Definition of Rule 4 Deductions

What does the term "Rule 4" mean in the world of horse racing and sports betting? What is the definition of the term "Rule 4 deduction?"

Let's say that you are betting on a horse race and decide to back "Lucky Strike" at 4/1 to win.

"Lucky Strike" has the second best odds to win the race, behind "Midnight Blue", who is a staggering 1/6 to win. "Midnight Blue" has won every race that he has entered as of late and is practically unbeatable.

"Midnight Blue" injures himself before the race and is forced to pull out. Suddenly your 4/1 wager on "Lucky Strike" is looking much better, as the favourite to win is out of the race! Tough luck for the sportsbook, right?

Wrong.

There is where "Rule 4" comes in.

"Rule 4" deductions are made by a sportsbook whenever a horse is forced to pull out of a race.

"Rule 4" is a formula that is applied to all of the payouts on the remaining horses in the race. The better the horse is that pulls out, the more of a negative impact there will be on your earnings.

Under the "Rule 4" formula, you would lose 85% of your winnings if "Midnight Blue" pulled out of the race, as there were the favourites to win. So, your £300 pounds in potential winnings would be cut back drastically to just £45.

This represents 15% of the original winnings, based on the "Rule 4" formula.

If an underdog is forced to pull out of a race, the resulting "Rule 4" impact will be much more minimal, as the quality of the field won't drop that much.

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To understand the impact to your potential winnings of a horse pulling out of a race, please consult the table below:

Price of Non-Runner When Bet Was Placed (Fractional), Decimal Odds, Rule 4 Deduction (%)

1/9 or less, 1.11 or less, 90%
2/17 to 2/11, 1.12 to 1.18, 85%
1/5 to 1/4, 1.2 to 1.25, 80%
2/7 to 3/10, 1.29 to 1.30, 75%
1/3 to 2/5, 1.33 to 1.40, 70%
4/9 to 8/15, 1.45 to 1.53, 65%
4/7 to 8/13, 1.57 to 1.62, 60%
4/6 to 4/5, 1.66 to 1.80, 55%
5/6 to 20/21, 1.83 to 1.95, 50%
Even to 6/5, 2.00 to 2.20, 45%
5/4 to 6/4, 2.25 to 2.50, 40%
8/5 to 7/4, 2.60 to 2.75, 35%
9/5 to 9/4, 2.80 to 3.25, 30%
12/5 to 3/1, 3.40 to 4.00, 25%
16/5 to 4/1, 4.20 to 5.00, 20%
9/2 to 11/2, 5.50 to 6.50, 15%
6/1 to 9/1, 7.00 to 10.00, 10%
10/1 to 14/1, 11.00 to 15.00, 5%
Over 14/1, Over 15.00, No Deduction