Rule 4 calculator

What Rule 4 does, and why it exists

When a declared runner is withdrawn after the final declaration stage — most commonly a veterinary scratching on the morning of the race, or a horse who blows the start and is formally withdrawn — the shape of the market changes. Whatever price you took earlier was, in part, a reflection of the other runners' chances. Remove one of them, and particularly if that one was fancied, the remaining horses all become a little easier to find. Tattersalls Rule 4(c) is the industry's way of taking account of this retrospectively.

The deduction is applied to winnings only, not to stake, and it is quoted in pence per pound. A 25p Rule 4 means that every pound of your winnings is reduced by twenty-five pence — a £100 winning return becomes £75. Your stake is always returned in full on top. The severity of the deduction scales with the odds of the withdrawn horse at the time of withdrawal: a withdrawn 2/1 second-favourite will trigger a much harsher cut than a 20/1 outsider whose absence barely troubles the book.

Two things worth knowing. First, if multiple horses are withdrawn before the race goes off, the deductions accumulate — two 25p reductions mean a total of 50p in the pound off your winnings, not 25p. The calculator handles that. Second, Rule 4 does not apply to bets placed after the withdrawal, since the reformed market will already have absorbed the change. It is the timestamp on your slip that matters, not the timestamp on the withdrawal.

In practice, Rule 4 tends to feel worse than it is because it lands as a surprise at settlement. A £20 each-way on a 5/1 shot with a 30p Rule 4 is still a perfectly acceptable result; it is just a less handsome one than it would have been. Best to factor the possibility in, particularly when backing against a short-priced favourite who might not make the start.

Worked example

You have backed a winner at 4/1. Before the off, the 2/1 favourite is withdrawn at the start. The Tattersalls Rule 4 scale dictates that a withdrawal at 2/1 triggers a deduction of 30 pence in the pound of winnings. Your £10 winning stake would, without any deduction, pay £40 in winnings (plus the £10 stake back, total £50). The deduction of 30p in the pound takes 30% off the £40 of winnings — £12. Adjusted winnings are £28, total return £38. The stake is always returned in full; only the winnings are deducted.

Common mistakes

The deduction is on winnings, not on the total return, and not on the stake. The stake always comes back in full. The second error is to apply the deduction to your own price; the scale applies to the price of the withdrawn horse, not to the price you took. The third is to forget that multiple withdrawals are cumulative — two horses withdrawn at 6/4 and 9/2 would attract deductions of 35p and 10p per pound respectively, a combined 45p deduction. The total is capped at 90p in the pound, at which level the race is void and all bets are refunded.

What to watch for

Best Odds Guaranteed (BOG) rules interact with Rule 4 in ways that catch people out. If you took 4/1 at 8am and the starting price is 5/1 with a Rule 4 applied, your bet is settled at 4/1 minus the deduction, not at the SP. BOG only elevates you to SP if the SP itself is higher after the deduction has been applied to it. Ante-post bets typically stand regardless of subsequent withdrawals, so Rule 4 does not apply. In Irish racing, the equivalent rule (the Horse Racing Ireland withdrawal deduction) uses the same scale but phrases it slightly differently — the arithmetic is identical. The each-way calculator handles Rule 4 across both legs of an each-way bet in proportion.

Frequently asked questions

What is Rule 4?

Rule 4 is a bookmaker deduction applied to winnings when a horse is withdrawn from a race after betting has opened but before the off. It compensates the bookmaker for having priced up the market with that horse included. The full explainer walks through the history and rationale of the rule.

Does Rule 4 come off my stake or my winnings?

Only the winnings. The original stake is always returned in full. A 25p-in-the-pound Rule 4 deduction takes 25% off the winning part of the return, not off the whole return and not off the stake.

What if multiple horses are withdrawn?

Multiple Rule 4 deductions are additive. Two horses withdrawn at 6/4 and 9/2 would attract deductions of 35p and 10p respectively per pound of winnings, for a combined 45p deduction. The total is capped at 90p in the pound; at that point the race is declared void and all stakes are refunded.

Does Rule 4 apply to ante-post bets?

Generally no. Ante-post bets are taken on the understanding that all non-runners are treated as losing bets; in exchange, no Rule 4 deductions are applied if other horses are subsequently withdrawn. Check the individual bookmaker's ante-post terms — some firms offer non-runner no-bet on major festival races, which changes the calculation.