Rule 4 Calculator: Step-by-Step Deduction Examples

Rule 4 deductions confuse many punters encountering them for the first time. Your winning bet pays less than expected, and the settlement slip shows a deduction you didn’t anticipate. Understanding the calculation removes this confusion and helps you assess non-runner risk before betting.

The principle is straightforward: when a horse withdraws after you’ve placed your bet, the remaining field becomes easier to beat. The deduction compensates for this reduced difficulty, ensuring you don’t receive full odds on a bet that’s become simpler to win. The scale of deduction depends on how likely the withdrawn horse was to win.

This guide walks through specific calculation examples—single non-runners, multiple non-runners, and each-way bets—so you can verify your own settlement calculations and understand exactly what to expect when Rule 4 applies.

The examples use realistic scenarios you might encounter on any raceday. Work through them once, and the mechanics become clear enough to apply to your own bets. The maths isn’t complicated—it’s just unfamiliar until you’ve done it a few times.

Single Non-Runner Example

The Rule 4 deduction scale links withdrawal odds to pence-per-pound deducted. The tighter the non-runner’s odds, the larger the deduction. No deduction applies if the withdrawn horse was priced above 14/1—the logic being that such a long shot wouldn’t have meaningfully affected the race’s difficulty.

Here’s the standard scale: odds of 1/9 or shorter trigger 90p deduction; 2/11 to 2/9 triggers 85p; 1/4 to 2/7 triggers 80p; and so on down to 14/1 and longer where no deduction applies. Each band represents a 5p step corresponding to implied probability ranges.

Consider a worked example. You’ve backed Horse A at 5/1 with a £10 stake. Before the race, Horse B withdraws at odds of 7/2. Consulting the scale, a 7/2 non-runner triggers a 30p deduction—meaning you receive 70p per £1 of your winnings.

Calculate the return: without deduction, £10 at 5/1 returns £60 (£50 profit plus £10 stake). With 30p Rule 4, your profit becomes £50 × 0.70 = £35. Add your £10 stake returned, and you receive £45 total instead of £60. The £15 difference reflects the reduced field difficulty after the 7/2 shot withdrew.

The deduction applies only to profit, not to stake. Your original stake always returns in full on a winning bet. This distinction matters for understanding exactly how much Rule 4 costs you: 30p in the pound on a 5/1 winner means 30% of your profit, not 30% of your total return.

Multiple Non-Runners Example

When multiple horses withdraw, their individual deductions combine. Back to our scenario: you’ve backed Horse A at 5/1 with £10. Two horses withdraw—Horse B at 7/2 (30p deduction) and Horse C at 5/1 (25p deduction). The combined deduction is 55p per £1.

Your profit calculation: £50 potential profit × 0.45 (retaining 45p after 55p deduction) = £22.50. Add your £10 stake, and you receive £32.50 instead of the £60 you’d have received with no withdrawals. Multiple non-runners can severely impact returns.

Crucially, combined deductions cannot exceed 90p in the pound. The maximum total Rule 4 deduction is 90p per £1, regardless of how many horses withdraw or how short their prices were. If three short-priced horses all withdraw with individual deductions of 40p, 35p, and 30p (totalling 105p), the actual deduction caps at 90p.

This cap protects punters from catastrophic deductions in unusual circumstances—though 90p in the pound still represents a severe reduction, leaving only 10% of your winnings after deduction. Races with multiple short-priced withdrawals can effectively eliminate most of your profit even with the cap in place.

The cap applies to the sum of all deductions, calculated after determining each individual deduction from the scale. Calculate each withdrawal’s deduction separately, add them together, then apply the 90p maximum if the total exceeds it.

Each-Way Rule 4 Example

Each-way bets apply Rule 4 to both win and place portions. If your horse wins, the deduction affects your win profit and your place profit. If your horse places without winning, the deduction affects only your place profit (since the win portion lost entirely).

Worked example: you back Horse A each-way at 10/1 with £10 each way (£20 total stake). Place terms are 1/4 odds, three places. Before the race, Horse B withdraws at 3/1, triggering a 35p deduction. Your horse wins.

Calculate the win portion: £10 at 10/1 = £100 profit. After 35p Rule 4: £100 × 0.65 = £65 profit. Add £10 stake returned = £75 win portion return.

Calculate the place portion: £10 at 10/4 (2.5/1) = £25 profit. After 35p Rule 4: £25 × 0.65 = £16.25 profit. Add £10 stake returned = £26.25 place portion return.

Total return: £75 + £26.25 = £101.25. Without Rule 4, you’d have received £110 (win) + £35 (place) = £145. The 35p deduction cost you £43.75 across both portions of your each-way bet.

If your horse had finished second instead of winning, only the place calculation would apply. You’d lose the £10 win stake, then receive £26.25 from the place portion. Rule 4 still deducts from that place profit.

Edge Cases and Disputes

Withdrawal timing affects which price determines the deduction. Bookmakers use the price at which the non-runner was trading when officially withdrawn, not necessarily the price at which you placed your bet. If odds moved significantly between your bet and the withdrawal, the deduction might differ from your expectation.

Late withdrawals—after betting has opened but before the race—trigger normal Rule 4 procedures. Very late withdrawals at the start may be handled differently by some bookmakers, particularly if they occur after the official “off” time. Checking specific terms clarifies how edge cases are treated.

Disputes about Rule 4 settlement typically concern which price applied at withdrawal time. Bookmakers maintain timestamped records of price movements, and independent services track market changes. If you believe a deduction was incorrectly calculated, request the specific withdrawal time and price used.

Industry SP bets handle Rule 4 differently from fixed-price bets because SP already reflects the final field. If you bet at SP and a horse withdraws before the off, your SP is calculated on the actual runners—no separate deduction applies because the starting price already incorporates the reduced field.

Accumulator Rule 4 applies per-leg with compounding effects. If one leg of a four-fold has a 30p Rule 4 deduction, that reduced profit rolls into subsequent legs. The impact compounds through the accumulator, sometimes significantly reducing final returns even when all selections win.

Rule 4 calculations follow mechanical rules that become predictable once understood. The deduction scale, the profit-only application, the 90p maximum cap, and the each-way treatment all operate consistently. Knowing these rules removes settlement surprises and helps you factor non-runner risk into betting decisions.

Consider Rule 4 exposure before betting. Races with multiple short-priced contenders carry higher deduction risk than those with a clear favourite and long-priced field. Betting at SP eliminates Rule 4 concerns entirely, since the starting price already reflects whatever withdrawals occurred.

Keep a Rule 4 reference handy—whether the official scale bookmarked on your phone or a mental approximation of the key thresholds. Knowing that short-priced withdrawals trigger major deductions while 14/1+ non-runners trigger none helps you assess risk before placing your bet rather than after seeing the settlement.