Why prices move before the start
Why prices move before the start
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Last reviewed: 26/10/2026. No tips or predictions, 18+.
Watch any racing broadcast and you'll see a column of numbers beside each runner: the opening price, a string of changes, the current price. Punters call those changes flucs. A horse that shortens is firming; one that lengthens is drifting. A sudden, heavy move in is a plunge.
Big moves don't always mean much. The 2026 Cox Plate's long-time early favourite finished sixth, and the race-day favourite ran third; our Racing page walks through how that market moved.
Prices move for a handful of reasons, and they aren't all "smart money". Here's each one, followed by what happens to a bet when a price moves, a horse is scratched, or a result changes on protest.
Cause 1: Money in, money out
Cause 1: Money in, money out
For a fixed-price operator, every bet changes its position. Say it has taken $20,000 on Runner A at an average of $4. If A wins, it pays $80,000. If that's more than it's comfortable losing, it shortens A, so new bets pay less and fewer people take the price, and may lengthen other runners to attract money elsewhere.
It works like a ticket reseller for a sold-out concert: as more people ask for seats in the same section, the asking price goes up. Nothing about the concert changed; demand did.
On the tote, nobody adjusts the price. The approximate dividend shown before the race is the current pool, less commission, divided by what's on each runner. Every new bet changes the maths, which is why approximates can jump in the last minutes when a lot of money arrives at once.
On an exchange, moves happen when backers and layers disagree. If backers keep taking every available price, the best price shortens. If layers flood in, it drifts.
Cause 2: New information
Cause 2: New information
Some moves happen because the facts changed:
• Track rating. Racing Australia's national scale runs from Firm (1–2) through Good (3–4), Soft (5–7) to Heavy (8–10). A Good 4 is "a track with some give in it"; a Soft 6 is "moist but not a badly affected track"; a Heavy 8 is a "rain affected track that horses will get into". A downgrade after rain can shorten horses with good wet-track records and lengthen others.
• Scratchings. Each withdrawn runner shifts every remaining runner's chances. Racing Australia publishes scratching release times for each meeting.
• Jockey and gear changes, published by the racing body before each meeting.
• Barrier draw, published when the field is finalised.
• Team lists and late withdrawals in AFL and NRL. See the AFL and NRL pages for how those markets react.
• Weather for outdoor sport: wind for goal kicking, dew for night games, rain for totals.
Cause 3: Following the market
Cause 3: Following the market
Operators watch each other and the exchange. If a horse shortens on the exchange because matched bets keep coming, any operator that hasn't moved is now offering more than the market and will usually follow fast. That's why a big move shows up across many operators within minutes.
Cause 4: The book tightens
Cause 4: The book tightens
Early markets often carry a bigger margin because traders know less. As the start approaches and information and money arrive, many operators trim their margin. That can lengthen several runners at once without any of them being specifically opposed.
What happens to a bet when the price moves?
What happens to a bet when the price moves?
It depends on which system you used.
Fixed odds and matched exchange bets lock in; tote and SP bets keep moving until the start.
Scratchings and deductions, with numbers
Scratchings and deductions, with numbers
This is the part that catches most people out on Melbourne Cup day.
Why deductions exist. When fixed-price wagering opens, prices assume a full field. Scratch a runner and every remaining runner's chance improves. Anyone holding an earlier price on another horse now has a price bigger than the new field deserves. To correct that, fixed-price bets placed before the scratching can have their return reduced by a deduction, quoted in cents per dollar. The shorter the scratched runner was, the bigger the deduction; a $2 favourite produces a large one, a $101 outsider a tiny one or none.
A worked example (our illustration):
• A $10 fixed-price bet on Runner B at $6.00 has a potential return of $60, of which $50 is winnings. (Example only, not a tip.)
• A short-priced rival is then scratched and a 20-cent deduction applies.
• Applied to winnings only: $50 × 0.80 = $40 winnings, so $50 back in total.
• Applied to the total return: $60 × 0.80 = $48 back in total.
Operators publish their own deduction tables and don't all apply them the same way: some apply the deduction to the full face value of the ticket, others to winnings only. Check the operator's rules; the deduction for each race normally appears on its result page.
We worked through both methods side by side because this is exactly where operators' published rules differ, and where the gap in a payout usually comes from.
Timing matters. A deduction applies only to bets struck before the scratching. A bet placed after the scratching is priced on the new field and isn't reduced.
On the tote, bets on a scratched runner are refunded and the pool re-forms around the remaining runners, so there's no deduction. For exotics such as trifectas, the operator's rules decide what happens to a scratched selection.
At SP, there's nothing to deduct: the starting price is set at the jump, after the final field is known.
Protests and correct weight
Protests and correct weight
A bet isn't settled when the horses cross the line. Stewards first confirm the placegetters weighed in correctly, and any protest, a claim of interference, must be decided. If a protest is upheld, placings change and bets are settled on the amended result. Once "correct weight" is declared, payouts follow.
Some operators choose to pay on the first-past-the-post result as well as the amended one. That's a commercial decision, not a rule of racing.
Starting price, defined clearly
Starting price, defined clearly
A bet at SP is settled at the fixed price that stands at the moment the race starts, rather than the price showing when you placed the bet. Historically, SP was the price in the on-course betting ring at the start; today, with most money bet off-course, each operator's wagering rules define exactly which price it uses as SP. In the 2026 Cox Plate, Cosmic Crusader's closing fixed price was $9.50, according to the official results.
The trade-off is simple: at SP the price isn't known until the race begins. If the runner drifts, the bet pays more; if it firms, it pays less.
A myth worth retiring
A myth worth retiring
"A plunge means someone knows something." Sometimes. Often not. A plunge can be one large bet, a syndicate following a model, a tipping service's subscribers backing the same horse at the same time, or a popular runner soaking up casual money on a big day. The movement tells you money arrived. It doesn't tell you why, and it doesn't tell you the result.
Page updates
Page updates
26/10/2026: first published. No changes since.
Sources for this page
Sources for this page
• Racing Australia, Track Ratings — https://t.racingaustralia.horse/FAQ/Track-Ratings.aspx (Accessed 26/10/2026)
• Racing Australia, Scratching Release Information — https://t.racingaustralia.horse/FreeFields/ScratchingReleaseInformation.aspx (Accessed 26/10/2026)
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