Horse Racing Rule 4

What is Rule 4?

Horse(s) Withdrawn For The Race

Sometimes, in a horse race, horses can be withdrawn before the race starts.

When a horse is withdrawn, any bets placed on the horse will be voided and refunded.

Because a horse is withdrawn, the remaining horses will have a higher probability to win. Therefore, to reflect the new probabilities, bookies will apply what we call "Rule 4".

Rule 4 Reduces The Odds Of The Remaining Horses

Rule 4 will reduce the odds of all horses by a certain percentage, even if you had placed a bet before the withdraw happens.

This reduction percentage is determined by the odds of the horse being withdrawn. The lower the odds of the horse being withdrawn, the bigger the reduction percentage.

Why Are They Allowed To Reduce The Odds? Surely This Isn't Legal?

Okay, lets look at an example, infact, an extreme example. Lets say there's a 3 horse race, and lets pretend that only one horse really has a chance and is a MASSIVE favourite at odds of 1.05 and the other two horses are 25.0 and 26.0 respectively.

So you bet £10 on the horse that is 25.0 to win the race. Just before the off, news comes in that the favourite can no longer race! Oh no! Now it's just a two horse race. But clearly you can't get paid out at 25.0 if your horse wins, as that would be massively unfair on the bookmakers. You could literally bet £10 on the 25.0 one and £10 on the 26.0 one and guaranteed over £200 profit. For this reason, the bookmakers are allowed to apply rule 4 otherwise they would be giving away humongous value.

What To Do If Your Odds Are Reduced?

If you had placed a bet on a race that has a horse withdrawn, don’t worry!


Exchanges will have the same Rule 4 applied on the race as well, which will reduce the odds of the horse you layed.

Both exchanges and the bookies will normally reduce the odds of the horses by a similar amount, so your bet will still be risk-free.

You don’t have to do anything; the exchange will automatically reduce the odds of your horse.


In the screenshot above, you can see that I:

  • layed Good Luck Charm at odds of 8.0
  • but after rule 4, the odds of Good Luck Charm are now 7.112 (reduction of 11.1%).

Similarly, the bookie will have the odds of Good Luck Charm reduced by a similar percentage.

However, if you took a certain qualifying loss while placing the bet, the qualifying loss may not be the same after Rule 4.

Sometimes, instead of taking a small 30p loss, you may now take 60p loss after Rule 4. However, the changes will often be small, and sometimes you may even get a small profit out of Rule 4, too.

So, if you had placed a bet on a race that had a horse withdrawn, you don’t have to do anything, and the changes in qualifying losses will be minimal.

Checking Actual Payout After Rule 4

After Rule 4 is applied, you can see the reduced odds of your horse on your bet history on your bookie and exchange.


rule 4 bookmaker

As the above screenshot shows, I placed a bet on Rufus King at odds of 3.75. After Rule 4 is applied, the odds of Rufus King had dropped to 3.06, shown by the bookie. “Rule 4 applied” is also shown. Your payout will also be based on the reduced odds, not the odds you took when placing the bet, even if your bet was placed before a horse has withdrawn.


rule 4 exchange

On Smarkets, I had layed Rufus King at 3.65, which after Rule 4, became 3.02.

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