Rule 4 deduction
A Rule 4 deduction is a cut taken from the winnings of a horse racing bet when a runner is withdrawn after you struck your price, sized by the odds the withdrawn horse was trading at when it came out. It exists because a missing horse makes every remaining runner more likely to win, so a fixed price taken earlier becomes better than the race now deserves. Your stake is never touched; only the profit shrinks.
How the Rule 4 figure is worked out
The deduction comes from the Tattersalls Rule 4(c) scale, written as cent off every euro of winnings. A withdrawn horse at 1/9 or shorter costs you 90c in the euro, a 3/1 shot costs 25c, and anything from 10/1 to 14/1 costs 5c. Longer than 14/1, nothing is taken.
Take a €10 win bet at 4/1 with a non-runner withdrawn at 3/1, which implied roughly a 25% chance of winning. Your €40 profit loses 25c in each euro, leaving €30, and with the stake back you collect €40 instead of €50.
When several horses come out, their deductions are added together, but the combined total cannot pass 90c in the euro. Practice around the edges varies between bookmakers: some waive the 5c band entirely, and each one sets out in its own rules whether its early price or the board price at withdrawal decides the rate.
Where you meet it, and what it is not
You will usually see it on your settled bet slip as a reduced return, often with the non-runner named beside it. It applies to prices taken before the withdrawal; bets placed after the market is reformed carry no deduction, and starting price bets are generally settled on a market that already reflects the smaller field.
Readers often mix it up with a non-runner refund, and the two sit on opposite sides of the same event. If your own horse is withdrawn, your stake comes back in full, while Rule 4 is what happens to everyone who backed a horse that did run.
It is a settlement rule, not a fee.
