Rule 4 Deductions in Horse Racing — How Non-Runners Cut Your Payout

You backed a horse at 5/1. It won. You expect six times your stake. Instead, the payout slip shows something less — sometimes significantly less — and the only explanation is a small note: Rule 4 deduction applied. Welcome to the part of horse racing that nobody explains until it costs you money.

Rule 4, formally known as Tattersalls Committee Rule 4(c), exists to recalibrate the market after a non-runner reshapes the field. When a horse is withdrawn, the remaining runners become more likely to win, and bookmakers are entitled to adjust payouts accordingly. The mechanism is a pence-in-the-pound deduction from your winnings, scaled to the odds of the withdrawn horse. The shorter the price of the non-runner, the bigger the bite from your return. That scale runs from 5p in the pound all the way up to 90p — meaning, in the worst case, you lose 90% of your profit.

The price you saw is not the price you get. That is the fundamental reality of betting in a sport where fields change between the moment you place your wager and the moment the stalls open. Rule 4 is not a penalty. It is not a bookmaker trick. It is the mathematical consequence of a smaller field. But understanding exactly how it works — when it applies, when it does not, and how multiple withdrawals compound — is the difference between accepting your adjusted return and questioning whether you have been short-changed.

This guide breaks down the full deduction scale, walks through worked examples, and explains the timing rules that determine whether Rule 4 touches your bet at all. If you bet on British racing, this is the maths you need.

How Rule 4 Works — From Withdrawal to Deduction

The logic of Rule 4 starts with a simple observation: odds reflect the number of runners in a race. If a 12-runner handicap loses two horses before the off, the probability of each remaining horse winning increases. The bookmaker priced the race with twelve runners in mind. With ten, those prices are too generous. Rule 4 corrects this by deducting a fixed amount from your winnings — not from your stake — based on the odds of the withdrawn horse at the time of withdrawal.

Here is the sequence. A horse is declared a non-runner. The bookmaker identifies the starting price (or the price at the time of withdrawal, depending on when your bet was struck) of the non-runner. That price maps to a deduction rate on the Tattersalls scale — expressed in pence per pound of winnings. Your adjusted return is then calculated by reducing your profit by that percentage.

Suppose you placed a £10 win bet at 4/1 on a horse that goes on to win. Without Rule 4, your return is £50 (£40 profit plus your £10 stake). Now suppose a horse priced at 3/1 was withdrawn before the race. The Rule 4 deduction for a 3/1 non-runner is 25p in the pound. That means 25% of your £40 profit — £10 — is deducted. Your adjusted return becomes £40 instead of £50. Your stake is always returned in full; Rule 4 only touches the profit.

This is worth emphasising because it is the most common misunderstanding. Rule 4 does not reduce your stake. If your horse loses, you lose your stake regardless — Rule 4 is irrelevant. It only matters when your selection wins (or places, in each-way bets). The deduction applies to the profit portion of your return.

One more nuance: the deduction is calculated on the winnings at the odds you took, not at the starting price. If you took 6/1 in the morning and the horse drifted to 10/1 by the off, your profit is calculated at 6/1 — and the Rule 4 deduction is applied to that figure. The only variable that comes from the non-runner is the deduction rate itself, which is set by the non-runner’s price.

The system is deliberately mechanical. There is no discretion involved, no judgment call by the bookmaker. The Tattersalls scale provides a fixed lookup: price of the non-runner in, deduction rate out. This is what makes it predictable — and, with a bit of homework, something you can calculate before the bookmaker does.

The Full Deduction Scale — Price vs Pence in the Pound

The Tattersalls Rule 4(c) deduction scale is a fixed table. It has not changed in its fundamental structure since the last major revision in 2010, though the principle dates back to 1886. Every price bracket maps to a single deduction figure, expressed in pence per pound of winnings. Here is the complete scale:

Two things stand out immediately. First, the scale is not linear. The jump between 2/1 (30p) and Evens (50p) is enormous compared to the jump between 5/1 (15p) and 4/1 (20p). This reflects the outsized market impact of losing a short-priced runner — an odds-on favourite being withdrawn reshapes the race far more than a 10/1 shot disappearing.

Second, there is a cut-off. Horses priced over 14/1 at the time of withdrawal trigger no deduction at all. The rationale is straightforward: a 20/1 or 33/1 shot carries such a small share of the market that its removal has negligible effect on the remaining probabilities. In practice, this means that if the rank outsider in a big-field handicap is scratched, your payout stays untouched.

