You backed a horse at 5/1. It won. You expected six times your stake back, but the slip says something different. A chunk is missing, and there is a line on your receipt you probably skimmed past: Rule 4 deduction applied. That line is the reason your payout shrank, and it has nothing to do with your selection losing form or the bookmaker being greedy. It exists because another horse — one you may not have even noticed on the card — was withdrawn after the market had already formed.
Rule 4 is the mechanism the betting industry uses to recalibrate payouts when a non runner distorts the odds after bets have been placed. The principle is straightforward: if a horse is scratched, the remaining runners become more likely to win, so deductions are applied to reflect that shift. In practice, the system is layered with thresholds, cumulative caps, bookmaker quirks and an entirely separate exchange model that operates under different logic. The gross gaming yield from online horse racing betting in the UK reached £766.7 million in 2024–25, according to the Gambling Commission — and every penny of that passes through a framework where Rule 4 is a constant variable.
This article breaks the system down to its parts. What you actually take home after a deduction depends on odds ranges, the number of withdrawals, and which platform you bet with. By the end, you will know exactly how much can be taken, when, and what you can do about it.
Where Rule 4 Comes From — Tattersalls Committee and the Logic Behind Deductions
The name itself is a clue. Rule 4 is not a bookmaker invention — it comes from the Tattersalls Committee Rules on Betting, specifically Rule 4(c), which has governed the settlement of bets at British racecourses since long before online accounts existed. Tattersalls, originally a bloodstock auction house founded in the eighteenth century, evolved into the arbitration body for disputes between backers and layers on course. Their committee wrote the rules that bookmakers — both on-course and off — still follow today.
The logic behind the deduction is grounded in a simple economic argument. When a punter places a bet at, say, 4/1, the price reflects the full field. Remove one runner — especially a short-priced one — and the probability of every remaining horse winning goes up. Without an adjustment mechanism, bookmakers would be paying out at odds that no longer reflect the true state of the market. More importantly, punters who backed the favourite’s main rival would receive an artificially inflated return.
“There is no silver bullet to tackle the issue of non-runners. We need to balance the needs of trainers, owners, jockeys and staff with those who watch and bet on racing,” Richard Wayman, then BHA Chief Operating Officer, said in 2017 when the governing body launched a package of measures to reduce withdrawals. That balancing act runs through every aspect of Rule 4: the scale is designed to be proportional, applying heavier deductions when a heavily-backed horse is scratched and lighter ones — or none at all — when a long shot drops out.
What makes Rule 4 distinct from a general non-runner refund is scope. If your horse is the one withdrawn, your bet is voided and your stake returned. Rule 4 does not touch your stake — it touches your winnings. It applies when someone else’s horse is taken out, and you still win. That distinction trips up a surprising number of bettors who conflate the two, expecting either a full payout or a full refund and ending up with neither.
The Tattersalls framework also sets the ceiling. No matter how many horses are withdrawn, the combined deduction can never exceed 90p in the pound. That cap protects bettors from scenarios where multiple non runners in a small field could, theoretically, wipe out the entire profit. Whether that cap feels generous depends on your perspective — losing 90% of your winnings is still a brutal hit, even if it is technically capped.
The Full Deduction Scale — From 90p Down to Zero
The Rule 4 deduction scale is tied to the starting price of the withdrawn horse. The shorter the odds of the non runner, the larger the deduction from your winnings. This makes intuitive sense: a 1/2 favourite being scratched reshapes the entire market, while a 33/1 outsider disappearing barely moves the needle.
At the top of the scale, a horse priced at 1/9 or shorter triggers a 90p deduction — meaning for every pound of profit you would have earned, you keep just 10p. At the other end, a non runner priced between 10/1 and 14/1 produces only a 5p deduction. Beyond 14/1, there is no deduction at all; the assumption is that such a long shot carried too little market weight to meaningfully affect other runners’ chances.
The scale moves in steps, not on a sliding gradient. A non runner at 2/5 produces a 65p deduction. One at evens triggers 45p. At 5/2, the deduction drops to 30p; at 5/1, it falls to 20p; at 9/1, it is 10p. Each step corresponds to an odds bracket, and the bookmaker applies the deduction that matches the withdrawn horse’s starting price at the time of withdrawal — not the price when you placed your bet.
