Rule 4 Calculator — Work Out Your Adjusted Payout After a Non-Runner

Your horse won. The non-runner announcement came and went, you watched the race, and your selection crossed the line first. Now the bookmaker settles your bet and the return is less than you expected. Rule 4 happened — a deduction was applied because the withdrawn horse shortened the market. The question is whether the deduction is correct.

Plug in the numbers, get the answer. A Rule 4 calculator takes three inputs — your stake, the odds of your winning selection, and the price of the non-runner at the time of withdrawal — and produces the adjusted payout in seconds. The deduction scale runs from 5p in the pound for outsiders priced between 10/1 and 14/1 up to 90p in the pound for odds-on favourites at 1/9 or shorter. If the non-runner was priced above 14/1, no deduction applies at all. The scale is fixed by the Tattersalls Committee and has not changed since 2010.

What follows is a step-by-step guide to calculating your adjusted return manually, followed by worked examples that cover the most common scenarios. Whether you use an online calculator or work through the maths yourself, the logic is identical — and understanding the logic means you will spot an incorrect settlement the moment it hits your account.

How to Use the Rule 4 Calculator — Step by Step

The calculation has four steps. Each one is straightforward, and the whole process takes less time than reading this paragraph.

Step one: find the deduction. Look up the non-runner’s price at the time of withdrawal on the Rule 4 deduction table. A horse withdrawn at 3/1 triggers a 25p deduction. At 5/2, the same 25p. At evens, it rises to 45p. At 1/3, it is 70p. The table is fixed — every bookmaker uses the same scale.

Step two: calculate your gross profit. Multiply your stake by the fractional odds. If you staked £10 at 6/1, your gross profit is £60. If you staked £20 at 9/2, your gross profit is £90. This is the profit before any deduction — the figure the bookmaker would have paid without a non-runner in the race.

Step three: apply the deduction. Multiply the gross profit by the deduction expressed as a decimal. A 25p deduction becomes 0.25. On £60 of gross profit, the deduction is £60 × 0.25 = £15. On £90 of gross profit at 45p, the deduction is £90 × 0.45 = £40.50.

Step four: calculate the adjusted return. Subtract the deduction from the gross profit and add your stake. Using the first example: £60 − £15 = £45 adjusted profit. Add the £10 stake back: your total return is £55. The stake is never subject to Rule 4 — only the profit portion is reduced.

That is the entire process. Four steps, one multiplication, one subtraction. If you can find the non-runner’s price on the deduction table, you can calculate your adjusted return before the bookmaker has finished settling the race.

Worked Examples — Short-Price NR, Long-Price NR, Multiple NR

Example one: short-price non-runner. You backed Horse A at 5/1 for £10. The race favourite, priced at 6/4, is declared a non-runner in the paddock. The Rule 4 deduction for a horse at 6/4 is 40p in the pound. Your gross profit is £50 (£10 × 5). The deduction is £50 × 0.40 = £20. Your adjusted profit is £30, and your total return is £40 (£30 plus your £10 stake). Without the non-runner, you would have received £60. The deduction cost you £20 — a significant chunk, because the withdrawn horse was short-priced and its removal heavily distorted the market.

Example two: long-price non-runner. Same bet — Horse A at 5/1 for £10. This time, a 12/1 outsider is scratched. The Rule 4 deduction for a horse at 12/1 is 5p in the pound. Your gross profit is still £50. The deduction is £50 × 0.05 = £2.50. Your adjusted profit is £47.50, and your total return is £57.50. The difference from a clean payout is barely noticeable. This is by design — a 12/1 shot has a small implied probability of winning, and its removal changes the remaining field’s chances only marginally.

Example three: non-runner above 14/1. Horse A at 5/1 for £10 again. A 20/1 outsider is withdrawn. The deduction: zero. Horses priced above 14/1 do not trigger any Rule 4 deduction. Your return is the full £60. The market considers the horse’s impact negligible, and the Tattersalls Committee rules — originally drafted in 1886 and refined over successive revisions — set 14/1 as the threshold above which no adjustment is warranted.

Example four: multiple non-runners. You backed Horse A at 4/1 for £15. Two horses are withdrawn: one at 3/1 (25p deduction) and one at 7/1 (10p deduction). The cumulative deduction is 25p + 10p = 35p. Your gross profit is £60 (£15 × 4). The deduction is £60 × 0.35 = £21. Your adjusted profit is £39, and your total return is £54. Note the cumulative cap: no matter how many non-runners are declared, the total deduction cannot exceed 90p in the pound. If three withdrawals produce individual deductions of 45p, 30p, and 25p, the total is technically 100p — but it is capped at 90p. Your profit can never be reduced by more than nine-tenths.

Example five: each-way bet with Rule 4. You placed £5 each way on Horse A at 8/1, with each-way terms of one-quarter the odds for four places. The win part: £5 at 8/1 = £40 gross profit. The place part: £5 at 2/1 (one-quarter of 8/1) = £10 gross profit. A non-runner at 2/1 triggers a 30p deduction. The win deduction is £40 × 0.30 = £12; the place deduction is £10 × 0.30 = £3. Your adjusted win profit is £28 and adjusted place profit is £7. Total return if the horse wins: £28 + £7 + £10 stake = £45. Without Rule 4, the return would have been £60. Each-way bets are hit twice — once on each part — which is why the impact can feel disproportionately large.

Common Mistakes — Why Your Payout Doesn’t Match the Calculator

The most frequent complaint about Rule 4 settlements is that the bookmaker’s payout does not match the punter’s mental calculation. In most cases, the bookmaker is correct and the punter has made one of three common errors.

The first mistake is using the wrong price for the non-runner. The deduction is based on the horse’s price at the time of withdrawal, not its overnight price, its morning price, or the price you remember seeing on the racecard. If a horse opened at 4/1 overnight and was backed into 5/2 before being withdrawn at 10:30am, the deduction is based on 5/2 (25p), not 4/1 (20p). Bookmakers use the price at the point of removal, and that figure is recorded by the official feed.

The second mistake is applying the deduction to the total return instead of the profit. Rule 4 only reduces profit. Your stake is always returned in full on a winning bet. If you staked £10 and won £70 back (£60 profit + £10 stake), a 25p deduction takes £15 from the £60 profit — not £17.50 from the £70 total. The distinction matters, and getting it wrong inflates the apparent deduction.

The third mistake involves each-way bets. Many punters calculate the Rule 4 deduction on the combined return and wonder why the figures do not reconcile. The correct approach is to treat the win part and the place part as separate bets, apply the deduction to each independently, and then add the results. The deduction percentage is the same for both parts, but it is applied to different profit figures — the win odds and the place odds — which produces two separate reductions. Adding them together gives the total deduction. Missing this step is the single most common reason a punter’s calculation diverges from the bookmaker’s settlement.