The maximum deduction from any single non-runner is 90p in the pound, corresponding to the withdrawal of a very short-priced favourite (1/9 or shorter). And there is a critical ceiling: regardless of how many horses are withdrawn, the total cumulative deduction can never exceed 90p in the pound. If three non-runners produce deductions of 45p, 25p, and 25p, the combined figure is capped at 90p — not 95p. You always keep at least 10p of every pound of winnings, no matter how decimated the field becomes.

Reading the table is simple once you know the principle: find the price of the non-runner, read across, subtract that number of pence from every pound of your profit. But races rarely lose just one horse — and when multiple non-runners stack up, the arithmetic gets heavier.

Multiple Non-Runners — How Deductions Stack

One non-runner is annoying. Two starts to hurt. Three in the same race can turn a profitable afternoon into a lesson in arithmetic. When multiple horses are withdrawn from a single race, each non-runner triggers its own Rule 4 deduction, and those deductions are added together — up to the 90p cap.

The stacking is additive, not compounding. If Horse A (3/1, 25p deduction) and Horse B (5/1, 15p deduction) are both withdrawn, the combined deduction is 40p in the pound. You do not apply 25p first and then 15p to the remainder. You take the total — 40p — and apply it once to your full profit. This is a meaningful distinction, because compounding would produce a different (and larger) reduction.

Let us walk through a scenario. You have a £20 win bet at 7/2 on a horse in a ten-runner race. Three horses are withdrawn: one at 2/1 (30p), one at 4/1 (20p), and one at 12/1 (5p). The combined deduction is 55p in the pound. Your horse wins. Without deductions, your profit would be £70 (£20 at 7/2). After a 55p deduction, you lose 55% of that profit: £38.50. Your adjusted return is £20 stake plus £31.50 profit — a total of £51.50 instead of £90.

That example illustrates why the 90p cap matters. Imagine a small-field race — six runners — where the 4/5 favourite and the 2/1 second favourite are both withdrawn. That is 55p plus 30p: 85p. If a third horse at 4/1 also goes, you reach 105p. The cap kicks in, so the deduction stays at 90p. You keep 10% of your profit. It is thin, but it is something.

In big handicaps, multiple non-runners are common, particularly when the going changes. A soft-to-heavy switch at Haydock on a Saturday afternoon can pull three or four horses from a 16-runner field, and suddenly the Rule 4 combined deduction is 35p or 40p. If you are betting accumulators with legs in that race, the deduction feeds through to the entire multi — shrinking returns across every fold.

The practical lesson is simple but often ignored: check how many withdrawals have already been declared before placing your bet. If the field has already lost two short-priced horses, the remaining prices may have shortened at the bookmaker — but if you took your price before the withdrawals, Rule 4 will claw back part of the value you thought you had locked in. Sometimes it is better to wait and take the post-withdrawal price with no deduction than to grab the early price and accept the Rule 4 hit. The maths depends on the specific numbers, and the next sections give you the tools to work it out.

Timing Matters — When Rule 4 Kicks In and When It Doesn’t

Rule 4 does not apply to every bet affected by a non-runner. The critical variable is when you placed your bet relative to when the horse was withdrawn. This is where the system gets genuinely interesting — and where a surprising number of bettors get caught out.

The general principle: if a horse is withdrawn after you placed your bet, Rule 4 applies. The bookmaker could not have known the field would shrink, so your odds were set for a larger field and need adjusting. But if the horse was withdrawn before you placed your bet, the bookmaker has already repriced the remaining field. The new odds account for the absence, and no deduction is needed.

This creates a clear dividing line. Check the timestamp of the non-runner announcement (available on the Racing Post app, the BHA’s own feed, or your bookmaker’s race card). Then check when your bet was placed. If your bet predates the withdrawal, expect a deduction. If it came after, you are clean — the price you took already factors in the smaller field.

There are edge cases. Bets taken at starting price (SP) are settled at the final market price, which by definition incorporates all non-runners declared before the off. SP bets therefore carry no Rule 4 deduction for any non-runner declared before the race, even if the horse was withdrawn five minutes before the start. Rule 4 on SP bets only kicks in for horses withdrawn after the final show of odds — which in practice means at-the-stalls withdrawals.

And this is where the 2024 rule change comes in. Since 1 May 2024, BHA stewards have had the power to declare a horse a non-runner after the stalls have opened, under the revised Rule (H)6. Previously, if a horse planted itself in the stalls and refused to jump, it would still be classified as a runner — and you would lose your bet. Now, the stewards can deem that horse a non-runner if it was denied a fair start. Brant Dunshea, the BHA’s Chief Regulatory Officer, described the change as “a positive development for participants and bettors.” The implication for Rule 4 is clear: a post-stalls non-runner will trigger a deduction on all pre-race bets, including SP bets, because the withdrawal happened after the market closed.

