Rule 4 Deductions Explained – Non Runner Betting Guide UK

You backed a 5/1 shot at 10:30 in the morning. By post time, two rivals have been pulled out, the market has collapsed, and your horse drifts to 3/1 on-course. The bookmaker still has your bet at 5/1 — but the field it was priced into no longer exists. Rule 4 is the mechanism the industry uses to square that circle. It applies a deduction to your potential payout, scaled to the price of the withdrawn horse, so that bookmakers aren’t paying over-the-odds on a race that got significantly weaker.

The logic is straightforward, even if the maths occasionally isn’t. This article walks through the full deduction scale published by the Tattersalls Committee, explains how cumulative deductions work when multiple horses drop out, and runs real-money examples across singles, accumulators and exchange bets. If you’ve ever stared at a settling slip and wondered where part of your winnings went, the answer almost certainly lives somewhere in the next three thousand words.

Know the scale before the off. That single sentence is the difference between a bettor who understands the game and one who feels robbed every time a favourite is scratched.

Where Rule 4 Comes From and Why It Exists

Rule 4 takes its name from the fourth rule in the Tattersalls Committee’s Rules on Betting, which have governed the settlement of wagers on British racecourses for over a century. The Tattersalls Committee itself predates the modern bookmaking industry — it was the original arbiter of disputed bets, sitting in a room at Tattersalls’ auction house in Knightsbridge. By the time high-street betting shops arrived in the 1960s, Rule 4 was already embedded in the DNA of how horse racing markets functioned.

The problem it solves is older than any committee, though. When a horse is withdrawn from a race after the market has formed, the remaining runners become more likely to win — mechanically, not because they got faster, but because there are fewer competitors. A 10-runner race with a 3/1 favourite that loses two no-hopers is still a different proposition from the race the bookmaker originally priced. Without Rule 4, bookmakers would be consistently overpaying on races that had become less competitive after the off-price was set, and that cost would eventually be passed on to punters through worse prices overall.

Richard Wayman, then Chief Operating Officer at the BHA, put the issue plainly in 2017: “Non-runners are a source of frustration to those who watch and bet on the sport, creating uncertainty in betting markets, reducing participation, the number of runners, and the competitiveness of races.” That frustration runs in both directions. Punters hate seeing their returns trimmed. Bookmakers hate settling bets that no longer reflect the actual contest. Rule 4 is the compromise — imperfect, sometimes irritating, but broadly accepted as the least-bad solution to an unavoidable problem.

The scale itself has been refined over the decades, but its core logic hasn’t changed: the shorter the price of the withdrawn horse, the larger the deduction. A horse withdrawn at 1/1 collapses the market far more than one scratched at 14/1, so the deduction is heavier. That graduated approach is what separates Rule 4 from a flat percentage cut — it attempts to match the actual market distortion caused by each specific withdrawal.

The Complete Rule 4 Deduction Scale

The complete Rule 4 deduction scale runs from 90p in the pound down to nothing, determined entirely by the starting price of the withdrawn horse. Here it is, laid out without the ambiguity that most bookmaker help pages seem to enjoy:

When a withdrawn horse’s SP is 1/9 or shorter, the deduction is 90p per pound of winnings. At 2/11 to 2/17, it drops to 85p. From 1/4 to 1/5, the deduction is 80p. The 3/10 to 2/7 band costs 75p. At 2/5 to 1/3, it’s 70p. From 8/15 to 4/9, the deduction is 65p. The 8/13 to 4/7 range carries 60p. Horses withdrawn at 4/5 to 4/6 trigger a 55p cut. The 20/21 to 5/6 band means a 50p deduction. At evens to 6/5, you lose 45p. From 5/4 to 6/4, it’s 40p. The 8/5 to 7/4 range costs 35p. At 9/5 to 9/4, the deduction is 30p. From 12/5 to 3/1, it’s 25p. Between 100/30 and 4/1, you pay 20p. The 9/2 to 11/2 band carries a 15p deduction. From 6/1 to 9/1 it’s 10p, and at 10/1 to 14/1 you’re down just 5p. If the withdrawn horse was longer than 14/1, there’s no deduction at all — the market impact is considered negligible.

A few things jump out from that scale. First, the top end is brutal: a horse pulled out at 1/9 or shorter takes 90p off every pound you would have won. In practice, this means a withdrawn odds-on shot can nearly wipe out your return on paper before the cumulative cap even comes into play. Second, the scale runs through eighteen bands and is not linear. There’s a 5p step between most adjacent bands, but the market distortion it reflects doesn’t follow a neat curve — a withdrawal at 4/6 changes the race far more dramatically than a withdrawal at 9/2, and the graduated structure tries to match that reality.

