Football arbitrage betting in the UK: how it works and what goes wrong

What a football arb is

Every price implies a probability: one divided by the decimal odds. A bookmaker’s prices on a market add up to more than 100% — the excess is its margin, the overround. An arbitrage exists when you can assemble a full set of outcomes from different firms and the implied probabilities add up to less than 100%. The shortfall is your margin, and it is paid whichever outcome happens, because you hold every outcome.

In football that is most often a two-way market — over/under goals, a player’s shots line, both teams to score — where one firm is slow to move or has priced a side generously. Three-way arbs on the match result exist but need three prices to line up and are rarer.

The arithmetic, worked

Suppose one firm offers Over 2.5 goals at 2.10 and another offers Under 2.5 at 2.00.

Two rules fall out of the table. The stake on each side is proportional to its implied probability, so the shorter price takes the larger stake. And the margin is small: real football arbs are typically one to a few per cent of the total staked, which is why the risks in the next section matter more than the maths.

When one leg is on an exchange, commission is charged on the net winnings of that leg, which reduces the margin and shifts the split. The scanner on this site shows margins after commission for that reason.

Where arbs come from, and why they close

Firms move at different speeds. When team news breaks or the sharp market shifts, a recreational book can be a few minutes behind, and for those minutes the old price and the new price at another firm may combine into an arb. Boosted prices, opening lines on player markets, and low-liquidity exchange markets produce them too. All of these close as soon as the slower firm catches up — often within minutes, sometimes within the time it takes to place the second leg.

What goes wrong

The arithmetic is only true if both legs are placed at the prices shown, for the stakes shown, and settled by the same rules. Each of those can fail.

• The price moves between legs. You place leg one; leg two has shortened before you reach it. You now hold a one-sided bet at a price you did not choose. The usual practice is to place the leg most likely to move first — the outlier, the boost, the thin market — and the stable leg second, but nothing removes the gap entirely.
• The stake is refused or cut. Bookmakers limit stakes, and an accepted leg one with a leg two accepted for half the stake is not an arb. Check what each firm will take before placing either.
• The rules do not match. Two firms can settle the “same” bet differently: what counts as a shot on target, whether a player who does not start is void or lost, how extra time or abandonment is treated, which data provider settles the stat. A mismatch turns a covered market into two separate bets. The scanner pairs legs whose settlement rules match, and the page says to verify both before staking.
• Palpable errors. A firm that has priced a market obviously wrong can void bets under its terms. The other leg stands.
• Account restrictions. Nothing in UK law stops you backing both sides at two firms, but most bookmakers’ terms let them limit stakes or close accounts that arb, and they do. Over any length of time this is the largest cost of arbitrage, and it is why the record on this site is a record of what existed, not a promise that you could have taken it.

How the Per90 scanner works

The scanner rechecks live prices across the UK books and exchanges it captures every 5 minutes and shows the combinations whose margin clears the board’s minimum after commission. For each one you see both legs with the firm and the price, how old each price is, and the stake split for a bankroll you enter — the arithmetic above, done for you. The minimum margin is stated on the board itself.

Every arb the board publishes goes on a permanent record with the margin at the moment it was called, the widest it got, and how long it stood. Arbs that were voided because the match did not start stay on the record, marked as such. Nothing is removed, so the record can be read as a measure of how often these windows open and how long they last — which is the honest answer to whether arbitrage is worth your time.

Using one

1. Open both prices at both firms and confirm they are still as shown.
2. Confirm the settlement rules match for the exact market and line.
3. Check the stake each firm will accept.
4. Place the leg most likely to move first, then the other immediately.
5. If leg two is refused or cut, decide about the exposure you now hold before anything else.

Open the arbitrage scanner → for what is open now and the record of everything that has been.