Ante-post bets sit at the other extreme. If you backed a horse weeks or months before a race (at ante-post prices), and that horse becomes a non-runner, you do not get Rule 4 protection — or any protection at all. Ante-post bets are all-in, run-or-not. The horse does not run, you lose your stake, end of story. Rule 4 is a race-day mechanism, and it does not reach back to ante-post markets.

So the timing hierarchy, from most protected to least, runs: SP bet (deduction only for post-close withdrawals) → fixed-price bet placed before withdrawal (deduction applies) → fixed-price bet placed after withdrawal (no deduction, adjusted price already taken) → ante-post bet (no protection whatsoever).

SP Bets vs Early-Price Bets — Different Deduction Outcomes

The choice between taking an early price and leaving your bet to starting price has always involved trade-offs — value versus certainty, opinion versus the crowd. Rule 4 adds another dimension to that calculation, because the two bet types interact with non-runner deductions in fundamentally different ways.

When you take an early price — say, 8/1 at 10am for a 3.30 race — you are locking in that number. If a non-runner is declared at 2pm, your profit will be calculated at 8/1, but the Rule 4 deduction will eat into that profit. Depending on the price of the withdrawn horse, you might lose 15p, 25p, or more from every pound of winnings. The horse you backed might have shortened to 5/1 by the off because the market adjusted to the withdrawal, but you are still paid at 8/1 minus the deduction. Whether that leaves you better or worse off than 5/1 with no deduction depends on the specific numbers.

Contrast this with an SP bet. The starting price is determined by on-course bookmakers immediately before the race, incorporating every non-runner that has been declared up to that point. Your SP bet is settled at that final price, with no Rule 4 deduction for pre-race withdrawals. The market has already done the adjusting for you.

Here is a worked comparison. You like a horse in a nine-runner race. The morning price is 6/1. A rival at 3/1 is withdrawn at noon. The Rule 4 deduction is 25p in the pound. By the off, your horse’s SP has shortened to 9/2.

If you took 6/1 early: your profit on a £10 bet is £60, minus 25% = £45. Total return: £55. If you took SP at 9/2: your profit is £45, no deduction. Total return: £55. In this hypothetical, the numbers are identical — but they rarely are in practice. Often the SP adjusts by less than the Rule 4 deduction implies, especially in big fields where the non-runner’s market share is absorbed unevenly across the remaining horses. In those cases, the early price minus Rule 4 can still beat the SP.

The reverse is also true. In small fields with a short-priced non-runner, the SP of the remaining horses adjusts dramatically. Your early 3/1 with a 45p deduction may return significantly less than the SP of 6/4 with no deduction. Small fields amplify the impact of every withdrawal, and early-price bettors feel that amplification through Rule 4.

There is no universal answer to which approach is better. The decision depends on field size, the likely price of potential non-runners, and how confident you are that the early price represents genuine value over the probable SP. What Rule 4 adds to the equation is this: taking an early price is not risk-free even when your horse wins. The field can change, and the deduction follows.

Tattersalls Committee — The 1886 Rules That Still Govern Payouts

Rule 4 did not emerge from a modern regulator’s office. It was born at Tattersalls, the bloodstock auctioneers whose premises at Hyde Park Corner served as the unofficial court of British betting disputes for more than a century. The Tattersalls Committee Rules on Betting were codified in 1886, and they remain the foundation of how winning bets are settled in British horse racing today. The last significant revision came in 2010 — 124 years after the original drafting.

The Committee originally comprised senior figures from the racing and betting worlds who gathered to settle disputes between backers and bookmakers. Before these rules existed, every disagreement over a non-runner, a dead heat, or a walkover was argued ad hoc, sometimes with fists. The 12 rules that Tattersalls formalised gave the sport a shared framework: what constitutes a valid bet, when a bet is void, how dead heats are settled, and — crucially — what happens when a horse is withdrawn after the market has formed.

Rule 4(c) is the one that governs deductions. Its original phrasing has been refined, but the principle is unchanged: when a runner is withdrawn from a race after bets have been struck, the bookmaker is entitled to make a deduction from the winnings of all bets placed before the withdrawal. The size of the deduction is pegged to the odds of the withdrawn horse, on the logic that a shorter-priced non-runner distorts the remaining market more than a longer-priced one.