Third, and this is the detail many punters miss, the deduction is always applied to the winnings portion of your return, not to your total payout including the stake. If you bet £10 at 4/1 and win, your total return would be £50 (£40 profit plus £10 stake). A 20p Rule 4 deduction shaves 20% off the £40 profit, leaving you with £32 plus your £10 stake — a total of £42 rather than £50. Your stake is never touched by Rule 4.

The scale as published by Britishracecourses.org reflects the standard Tattersalls framework. Every licensed bookmaker in Britain settles on these same figures. There’s no proprietary variation, no house edge baked into the deduction — this is industry-wide.

Decimal odds users sometimes struggle to map the fractional bands to their preferred format. Here’s a shortcut: divide the numerator by the denominator to get the decimal minus one. So 4/1 is 5.00 in decimal, and the 20p deduction applies. Any decimal price above 15.00 (equivalent to 14/1) carries no deduction.

Cumulative Deductions — The 90p Ceiling

When two or more horses are withdrawn from the same race, the individual deductions are added together — but the total can never exceed 90p in the pound. That ceiling matters more often than you might think. Take a handicap where two joint-favourites at 5/2 are both pulled out. Each triggers a 30p deduction. Added together, that’s 60p — within the cap and applied in full. But if three well-fancied horses disappear and the individual deductions add up to 110p, the actual deduction applied to your bet is capped at 90p. The extra 20p is absorbed by the bookmaker.

This cumulative rule exists because at some point the deductions would exceed the winnings themselves, which would be absurd — you can’t lose more on deductions than you’d have won. The 90p cap ensures that the bettor always retains at least 10p per pound of profit, even in the most chaotic scenario where half the field drops out.

In practice, the cap bites hardest in big-field handicaps where several withdrawals at shortish prices stack up. A 20-runner handicap that loses three horses at 6/1, 8/1 and 5/1 would accumulate 15p + 10p + 15p = 40p, well under the cap. But if the same race lost runners at 2/1, 5/2 and 3/1, the deductions would be 30p + 30p + 25p = 85p — getting close, and one more scratching could push it to the limit.

There’s a subtlety here that catches people out: the deductions are calculated on the withdrawn horse’s price at the time of withdrawal, not at the morning price or the price you took. If a horse drifts from 2/1 to 5/1 and then gets pulled, the deduction is based on 5/1 — meaning 15p rather than the 30p you might have expected. Conversely, a horse that shortens from 6/1 to 2/1 before being scratched will trigger the heavier deduction. The market moves; the deduction follows.

Worked Example — Rule 4 on a Single Bet

Numbers without context are just noise. Let’s run through a complete example on a single bet so the mechanics are impossible to misunderstand.

You place a £20 bet on Horse A at 5/1 in the 3:15 at Newmarket. Before the off, Horse B — a 3/1 shot — is declared a non-runner due to a going change. The Rule 4 deduction for a horse at 3/1 is 25p in the pound.

Without the withdrawal, your winning return would have been: £20 stake multiplied by 5/1 = £100 profit, plus your £20 stake back = £120 total. With the Rule 4 deduction, the calculation changes. You take the £100 profit and subtract 25% of it: £100 minus £25 = £75. Add your stake back and you receive £95 in total. That’s £25 less than you expected, and the deduction was applied automatically — you don’t opt in, you don’t get a notification before the race. It just appears on the slip.

Now add a second withdrawal. Horse C, a 10/1 outsider, is also scratched. The deduction for 10/1 is 5p. The cumulative deduction becomes 25p plus 5p = 30p in the pound. Your £100 profit is now reduced by 30%, leaving £70 in profit and a total return of £90.

The key takeaway is proportionality. Horse B’s withdrawal at 3/1 cost you £25. Horse C’s withdrawal at 10/1 cost you only £5. The longer-priced the scratching, the smaller the bite — and at 14/1 or bigger, there’s no bite at all. This is why Rule 4 stings most in short-priced markets: the favourite being pulled can take a quarter or more off your winnings in a single stroke.

Remember from the cumulative section: the deduction band is set by the withdrawn horse’s price at the time of withdrawal, not by what you took on your selection. Your early price of 5/1 is what generates the profit; the scratched horse’s price at the moment it was pulled is what determines how much of that profit disappears.

Rule 4 Across Accumulators, Doubles and Trebles

This is where Rule 4 gets genuinely complicated, because accumulators multiply returns across legs — and a deduction in one leg cascades through the rest.

The standard treatment is as follows: if one leg of your accumulator has a non-runner and that horse was your selection, the leg is voided and the accumulator drops down. A four-fold becomes a treble, a treble becomes a double. Your remaining legs still stand, but at reduced overall odds. This is straightforward and handled automatically by every bookmaker.