This is a critical detail that catches many punters off guard. If you backed your horse early in the morning and a rival was scratched at noon, the deduction is calculated against that rival’s SP at withdrawal, not the price it was showing when your bet went on. In markets that move significantly between opening and the off, this means the deduction you face can be very different from what you might have estimated.
Understanding the brackets also reveals something useful about risk. If the withdrawn horse was hovering on the boundary between two deduction bands — say, drifting from 3/1 to 4/1 — a small price movement determines whether you lose 25p or 20p in the pound. For larger stakes, that 5p difference per pound adds up fast. Professional punters track these boundaries not because they can control them, but because knowing them allows better assessment of what you actually take home after a non runner event.
Rule 4 Deduction Table by Odds Range
The full scale runs across roughly twenty bands. At the very top, a withdrawn horse priced at 1/9 or shorter costs you 90p from every pound of profit — nearly the entire return. From there the deduction steps down through the odds: 80p at around 1/4, 70p at 1/3, 60p at 1/2, 55p around 8/13, and 50p at 4/5. Cross the evens line and the hit drops to 45p. At 5/4 to 6/4 the deduction is 40p; at 13/8 to 7/4, 35p; at 15/8 to 9/4, 30p.
The bands keep thinning as the odds lengthen. A non runner at 5/2 to 3/1 means a 25p deduction. At 10/3 to 4/1 it falls to 20p. Between 9/2 and 6/1 you lose 15p in the pound; between 13/2 and 9/1, just 10p. The smallest active band — 10/1 to 14/1 — carries a 5p deduction, and anything over 14/1 triggers no deduction at all. The market considers such long shots too insignificant to warrant an adjustment.
Two details are worth highlighting. First, the 45p band covers a wide stretch from 5/6 through to 6/5, meaning horses on either side of evens attract exactly the same deduction — a quirk that occasionally surprises punters expecting a cleaner break at the even-money mark. Second, the practical reality of the 5p band is softer than the rules suggest: several major bookmakers choose not to apply the minimum deduction when only one non runner falls in the 10/1 to 14/1 range, a point covered in the bookmaker exceptions section below.
When Multiple Horses Are Withdrawn — Cumulative Rule 4
A single non runner is straightforward: one withdrawal, one deduction. But racing regularly serves up mornings where two, three, or even four horses come out of the same race. Soft ground arrives overnight, a virus sweeps through a yard, or going changes push multiple trainers to scratch on the morning of the race. In those situations, Rule 4 deductions are cumulative — but with a hard ceiling.
The maths works by adding individual deductions together. If one non runner triggers a 25p deduction and another triggers a 15p, the total applied to your winnings is 40p in the pound. Three withdrawals at 20p, 10p and 10p would produce a combined 40p deduction. The principle is additive, not multiplicative — each horse’s deduction is calculated independently, then the values are summed.
The cap matters most in smaller fields. Imagine a seven-runner handicap where three horses are withdrawn before the off. If the combined deduction exceeds 90p in the pound, it is capped at 90p regardless. You would still receive at least 10% of your net winnings, no matter how dramatic the carnage. Without that ceiling, certain scenarios — a strong favourite plus two second-tier horses all coming out — could theoretically push the total deduction past 100%, which would be absurd. The Tattersalls framework prevents it.
Where cumulative deductions sting most is in competitive handicaps during the winter months. Jump racing in early 2024 saw an extraordinary proportion of soft and heavy ground — and with it, clusters of withdrawals. A punter backing a 6/1 shot in a twelve-runner handicap could end up facing a 50p or 60p total deduction if three or four rivals were scratched, leaving a watered-down field and a drastically reduced payout even on a winning bet.
Worth noting: the cumulative deduction is calculated at the time each horse is removed. If one horse is taken out at 9am and another at 11am, the bookmaker determines the SP bracket for each at their respective withdrawal time. The prices may have shifted between those two moments, so the deduction is not simply a snapshot of the early-morning market. It is a layered calculation, and that layering can work for or against you depending on how the market moved.
