Cross-exchange arbitrage means backing a runner on one exchange and laying it on another (typically Betfair and Smarkets) when their prices differ enough to lock a profit across all outcomes. The gaps are usually tiny and exist largely because Smarkets charges ~2% commission vs Betfair's 2–5%. Profits are small, execution risk is real (prices move before both legs fill), and it needs two funded accounts and fast hands.
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This is a sub of our arbitrage and value pillar, and it covers the most technically demanding form of exchange arbitrage: arbing one exchange against another. If you're new to the concept, start with how arbitrage works and our note on whether arbitrage is legal on Betfair (it is). This piece assumes you understand backing and laying and want the cross-exchange specifics.
What cross-exchange arbitrage is
Both Betfair and Smarkets are betting exchanges — peer-to-peer marketplaces where you back and lay against other users rather than a bookmaker. Because they're separate pools of money with separate users, the same runner can momentarily trade at slightly different prices on each. Cross-exchange arbitrage exploits that gap: you back the runner where the price is higher and lay it where the price is lower, sizing the stakes so that whatever the result, your back winnings on one platform cover your lay liability on the other and leave a small profit. Unlike back-versus-bookmaker arbitrage, both legs are on exchanges, so there's no bookmaker to restrict you — a real structural advantage for anyone who's been gubbed.
Why the gaps exist (and why commission is the key)
The naive view is that two efficient exchanges should always show the same price, so any gap is free money. The reality is more subtle, and commission is the centre of it. Smarkets charges a flat ~2% commission on net winnings, while Betfair charges 2–5% depending on your market base rate. That commission difference means the effective price you receive after costs differs between the two even when the displayed prices look similar — and it's the after-commission price that determines whether an arb actually exists. A gap that looks like an arb on displayed odds can vanish once you apply each platform's commission; conversely, Smarkets' lower commission sometimes makes its effective price better even when its displayed price is marginally worse.
The other source of gaps is simply liquidity timing: Betfair is far deeper than Smarkets on most markets, so a price moves on Betfair first and Smarkets lags for a few seconds. That lag is the window an arb lives in — and it's exactly why execution is so hard. By the time you've clicked both legs, the lagging exchange may have caught up.
How to execute it
The mechanics are simple to state and hard to do under time pressure:
- Fund both accounts. You need money sitting ready on Betfair and Smarkets simultaneously — you can't move funds fast enough to react.
- Find the gap. Compare the back price on one exchange with the lay price on the other for the same runner, after commission. An arb exists when (back odds, net) > (lay odds, net) by enough to clear both commissions.
- Calculate the lay stake. Use the standard lay-stake formula (or a calculator) so the position is balanced across outcomes. Our hedging calculator handles the same maths.
- Fire both legs fast. Place the back and the lay as close to simultaneously as possible. This is the whole game — the gap closes in seconds.
Most people who do this seriously use value/arb software or two screens side by side, because manually finding and executing before the gap closes is genuinely difficult. Compared to single-exchange value betting, the operational demands are an order of magnitude higher.
The market: a second-round ATP match, the favourite priced around 1.50. Tennis is good for this — two-runner markets, clean prices, and Betfair moves first on a momentum shift while Smarkets lags.
The gap: after a break of serve, Betfair's back price on the favourite spiked to 1.62 for a moment while Smarkets still showed a lay available at 1.57. After commission (Betfair 5%, Smarkets 2%) that was a genuine, if thin, arb.
Execution: I backed £200 at 1.62 on Betfair and laid the balancing stake (£206 at 1.57) on Smarkets. Both filled within about two seconds — the Betfair price was already collapsing back as I clicked.
The result: locked profit of roughly £5.10 across both outcomes after both commissions — on £200 turnover, about a 2.5% return on the stake, result-independent.
The lesson: it worked, and £5 risk-free is £5 risk-free — but I got the second leg filled with maybe a second to spare. On the previous attempt that morning the Smarkets lay vanished before my click landed, leaving me with an unhedged £200 tennis position I had to scramble out of for a small loss. That is the real risk of cross-exchange arbitrage: not that the maths is wrong, but that one leg fills and the other doesn't, turning a “risk-free” arb into a naked bet.