The trickier scenario is when a non-runner appears in the same race as one of your selections but is not your selection. Your horse still runs, your bet still stands — but Rule 4 applies to the winnings from that leg. The deduction is applied to the returns generated by that specific leg before those returns roll into the next one. In a four-fold, a 25p Rule 4 deduction on leg two means the returns entering leg three are already reduced by 25%. Since accumulators compound, that 25% reduction echoes through every subsequent leg.

Here’s a worked example. You have a treble: Leg 1 at 3/1, Leg 2 at 2/1, Leg 3 at 4/1 — stake of £10. Without any deductions, all three winners would return: £10 multiplied by 4 (Leg 1), then by 3 (Leg 2), then by 5 (Leg 3) = £600 total, of which £590 is profit.

Now suppose a 5/2 shot is withdrawn from the Leg 2 race. The Rule 4 deduction for a 5/2 withdrawal is 25p. Leg 1 is unaffected — your £10 returns £40. Leg 2 now applies Rule 4: the profit portion of the Leg 2 winnings gets docked 25%. Your £40 at 2/1 generates £80 profit. After the 25p deduction, that profit drops to £60. Add back the £40 rolling stake and your total entering Leg 3 is £100 instead of £120. Leg 3 at 4/1: £100 multiplied by 5 = £500. Your final return is £500, down from £600 — a £100 loss to a single Rule 4 deduction on one leg of a treble.

The compounding effect is why seasoned accumulator bettors pay close attention to declarations. A Rule 4 hit early in a multi-leg bet shrinks everything downstream. The same 30p deduction on the final leg would have cost you less in absolute terms, because it wouldn’t have compounded through the remaining selections.

If the non-runner is your selection rather than a rival in the same race, the leg is voided and the accumulator drops down with no Rule 4 applied to that leg — you simply lose the multiplier. A four-fold that loses one selection to a non-runner becomes a treble settled at whatever odds your remaining three horses returned. Most bookmakers process this automatically, though it’s worth checking the settled slip to make sure the void leg was correctly removed rather than treated as a loser.

How Best Odds Guaranteed Interacts with Rule 4

Best Odds Guaranteed is one of the most popular promotions in British racing. The deal is simple: take an early price, and if the starting price is bigger, the bookmaker pays out at the SP instead. It sounds like free money, and often it is. But Rule 4 adds a wrinkle that many punters overlook.

When a non-runner triggers a Rule 4 deduction, BOG still applies — but the deduction is calculated on whichever price the bookmaker is paying you at. If you took 5/1 in the morning and the SP drifted to 7/1, BOG bumps you up to 7/1. The Rule 4 deduction is then applied to the 7/1 return. You’re still better off than you would have been at 5/1 after the deduction, but the deduction itself is larger in absolute terms because it’s calculated on a bigger number.

The scenario where BOG and Rule 4 genuinely clash is when the non-runner was the reason your horse’s price shortened. If a 2/1 rival is scratched, the remaining horses’ odds will typically contract. Your 5/1 shot might be 4/1 by the off. Under BOG, the bookmaker pays you at 5/1 (the better of your early price and the SP). The Rule 4 deduction for a 2/1 withdrawal is 30p. So your £10 bet at 5/1 generates £50 profit, minus 30% = £35 profit, total return £45. Without the non-runner, in a world where you’d have won at 5/1 with no deductions, you’d have received £60. The withdrawal simultaneously helped your horse’s chances and cost you £15 in deductions.

Some bookmakers apply Rule 4 before determining the BOG comparison, others after. The industry standard is to apply the deduction to the settled price — meaning whichever price the bettor actually receives. In most cases this distinction doesn’t matter, but on tight margins it can shift a pound or two. The terms and conditions of each bookmaker’s BOG offer will specify the order of operations; it’s buried in the small print, and it’s worth the three minutes it takes to find it.

Betfair Reduction Factor vs Traditional Rule 4

If you bet on Betfair or another exchange, Rule 4 doesn’t apply to you — at least not in name. Instead, exchanges use a reduction factor, which serves the same purpose through a completely different mechanism.

The Betfair reduction factor is calculated dynamically based on the volume of money matched on the withdrawn horse at the time of withdrawal. When a horse is scratched, Betfair assesses how much of the overall market that horse represented and assigns a percentage reduction to be applied to winning bets in that race. The reduction factor is published immediately after the withdrawal so bettors can see exactly what they’re facing before the race goes off.

The practical differences between Rule 4 and the reduction factor are significant. Rule 4 is based on a fixed scale tied to the withdrawn horse’s SP — the same 3/1 withdrawal always triggers a 25p deduction, regardless of how much money was wagered. The reduction factor, by contrast, reflects actual market activity. A 3/1 shot that attracted heavy trading volume will generate a higher reduction factor than a 3/1 shot that was lightly traded. This makes the exchange approach more responsive to the real market impact of each withdrawal.

