How Rule 4 Affects Your Accumulator – Worked Examples

When one leg of an accumulator has a non-runner, that leg is voided. Your four-fold becomes a treble, your treble becomes a double, and your potential payout shrinks — but you are still in the bet. The complication arrives when a second horse is withdrawn from a different race in your accumulator. That withdrawal does not void another leg; instead, it triggers a Rule 4 deduction on the surviving leg, cutting a percentage from your return based on the odds of the withdrawn horse.

One NR does not void the whole acca — but it dents it. This guide walks through the mechanics step by step, with real-money examples showing exactly how Rule 4 deductions work across doubles, trebles and larger folds. If you have ever collected on an accumulator and wondered why the payout was lower than expected, the answer is almost certainly Rule 4.

What Happens to the NR Leg — Void, Not Deducted

The first principle to understand is that a non-runner leg and a Rule 4 deduction are two different things. When your selected horse is declared a non-runner, that leg is voided. It is removed from the accumulator entirely, and the bet continues as if that race never existed. A four-fold drops to a treble. A treble drops to a double. A double drops to a single. Your stake remains the same; only the structure of the bet changes.

Rule 4 enters the picture in the remaining races, not the voided one. If another horse — one you did not back — is withdrawn from one of the surviving races in your accumulator, the bookmaker applies a Rule 4 deduction to your winnings from that race. The Rule 4 scale runs from 90p in the pound for a very short-priced withdrawal (odds of 1/9 or shorter) down to 5p in the pound for a horse withdrawn at 10/1 to 14/1. If the withdrawn horse was 14/1 or longer, no deduction applies at all.

The BHA introduced these measures because non-runners distort the market. As Richard Wayman, then BHA’s Director of Racing, stated in a 2018 statement: “It is essential that we take these steps to reduce the number of non-runners. They are not good for our sport, its fans or its participants.” Rule 4 is the market’s mechanism for correcting that distortion — and in accumulators, it compounds across legs.

Worked Example — Rule 4 on a Double

Suppose you place a ten-pound double. Leg A is a horse at 3/1 at Kempton. Leg B is a horse at 4/1 at Newbury. Both win under normal circumstances, and your return is calculated as: £10 × 4.0 (decimal odds for 3/1) × 5.0 (decimal odds for 4/1) = £200.

Now introduce a non-runner. A second horse in the Newbury race — not your selection, but a rival — is withdrawn at odds of 5/2. Under the Rule 4 scale, a withdrawal at 5/2 triggers a 25p deduction in the pound. Your Leg B payout is reduced by 25 per cent.

The adjusted calculation works like this. Leg A pays normally: £10 × 4.0 = £40 running total. Leg B pays at reduced odds: the original 4/1 profit is £40 × 4.0 = £160 in winnings on Leg B alone, but Rule 4 takes 25 per cent of the profit from that leg. The profit on Leg B is £160 − £40 = £120 profit, and 25 per cent of £120 is £30. So your final return is £200 − £30 = £170 instead of the expected £200.

That thirty-pound difference is the cost of a single non-runner you did not even back. The deduction feels modest on a double, but it scales painfully across larger bets. And if two horses had been withdrawn from the Newbury race instead of one, the cumulative deduction would be larger still, though it can never exceed 90p in the pound from a single race.

Worked Example — Rule 4 on a Treble

Take a five-pound treble: Leg A at 2/1, Leg B at 3/1, Leg C at 5/1. Under normal conditions, the return is £5 × 3.0 × 4.0 × 6.0 = £360.

Now suppose one horse in Leg A’s race is withdrawn at odds of 7/2, triggering a 20p Rule 4 deduction, and a different horse in Leg C’s race is withdrawn at even money, triggering a 45p deduction. Both deductions apply independently to their respective legs.

The Leg A profit (£15 from the original £5 stake progressing at 2/1, producing £15 in profit) is reduced by 20 per cent: £15 × 0.20 = £3.00 deducted. The Leg C profit portion is reduced by 45 per cent of the profit generated at that leg. Working through the chain: the running total arriving at Leg C is £5 × 3.0 × 4.0 = £60, and Leg C’s profit at 5/1 is £60 × 5 = £300 profit, reduced by 45 per cent = £135 deducted.

The exact calculation can vary slightly between bookmakers depending on how they sequence the deductions — some apply them leg by leg, others calculate the total return and then apply deductions proportionally — but the direction is always the same: your return is smaller than the clean payout, and the more legs affected, the deeper the cut. BHA data from Q3 2025 showed non-runner rates at their lowest since 2022, which means the frequency of Rule 4 events is declining, but on any given accumulator, one withdrawal in the wrong race can still make a meaningful dent.

Larger Accumulators — How Cumulative Deductions Stack

In a six-fold or a Lucky 15, the maths becomes harder to track manually because Rule 4 deductions can apply in multiple legs simultaneously. The key rule is that deductions are capped at a maximum of 90p in the pound per race, regardless of how many horses are withdrawn from that race. If three horses are pulled from a single race in your accumulator, the cumulative deduction on that leg cannot exceed 90 per cent of the profit — though getting anywhere near that cap would require multiple short-priced withdrawals, which is rare.

Where larger accumulators really hurt is in the multiplication effect. A 20 per cent deduction on one leg and a 15 per cent deduction on another might seem manageable in isolation, but applied sequentially across a six-fold, they compound. The final return can be noticeably lower than what you expected when you placed the bet, even if every one of your selections won.

The practical takeaway is straightforward. Before placing a large accumulator, check the declarations for each race and note any short-priced rivals that might be vulnerable to withdrawal — horses with known ground preferences running on uncertain going, or entries from trainers with high non-runner rates. If a race in your accumulator has a short-priced horse that looks likely to be scratched, you can either replace that leg or factor the probable Rule 4 deduction into your expected return. Accumulators are exciting because they multiply; Rule 4 is the reminder that the multiplication works both ways.