually around 48 hours before a flat race and 24 hours before a jumps race) - Rule 4 will not be invoked because the market will have sufficient time to adjust naturally to this non-runner.

So, while it's a widely used principle in the UK horse racing market, there are still exceptions and it's always best to check the specific rules and terms with the bookmaker you are betting with.

Does Rule 4 Affect Accumulator Bets?

Yes, accumulator bets are affected, but it does so in a slightly different way than it affects single bets.

An accumulator is a bet that combines multiple selections into one wager. For the bet to win, all selections must be successful.

If a horse in an accumulator bet is withdrawn after you've placed your bet, it is treated as a non-runner.

This means that this part of the bet is void, and the accumulator adjusts down by one selection.

For example, a treble (an accumulator with three selections) would become a double, a double would become a single, and a single would be void.

If a Rule 4 deduction is applied due to a withdrawn horse, the deduction applies only to the winnings from the part of the accumulator that included the race from which the horse was withdrawn.

The rest of the accumulator is unaffected by the Rule 4 deduction.

Let's take an example. Suppose you have a treble bet with a £10 stake, and the odds for the three horses are 2/1, 3/1, and 4/1. If the 4/1 horse is withdrawn, your treble becomes a double.

If a Rule 4 deduction is applied to the 4/1 race, it doesn't affect your return from the other two races. The 4/1 part of the bet is treated as void.

Do Each-Way Places Change with Rule 4?

It does not generally affect the terms of each-way betting, such as the number of places paid out or the fraction of the odds at which these places pay.

However, if enough horses are withdrawn from a race, it can potentially affect the each-way terms.

The number of places that pay out in a race often depends on the number of runners. If withdrawals reduce the field below certain thresholds (for example, below 16 runners for a typical handicap race), the number of places paid may be reduced.

So, while Rule 4 itself doesn't change each-way terms, the same event (a horse being withdrawn) can lead to both a Rule 4 deduction and a change in each-way terms.

As always, the exact rules can vary by bookmaker and jurisdiction, so it's recommended to check the specific rules where you place your bets.

Are There Any Exceptions To Rule 4?

Yes, there are a few notable exceptions to Rule 4 in horse racing betting:

  • Timing of Withdrawal: Rule 4 deductions typically do not apply if a horse is withdrawn before the "final declaration" stage, which is usually around 48 hours before a flat race and 24 hours before a jumps race in the UK. This is because the betting market is considered to have sufficient time to adjust naturally to this non-runner.
  • Odds of the Withdrawn Horse: If the odds of the withdrawn horse are greater than 14/1 at the time of withdrawal, no Rule 4 deduction is usually applied, as its impact on the rest of the field is considered minimal.
  • Betting Exchanges: On betting exchanges, deductions generally do not apply to matched bets. Unmatched bets might be cancelled or suspended when a horse is withdrawn, giving bettors the opportunity to reconsider their position given the new odds.

While Rule 4 might initially seem complex, once understood, it provides a fair method of adjusting payouts in response to late changes in the field of runners.

It's important to remember that not all betting platforms apply Rule 4 in the same way, particularly betting exchanges, and bettors should familiarize themselves with the specific rules of the platform they're using.

Philip Borrowman

I am a full-time marketer and part-time Betfair trader. I have over 10 years of experience in the pre-race and in-play horse trading markets and spend my days writing guides, tips and tricks to help beginner Betfair traders find their way to a profitable second income. Read my story of trading on Betfair.

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