Arbitrage betting in Australia
An arbitrage bet covers every outcome of one market at different bookmakers, at prices that, on paper, together return more than the total staked, if every leg is accepted at those prices.
By the B337 team. Last updated .
The short answer
- An arbitrage bet, or arb, covers every outcome of one market at different bookmakers, at prices that, on paper, return more than the total staked whichever outcome lands.
- The test is one sum: turn each price into a chance by dividing 1 by it and add them up. Under 100% and an arb is there; over 100% and the bookmakers' margin is in the way.
- In the worked example below, $200.00 split across two prices returns at least $205.70 whichever side wins, a margin of 2.86% before the stakes round to the cent.
- It is not without risk. Both legs have to be accepted at the prices you saw, bookmakers can void and resettle bets under their terms, and an arbing account is easy for a bookmaker to spot and restrict.
What is arbitrage betting?
Arbitrage betting, or arbing, means backing every outcome of the same market at different bookmakers, each at whichever one is paying most for that outcome. If the prices are generous enough, the money comes back whichever way the event goes, on paper: only if both bets are accepted at those prices and both bookmakers settle the event the same way.
Australian bookmakers do not all price a market the same way or move it at the same moment, so they do not always agree. Each sets a margin into its own card: add up the implied chances of every outcome on one bookmaker's card and the total is over 100%. That excess, the overround, is where its margin comes from: a balanced book keeps 1 - 1 / book percentage of the money staked. Take the best price on each outcome from across the market and the total can fall under 100%, which is the whole idea.
The one sum that tests it
A decimal price becomes an implied chance when you divide 1 by it: $2.00 is 50%, $2.40 is 41.7%. Add them up and you have the book percentage:
- Over 100%: no arb. The combined margin is bigger than the disagreement.
- Under 100%: an arb on paper. The margin is 1 divided by the book percentage, minus 1.
Betting involves risk. Bookmakers can restrict or close accounts and void bets, automation can fail, prices move, and a positive expected value (+EV) bet can still lose. Promotions carry each bookmaker's own terms. There is no guarantee of profit. On paper is not in the account: a leg that is refused, part-accepted or voided leaves you holding a single bet. See responsible gambling for limits and support.
How to calculate an arb
Hypothetical prices, chosen to show the arithmetic. Not a real market, a real price or a forecast.
Take a two-way market. One bookmaker has the first outcome at $2.40; another has the second at $1.80. The implied chances are 41.7% and 55.6%. Added unrounded, 1 / 2.40 + 1 / 1.80 = 0.97222, a book of 97.2%, so the margin is 1 / 0.97222 - 1 = 2.86%.
With $200.00 to put on, each leg takes the share of the money that its own implied chance is of the book percentage. For the first leg that is (1 / 2.40) / 0.97222 = 42.9% of the $200.00, which is $85.71; the second leg takes the rest, $114.29.
| Leg | Price | Implied chance | Stake | Returns | Profit |
|---|---|---|---|---|---|
| Bookmaker A | $2.40 | 41.7% | $85.71 | $205.70 | +$5.70 |
| Bookmaker B | $1.80 | 55.6% | $114.29 | $205.72 | +$5.72 |
| Book percentage | 97.2% | $200.00 | Margin 2.86% | ||
Either outcome returns about $205.70 on $200.00 staked, so on paper the position is at least +$5.70 whichever way it goes, which is 2.85% of turnover, if both legs are accepted at these prices.
Why the split matters more than the margin
Put $100.00 on each leg instead and the first outcome returns $240.00 while the second returns $180.00: a +$40.00 win against a $20.00 loss, which is a bet with a side, not an arb. The free arbitrage calculator does the division from the prices you enter, for two to four outcomes.
How little it takes to disappear
Shorten the second price from $1.80 to $1.70, a ten-cent move: 1 / 2.40 + 1 / 1.70 = 1.00490, so the book is 100.49%, the margin of 2.86% becomes -0.49%, and every outcome returns less than the $200.00 staked: -$0.98. The arb dies at $1.714, which is 1 / (1 - 1 / 2.40), so a price that moves between reading the screen and the bookmaker accepting the bet can be the whole position.