There’s a broader context worth mentioning. Research by the National Centre for Social Research found that the top one per cent of racing bettors — roughly 60,000 individuals — generate 52% of all bookmaker revenue from racing. Many of those high-volume bettors operate primarily on exchanges, where the reduction factor’s precision matters more than the blunt-instrument approach of the Tattersalls scale. For the average punter placing a few bets on a Saturday, the difference between Rule 4 and the reduction factor might amount to a few pence. For someone trading five figures a week, it’s the difference between profitability and the other thing.

One more exchange quirk: if you back a horse on Betfair and it’s declared a non-runner, your bet is voided in full — you get your stake back with no deduction. The reduction factor only applies when a different horse in the race is withdrawn. On traditional bookmakers, a non-runner selection is also voided on day-of-race bets, but the same principle applies differently to ante-post wagers, where stakes are typically lost entirely.

Late Withdrawals and the Timing of Deductions

The timing of a withdrawal determines how much chaos it causes. A horse scratched the evening before the race gives the market time to adjust — bookmakers reprice, punters reassess, and by the off the remaining field is priced more or less accurately. A horse pulled out forty minutes before post time is a different animal entirely. The market can’t fully recalibrate in that window, which is precisely why Rule 4 exists.

Late withdrawals — those declared after the final overnight declarations have closed — carry the heaviest market distortion. The bookmaker has already set prices, early-price punters have already locked in their bets, and the each-way terms are fixed based on the declared field size. When a horse drops out at this stage, Rule 4 is the only correction mechanism available.

The BHA has been working to tighten the window in which late withdrawals can occur. According to the BHA Q3 2025 Racing Report, off-time punctuality has improved significantly, with 87.6% of races in Q1 2025 starting within two minutes of the scheduled time — up from 72.7% in 2023. That improvement is partly linked to better management of late non-runners and the processes surrounding them. Fewer last-minute scratchings mean fewer delays at the start, which in turn means fewer situations where Rule 4 deductions are applied in a rush.

For the bettor, the practical lesson is timing. If you see a late withdrawal in a race where you have a bet, check the Rule 4 deduction immediately — it will be published on the bookmaker’s live feed and on racing data services. If the deduction is steep and your expected value has collapsed, you may want to hedge on the exchange or simply accept the reduced return rather than scrambling for alternatives. Late Rule 4 deductions are a cost of doing business in horse racing; the punters who handle them best are the ones who factor them into their staking plans rather than treating them as personal affronts.

Practical Steps to Minimise Rule 4 Losses

Rule 4 deductions are not avoidable in the way that a bad bet is avoidable. They’re structural — baked into the settlement process. But there are concrete steps you can take to reduce their impact on your bottom line.

First, understand the races where Rule 4 bites hardest. Short-priced markets with small fields are the danger zone. A six-runner race where two horses are scratched can easily trigger cumulative deductions of 50p or more. Big-field handicaps, by contrast, tend to produce smaller individual deductions because the withdrawn horses are often longer-priced. The BHA’s Q3 2025 data showed non-runner rates at their lowest since 2022, which is encouraging — but “lowest since 2022” still means thousands of withdrawals across a season.

Second, consider the exchange for races where non-runners are likely. If you suspect a going-sensitive horse will be pulled — and going accounts for roughly 35% of all non-runners according to BHA data — placing your bet on Betfair means you’ll face a reduction factor rather than a fixed-scale deduction. In some cases the reduction factor will be smaller than Rule 4; in others it will be larger. But at least it reflects the actual market impact rather than a predetermined table.

Third, check declarations before committing your stake. Flat declarations close 48 hours before the race, Jump declarations 24 hours. If you’re betting in the morning on an afternoon card, the declaration stage is already past — but late withdrawals can still occur right up until the race. Building a small buffer into your staking to account for potential Rule 4 hits is simply sound bankroll management. If you’re targeting 10% return on investment across a season, Rule 4 deductions might trim that to 8% or 9% — and the punter who planned for 8% will sleep better than the one who didn’t.

Fourth, review settled bets. Bookmakers occasionally make errors in applying Rule 4, particularly in complex accumulators where deductions interact with void legs and BOG adjustments. It takes two minutes to check the maths. If the settled return doesn’t match your manual calculation, the bookmaker’s customer service team will correct it — they’re required to settle according to the Tattersalls rules, and they know it.

Finally, keep perspective. Rule 4 exists because non-runners distort the market. If the rule didn’t exist, bookmakers would price in non-runner risk upfront by offering worse odds across the board. The deduction after the fact is more transparent and more fair than a hidden margin built into every price. Knowing the scale, understanding the maths, and adjusting your approach accordingly — that’s what turns Rule 4 from a nuisance into just another variable in the model.