What is remarkable is how little the mechanism has evolved. The pence-in-the-pound scale has been adjusted — the 2010 revision tightened some of the brackets — but the conceptual architecture is Victorian. There is no algorithmic recalculation, no dynamic repricing based on exchange data, no machine learning. It is a fixed lookup table, applied by hand (or, these days, by software that replicates the hand calculation). In an era of sub-second exchange trading and real-time probability models, the Tattersalls approach is a deliberate anachronism — and it works precisely because it is simple enough that every bookmaker, every bettor, and every regulator can agree on the result.

The Betfair Exchange, launched in 2000, introduced a parallel system — the reduction factor — which uses a different methodology. But the traditional bookmaker market still settles by Tattersalls, and that means the majority of bets placed on British racing are governed by rules written when Queen Victoria was on the throne. If you ever feel that Rule 4 is an archaic inconvenience, you are not entirely wrong. But its longevity is itself a kind of endorsement. Simplicity and transparency have kept it in place for nearly 140 years.

Worked Examples — Calculating Your Adjusted Return

Theory is useful. Arithmetic is better. Here are four scenarios that cover the most common Rule 4 situations you will encounter. Each one follows the same three-step process: identify the deduction rate, calculate the profit before deduction, and subtract the deduction from the profit — never from the stake.

Single Non-Runner, Win Bet

You place a £25 win bet at 5/1 on Blue Sapphire in the 2.30 at Newbury. An hour before the race, the 2/1 favourite Desert King is withdrawn. The Rule 4 deduction for a 2/1 non-runner is 30p in the pound.

Without deduction: profit = £25 × 5 = £125. Total return = £150 (profit plus stake). With Rule 4: deduction = £125 × 0.30 = £37.50. Adjusted profit = £87.50. Total return = £112.50. You have lost £37.50 of profit — nearly a third — because the withdrawn horse was relatively short. If the non-runner had been a 10/1 outsider instead, the deduction would have been just 10p: £12.50, leaving you with £137.50.

Single Non-Runner, Each-Way Bet

You place a £10 each-way bet (£20 total) at 8/1 on Harbour Town in a 12-runner handicap. A horse priced at 4/1 is withdrawn. Rule 4 deduction: 20p in the pound. Harbour Town finishes second. The each-way terms are 1/4 the odds for the first four places.

The win part of your bet loses — Harbour Town did not win. Your place part pays at 8/1 divided by 4 = 2/1. Place profit = £10 × 2 = £20. Rule 4 deduction on the place profit = £20 × 0.20 = £4. Adjusted place profit = £16. Total return = £10 (place stake) + £16 = £26. From a total outlay of £20, you make £6 profit instead of £10. The deduction applies separately to the win and place portions — if Harbour Town had won, both the win profit and the place profit would each be reduced by 20p in the pound.

Two Non-Runners, Win Bet

You place a £50 win bet at 3/1 on Midnight Storm. Two horses are withdrawn: one at 5/2 (25p deduction) and one at 6/1 (15p deduction). Combined deduction: 40p in the pound.

Profit before deduction = £50 × 3 = £150. Deduction = £150 × 0.40 = £60. Adjusted profit = £90. Total return = £140 instead of £200. Two non-runners at middling prices have taken 40% of your profit — enough to turn a good day into a mediocre one. Had the second non-runner been priced at 16/1 instead of 6/1, there would have been no additional deduction (over 14/1 = exempt), and your total return would have been £162.50.

Near-Maximum Deduction Scenario

This is the worst case that realistically occurs. You are betting on a six-runner novice chase. You take 5/1 about the outsider of the field, £20 win. Three horses are pulled out: the 4/6 favourite (60p), a 3/1 shot (25p), and a 7/1 shot (10p). Combined deduction: 95p — but capped at 90p.

Profit before deduction = £20 × 5 = £100. Deduction = £100 × 0.90 = £90. Adjusted profit = £10. Total return = £30. You backed a 5/1 winner and your total return is barely more than your stake. This is the scenario that tests patience and demands perspective. The field went from six runners to three, and the race was a fundamentally different contest from the one you priced up. Rule 4 is doing what it was designed to do: reflect the reality that a three-runner race and a six-runner race are not the same bet. The 90p cap ensures you cannot finish with less than you started — but only just.

Across all four examples, the lesson is consistent. Short-priced non-runners hurt the most. Multiple withdrawals compound the damage. And each-way bets take the hit on both the win and place portions separately. If you keep these principles in mind, you can estimate your adjusted return before the bookmaker does the maths — and decide, before the off, whether the remaining field still offers value at the price you took.