Betting involves risk. Bookmakers can restrict or close accounts and void bets, automation can fail, prices move, and a positive expected value (+EV) bet can still lose. Promotions carry each bookmaker's own terms. There is no guarantee of profit. An arb is not settled until both bookmakers settle it, and either can void or resettle under its own terms. An arbitrage or a middle only works if every bet is accepted at the price shown. See responsible gambling for limits and support.
Where arbs come from, and how to find them
They can show up on markets a long way from the start, on lower leagues and smaller sports where fewer bookmakers price the market, and straight after news, when one card has moved and another has not. In Australian markets that can mean AFL and NRL lines around team announcements, or racing after a late scratching. They can close within minutes, as the out-of-line price is corrected.
Two bookmakers disagree
One prices a market early, another is slow to move after team news, a withdrawal or a line change. For a short while the two sides add up to less than 100%.
You compare every price at once
An arb only exists against the best price available on each outcome, so you have to see all of them together.
You check the split, not just the margin
The stakes go on in proportion to each outcome's implied chance. Get the split wrong and a 2% margin becomes a bet with a side.
You place both legs and check both
A bookmaker can take part of a stake or none of it. Place the leg most likely to move or be refused first. If the second will not then go on at a price that keeps the book under 100%, you hold a single bet: keep it or cover it at the best price left, and count what that costs.
One bookmaker's card never shows an arb, because an arb is the disagreement between two cards. That is the job the odds comparison board does, with prices from 40+ bookmakers side by side, and the arbitrage screener runs the sum above over the sports markets on it.
Betting involves risk. Bookmakers can restrict or close accounts and void bets, automation can fail, prices move, and a positive expected value (+EV) bet can still lose. Promotions carry each bookmaker's own terms. There is no guarantee of profit. An arbitrage or a middle only works if every bet is accepted at the price shown. See responsible gambling for limits and support.
Arbitrage betting risks
What turns a margin on a screen into a loss in an account.
Account restrictions
Betting only when one bookmaker is out of line with the rest of the market, straight after a move and at the maximum stake, is a pattern a bookmaker can see in its own records. Australian bookmakers can cut your maximum stake, stop offering you promotions or close the account, under their own terms.
Voided and resettled bets
If one leg of a pair is voided and the other stands, what is left is a single bet at a price that was never meant to stand alone.
The price you get, not the price you saw
Prices move while you place the second leg, and a bet counts at the price the bookmaker accepts. Accepted lower, a thin margin is already gone.
Two sets of settlement rules
Covered both ways on paper, you can still have one leg voided while the other loses, or both legs reduced.
Partial acceptance
A bookmaker can accept less than the stake you asked for, which leaves the position lopsided: it has to be corrected or closed.
Money sitting still
Each leg needs funds already in that account, so much of the bankroll sits idle across accounts, and one frozen account strands its share.
Together they make a screener's margin the best case. Pass on an arb when:
- a ten-cent move on either price would take the book over 100%;
- one price is far out of line with every other bookmaker, which is where obvious-error voids land;
- the two bookmakers settle that market under different rules;
- the money for the second leg is not already in that account.
Bookmaker terms that decide an arb
In practice, arbitrage is decided by what each bookmaker's terms allow. Read them before you start, because they differ, and where a term and this guide differ, the term applies. The ones that matter here:
- Obvious error. Bookmakers reserve the right to void or resettle bets taken at a price they say was wrong, and the leg that looked best is the likeliest error.
- Account ownership and multiple accounts. An account has to be yours, and bookmakers' terms commonly prohibit holding more than one or betting through somebody else's.
- Stake limits and refusal. A bookmaker can decline a bet, accept part of it, or cut your maximum stake, under its terms and, on racing, within the minimum bet limits some racing bodies set.