Bookmakers That Waive the 5p Deduction
Not every operator follows the Tattersalls scale to the letter. In a competitive market, the 5p deduction — the smallest band, applied when a non runner was priced between 10/1 and 14/1 — has become a point of differentiation. According to Geegeez, several major bookmakers including bet365, Coral, Ladbrokes and William Hill choose not to apply the 5p deduction as a goodwill gesture to customers when a single non runner falls into that range.
The reasoning is partly commercial, partly practical. A 5p deduction on a £10 win takes 50p off the payout. It is a small amount that generates disproportionate frustration — customers notice the deduction line on their slip, feel short-changed, and might switch to a competitor who absorbs the hit. From the bookmaker’s perspective, the cost of waiving that deduction across thousands of bets is marginal compared to the retention benefit.
There is a catch, though. The waiver typically applies only when a single non runner triggers the 5p band. If two horses are withdrawn and their combined deduction is, say, 5p plus 10p, the cumulative 15p is applied in full. The goodwill gesture does not extend to multi-withdrawal scenarios, even if one of the individual components is 5p. Each bookmaker’s terms differ slightly in this area, so it is always worth checking the specific Rule 4 policy on your operator’s site before assuming the deduction will be dropped.
Smaller or newer bookmakers, including many that operate on thinner margins, tend to apply the full Tattersalls scale without exception. If you regularly bet with independent operators or lesser-known brands, expect the 5p deduction to land every time. The waiver is a luxury of the big four, funded by volume and customer acquisition budgets that smaller firms do not have.
Worked Examples — Calculating Your Adjusted Payout
Numbers settle arguments. Here are three scenarios that show exactly what happens to your returns under different Rule 4 conditions.
Example One: Single Non Runner, Short-Priced
You place £20 on a horse at 4/1 in a ten-runner maiden. Before the off, the 6/4 second favourite is withdrawn due to a going change. The 6/4 price falls in the 5/4 to 6/4 bracket, which triggers a 40p deduction. Your horse wins. Without the deduction, the profit would be £80 (£20 × 4). With the deduction: £80 minus 40% of £80 = £80 − £32 = £48 profit. You receive £48 plus your £20 stake back, totalling £68. The deduction cost you £32 — nearly half the winning margin.
Example Two: Single Non Runner, Long-Priced
Same race, but this time the withdrawn horse was a 12/1 outsider. That falls in the 10/1 to 14/1 band: a 5p deduction. Your profit at 4/1 on a £20 stake is £80 before deductions. After applying the 5p rule: £80 minus 5% of £80 = £80 − £4 = £76 profit. You receive £96 total. The difference is £4 — barely noticeable. And if your bookmaker waives the 5p, you get the full £100.
Example Three: Multiple Non Runners, Cumulative Deduction
This is where things compress. You back a 6/1 shot at £50 in a twelve-runner handicap hurdle. Three horses are withdrawn: one at 3/1 (25p deduction), one at 7/1 (10p) and one at 12/1 (5p). The cumulative deduction is 25p + 10p + 5p = 40p. Your gross profit at 6/1 on £50 is £300. After the 40p deduction: £300 minus 40% = £300 − £120 = £180 profit. You receive £230 instead of £350. That £120 gap is the price of three non runners in a single race — and it is larger than many punters expect when they first encounter cumulative deductions.
In each case, the arithmetic is identical: calculate the gross profit, apply the combined deduction as a percentage, subtract. The stake is never touched. What changes is the magnitude of the hit, and that depends entirely on the starting price of the withdrawn horse — not on your selection or your odds.
These examples also highlight why tracking the morning market is useful even if you are not betting early. If a 2/1 shot is drifting toward 3/1 at the time of withdrawal, the difference between a 30p and a 25p deduction is five percentage points of your profit. On a big-staked winner, that shift represents real money.
Rule 4 vs Betfair Reduction Factor — Two Different Systems
If you bet on the exchanges rather than with traditional bookmakers, Rule 4 does not apply. Betfair and other betting exchanges use a different mechanism — the Reduction Factor — to handle non runners, and the differences matter more than most punters realise.