The risks the calculators hide
Arb calculators show you the clean locked profit and none of the ways it goes wrong. The dominant risk is execution / one-legged exposure: you fill the back leg, the lay price moves before you fill it, and now you're holding an open position the arb was supposed to neutralise. In a fast-moving market that single-leg slippage can cost more than several successful arbs made. Secondary risks include price movement between clicks, minimum stake and liquidity limits on the thinner exchange (Smarkets is shallower, so you may not get your full lay matched), and the Premium Charge on Betfair if you become a high-volume winner. None of these appear in the calculator's tidy profit figure, and all of them are why the real-world return is a fraction of the theoretical one.
Is it worth it?
For most traders, honestly, no — or only as a marginal supplement. The gaps are small, fleeting, and capped by Smarkets' thinner liquidity, so the absolute profit per arb is usually a few pounds, and the time and capital tied up across two funded accounts is significant. Where it earns its place is for traders who already run software scanning both exchanges and can execute near-instantly, treating cross-exchange arbs as a low-variance trickle alongside their main edge. It's also genuinely useful for anyone restricted by bookmakers, since both legs are on exchanges that don't gub winners. But as a standalone “guaranteed profit” strategy, the execution risk and thin margins make it far less attractive than the calculators imply. The broader arbitrage and value pillar sets out where the better risk-adjusted edges actually are.
Betdaq and the wider exchange landscape
Betfair and Smarkets aren't the only exchanges, and the wider landscape matters because every additional venue is another potential pricing gap — and another set of execution headaches. Betdaq is the third significant exchange; it's smaller and thinner than Betfair, with commission that's competed down over the years, and our Betfair vs Betdaq liquidity comparison covers where it stands. In principle a three-way arb across Betfair, Smarkets and Betdaq is possible; in practice the thinner books on the smaller two cap your stakes and widen the execution risk to the point where it's rarely worth the operational complexity for most traders.
The general rule across the landscape is that liquidity concentrates on Betfair, so Betfair's price is usually the “true” one and the smaller exchanges lag it. That makes the smaller venue almost always the leg that fails to fill — you can hit Betfair instantly but the Smarkets or Betdaq side might not be there in the size you need. Understanding this asymmetry is what separates traders who profit from cross-exchange gaps from those who repeatedly end up one-legged on the thin venue. If you're going to do this, do the uncertain leg (the thin exchange) first and the certain leg (Betfair) second — the opposite of most people's instinct, and the order that minimises naked exposure.
Building a cross-exchange workflow
If you've decided cross-exchange arbitrage earns a place in your trading, the difference between profit and frustration is workflow. The traders who make it pay treat it as an operational discipline, not a treasure hunt. The core components are a price feed across both exchanges (software or two screens), pre-funded accounts with enough on each to react without transfers, a calculator or tool that instantly sizes the lay leg after commission, and a fixed execution order that fills the thin leg first. None of this is optional — the gaps close in seconds, so anything you have to think about in the moment is a gap you'll miss.
Set realistic expectations for what the workflow produces. Even run well, cross-exchange arbing is a low-variance trickle, not a torrent — a few pounds per successful arb, several per session on a busy day, with the occasional small loss when a leg slips. It suits a patient, systematic temperament and pairs best as a supplement to a primary edge like value betting or scalping, using scanning tools that surface the gaps automatically. Done as a careful sideline by someone already comfortable on both exchanges, it adds a steady drip of low-risk profit; chased manually as a main strategy, it'll cost you more in slippage and screen time than it returns. The arbitrage and value pillar sets it in the context of better-paying edges.
Records, tax and the long game
If cross-exchange arbing becomes a regular part of your trading, the unglamorous admin matters more than people expect. Keep detailed records of every arb — both legs, both prices, stakes, commissions and net result — because reconciling profit across two exchanges is genuinely fiddly, and you can't manage what you don't measure. Good records also tell you the truth about whether the strategy is actually paying after the losses from slipped legs, which the optimistic mental arithmetic tends to forget. More than one trader has believed they were grinding out arbs profitably until they totted up the one-legged losses and found they were roughly break-even for a lot of screen time.