- Settlement rules. Each bookmaker's own rules decide dead heats, abandonments and retirements, and how it applies the deduction the stewards declare after a late scratching. Two bookmakers can settle one event differently.
- Automated and third-party betting. Many bookmakers restrict or prohibit it, and that includes software placing bets in your account.
The law and a bookmaker's terms are separate questions, and B337 does not give legal advice: if you need to know where you stand, get independent legal advice. Whether an operator may offer betting in Australia can be checked on ACMA's register. For deposit limits, BetStop self-exclusion and support services, see responsible gambling.
Where B337 fits
For arbitrage, B337 is the finding half: software you run yourself, not a bookmaker, that never takes bets or holds your money. The Terminal is B337's live odds board: racing and sports prices from 40+ bookmakers, with exchange back and lay beside them. Its arbitrage screener runs the book percentage over the sports markets on it and lists those under 100%, with the margin as a share of the total stake.
B337 does not place arbitrage bets automatically. There is no arbitrage strategy in the bot: the screener finds candidates, and placing both legs is yours to do. Terminal Pro adds clicking a price on the board to place that bet in your own account by hand, one leg at a time; it needs that bookmaker account attached to your B337 bot, which runs on your own computer. Terminal View is $25 a month and read-only, Terminal Pro is $300 a month and includes the screeners, and the screeners are a plan of their own that Terminal View does not include: see pricing. Bets placed through B337, a click on the board included, use credits, a per-bet usage charge on top of the plan price.
See the arbitrage screener's rows
A free account shows the live count on each screener. The rows come with Terminal Pro, Full Automation or the Screeners plan. The lay, arbitrage, dutching and racing promo calculators stay free, with no account needed.
- Each row pairs opposing prices at different bookmakers that, on paper, return more than the total staked
- Arbitrage % is the margin as a share of the total stake
- The +EV and middles screeners beside it
Betting involves risk. Bookmakers can restrict or close accounts and void bets, automation can fail, prices move, and a positive expected value (+EV) bet can still lose. Promotions carry each bookmaker's own terms. There is no guarantee of profit. For free and confidential support call 1800 858 858 or visit gamblinghelponline.org.au. See responsible gambling for limits and support.
Common questions
Is arbitrage betting worth it in Australia?
It depends on the margins you can get on, how long your accounts last and how much time it takes. In the worked example $200.00 clears about $5.70 if both legs stand, so one mis-staked or refused leg can cost more than several arbs make: the even split loses $20.00. Treat a screener's margin as the best case: the hard parts are getting both legs accepted and keeping accounts open.
Will a bookmaker close my account for arbing?
It can. Bookmakers in Australia decide under their own terms who they take bets from and for how much, within the minimum bet limits some racing bodies set on racing. No software changes that.
How is arbitrage different from +EV betting?
An arb covers every outcome, so on paper it returns the same amount whichever way the event goes, as long as both legs are accepted at the prices shown and both bookmakers settle it the same way. A +EV bet backs one outcome at a price above what it is worth, and can lose. Arbs need two bookmakers out of line with each other; +EV needs one bookmaker out of line with the market.
Can arbitrage be automated?
Parts of it: finding candidates is a data job, which is what a screener does, but placing both legs means two bets landing close together, at the prices you saw, in accounts that both work. B337 does not place arbitrage bets automatically, and how betting bots work covers what placement software does.
Do I pay tax on arbitrage profits?
For most people betting winnings are not taxed in Australia and losses are not deductible, unless the betting is carried on as a business. The ATO's ruling IT 2655 weighs whether betting is systematic, organised and businesslike, how big it is, and whether it is done mainly for profit. B337 does not give tax advice, so ask the ATO or a registered tax agent about your own case.
Keep reading
Start with a free account
A free account opens a limited view of the Terminal with live odds, and the arbitrage screener's live count with the rows locked. The rows come with Terminal Pro, Full Automation or the Screeners plan; Terminal View adds the full board but not the screeners.