The Reduction Factor is calculated based on the withdrawn horse’s percentage share of the exchange market at the time of removal. It is not a fixed scale tied to odds brackets; it is a dynamic figure derived from how much of the total market the non runner represented. If a horse trading at 3.0 (2/1) on the exchange accounted for roughly 33% of the implied probability in the market, a Reduction Factor of approximately 33% would be applied to winning payouts. The reduction is calculated against each individual market, not against a generic industry table.
One significant difference: Betfair does not apply the Reduction Factor if it falls below 2.5%. In practice, this means any horse whose implied market share is less than 2.5% — roughly equivalent to a 40/1 shot or longer — is treated as immaterial. No adjustment is made. Compare that with traditional Rule 4, where horses up to 14/1 still attract a 5p deduction. On exchanges, the threshold for triggering any deduction at all is considerably higher.
The practical consequence is that exchange punters are less exposed to small deductions from outsider withdrawals. If you laid or backed a horse and a 25/1 outsider is scratched, the exchange settles your bet at the original price. Traditional bookmakers, however, might still apply a 5p Rule 4 on a horse at 12/1 — a much shorter price than the exchange’s 40/1-equivalent threshold.
Conversely, when a short-priced horse is removed, the exchange Reduction Factor can exceed the equivalent Rule 4 step. A strong favourite trading at 1.5 on Betfair might carry a Reduction Factor of 60–70%, whereas the Tattersalls scale would cap the deduction at 60p for that same odds bracket. The exchange model is more elastic in both directions: lighter on longshots, potentially heavier on favourites.
There is also a timing difference. The Betfair Reduction Factor is calculated at the moment the horse is removed from the market, using the exchange’s own pricing data. Traditional Rule 4 uses the starting price as determined by on-course bookmakers or the industry SP calculation. These two reference points can diverge, especially in fast-moving markets where exchange prices lead on-course rails bookmakers by several minutes.
For punters who split their activity between exchanges and traditional books, understanding which system applies — and when one is more favourable — is a genuine edge. Neither system is universally better; it depends on the price of the withdrawn horse and the state of the market at the time of withdrawal.
How to Limit Your Exposure to Rule 4 Deductions
You cannot prevent non runners. What you can do is structure your betting in a way that reduces the damage when they happen — and they will happen, regularly. Total betting turnover on British racing fell roughly 6.8% year-on-year in 2024, according to BHA’s full-year report, and part of the erosion in returns comes from deductions that punters could have managed better.
The most direct protection is timing. Betting as close to the off as possible reduces the window in which a non runner can be declared after your bet is placed. If you bet at 10am and a horse is withdrawn at 1pm, Rule 4 applies to your bet. If you bet at 1:25pm for a 1:30 race and all withdrawals have already been announced, your payout reflects the actual field. The trade-off is obvious: early prices are often better than SP, and waiting means accepting whatever the market gives you at the off. But if the race has known soft-ground concerns or a yard with recent illness rumours, waiting has tangible value.
Another approach is to target races with lower non-runner risk. Flat racing on good ground in midsummer produces fewer withdrawals than a winter handicap hurdle on soft ground. Premier racedays at well-maintained courses attract confirmed runners more reliably than Monday cards at smaller tracks. This is not a guarantee, but it tilts the probability in your favour.
Exchange betting offers a structural advantage in some scenarios. As covered above, the Betfair Reduction Factor ignores withdrawals from long-priced horses that barely register in the market. If you are backing a horse in a large field where several outsiders might drop out, the exchange is the cleaner option — you avoid the drip of 5p and 10p deductions that traditional bookmakers apply from the Tattersalls scale.
Non Runner No Bet promotions are another layer of defence, though they protect your stake rather than your winnings. NRNB is most useful for ante-post markets — where, without it, a withdrawal means total loss of stake with no refund. If you are betting weeks before a festival, NRNB removes one of the biggest risks in the market. It does not eliminate Rule 4 on your winning bets at the off, but it ensures you are not out of pocket on a horse that never runs.
Finally, understand the specific rules of your bookmaker. The differences between operators — who waives the 5p deduction, who applies it; how each settles cumulative deductions; whether they reference SP or withdrawal-time odds — are not academic. Over a season of betting, these small edges compound. What you actually take home is not determined by the headline odds alone. It is determined by the framework around those odds, and Rule 4 is the single biggest variable in that framework.