On tax, UK betting and trading winnings are generally not taxed for individuals, but rules vary by jurisdiction and circumstance, and this isn't tax advice — if you're trading at scale, take proper professional guidance for your situation. The broader long-game point is that cross-exchange arbitrage is a capacity-limited, low-ceiling activity: the gaps are small, the liquidity caps your stakes, and it doesn't scale into serious income the way a genuine edge can. Treat it as a steady low-variance supplement that pairs with a main strategy, keep meticulous records, and don't let the “risk-free” framing lull you into ignoring the execution losses that are very real. The arbitrage and value pillar and the finding value guide point toward the higher-ceiling edges worth more of your attention.
Better uses of the same effort
It's worth asking what else you could do with the capital, software and attention that cross-exchange arbing demands, because the opportunity cost is real. The same two funded accounts and scanning setup can power value betting, which has a higher ceiling because it isn't capped by the thin liquidity of the smaller exchange. The same fast-execution skills transfer directly to pre-race scalping on Betfair alone, where the liquidity is deeper and you're not exposed to one-legged risk across two platforms. And the same record-keeping discipline applied to a single coherent strategy compounds better than it does spread thinly across marginal arbs.
None of that means cross-exchange arbitrage is worthless — for the right systematic trader it's a steady, low-variance supplement, and it's genuinely useful for anyone restricted by bookmakers who needs exchange-only options. But I'd rarely recommend it as a primary focus, because the effort-to-reward ratio favours strategies that aren't capped by a thin counterparty pool. Know it, run it as a sideline if it suits your temperament, but build your main edge somewhere with more headroom. The arbitrage and value pillar maps where that headroom actually is.
The verdict
Cross-exchange arbitrage between Betfair and Smarkets is real, legal and result-independent in theory — but in practice it's a thin, fast, execution-heavy grind. The gaps exist largely because of the commission difference (Smarkets ~2% vs Betfair 2–5%) and Betfair's liquidity leading Smarkets by seconds. The dominant risk isn't bad maths but one leg filling without the other, and the profits are small and capped by Smarkets' shallower pool. Worthwhile as a software-assisted supplement for restricted bettors or systematic arbers; not worthwhile as a manual get-rich scheme. Build from how arbitrage works, the arbitrage pillar, and the Betfair vs Smarkets commission comparison.
“Risk-free” cross-exchange arbitrage carries real execution risk — if one leg fills and the other doesn't, you hold an unhedged position that can lose more than several arbs make. Profits are small, capped by liquidity, and reduced by commission and the Premium Charge. Past results don't guarantee future returns. 18+ only; help at BeGambleAware.org.
Understand both exchanges' commission before you chase the gaps between them.
Betfair vs Smarkets Open Betfair Account →FAQ
Is cross-exchange arbitrage between Betfair and Smarkets legal?
Yes. Arbitrage is entirely legal, and because both legs are on exchanges rather than bookmakers, there's no bookmaker to restrict or gub you for doing it. The practical constraints are execution difficulty and, for high-volume Betfair winners, the Premium Charge — not legality.
Why do prices differ between Betfair and Smarkets?
Two reasons. First, commission differs — Smarkets charges about 2% versus Betfair's 2–5% — so the effective after-cost price differs even when displayed odds look similar. Second, Betfair is far more liquid, so its price moves first and Smarkets lags by a few seconds, which is the window an arb briefly lives in.
What's the biggest risk in cross-exchange arbitrage?
One-legged exposure. You fill the back leg, but the lay price on the other exchange moves before you fill it, leaving you holding an open, unhedged position the arb was meant to neutralise. In a fast market that slippage can cost more than several successful arbs earned — the maths is sound, the execution is the danger.
Is cross-exchange arbitrage worth doing?
For most people, only marginally. The gaps are small and fleeting, Smarkets' thinner liquidity caps your stake, and two funded accounts tie up capital. It earns its place mainly for traders running scanning software who can execute instantly, and for bettors restricted by bookmakers — but not as a standalone get-rich strategy.
Related reading
Start with how arbitrage works and the arbitrage and value pillar, compare the venues in Betfair vs Smarkets and Betfair vs Betdaq, and check the legality note in is arbitrage legal?