Guide · 9 min read
Arbitrage betting risks: what can go wrong, how likely it is and what it costs
Sure bets are called sure because the maths covers every result. In practice the maths only holds under conditions bookmakers don't always meet. This guide lists everything that can go wrong, how often it tends to happen, what it costs in euros and how to keep each risk small.
Updated 22 October 2026
Contents
In short: covered on paper, not risk-free in practice
With a sure bet you back every outcome of one event at different bookmakers, at prices where each outcome pays a little more than your total stake. How that works is explained in sure betting explained. The result of the match then no longer matters. But that only holds under three conditions:
- Every bet is accepted at the odds shown, for the full stake.
- Every bet stands and is settled under the same rules.
- The bookmaker pays your money out.
If any of these fails, the sure bet turns into an ordinary bet, and one of sure-bet size. That is the core of every risk on this page: the margin is usually 1 to 2% of the stake, but the possible loss from a mistake is up to 100% of one side. That's why we never call sure bets safe or risk-free.
The price moves before your second bet
Likelihood: high. Cost: usually small. This is the most common problem of all. Seconds to minutes pass between your first and second bet, and that is exactly when the bookmaker with the outlying price tends to adjust it. The price that is out of line with the market is the one most likely to be corrected.
Tennis, €500 total stake. Bookmaker A offers 2.08 on Player 1, Bookmaker B 2.00 on Player 2. S = 1/2.08 + 1/2.00 = 0.98077, about a 1.96% return. The plan: €245.10 at A and €254.90 at B, each outcome paying about €509.80.
You bet at A. Before you get to B, its price drops to 1.93. For the same payout you now need 245.10 × 2.08 ÷ 1.93 = €264.15. Total stake €509.25, payout €509.81: still about +€0.56. If the price drops to 1.85, you need €275.57, stake €520.67 in total and are about €10.86 down whatever the result.
The damage stays small as long as you cover straight away. It gets expensive if you leave the open side and hope for a better price. Then you hold an ordinary single bet with full risk.
Voids and palpable errors
Likelihood: occasional. Cost: large. Almost all bookmakers reserve the right in their terms to void bets at obviously wrong prices, or to resettle them at the correct price. Your stake comes back, but the other side of your sure bet keeps running. Sure bets with a conspicuously high margin are hit most often: a margin of 8% or more is usually an error, not a lucky find.
The same sure bet as above: €245.10 at A at 2.08, €254.90 at B at 2.00. Planned profit: about €9.80. Then A voids the bet and refunds the €245.10.
Without cover you now have €254.90 open on Player 2: +€254.90 if she wins, −€254.90 if she loses. Your exposure is about 26 times the planned profit.
With cover before the match: Bookmaker C offers Player 1 at 1.95. Covering stake = 254.90 × 2.00 ÷ 1.95 = €261.44. If Player 2 wins you get €509.80 on €516.34 staked; if Player 1 wins, €509.81. Either way you are about €6.54 down.
Void after the match: you can no longer cover. If Player 2 lost, the €254.90 is gone.
What to do after a void, and when a bookmaker may and may not cancel a bet, is covered in voided bets and palpable errors.
Different settlement rules
Likelihood: rare to occasional. Cost: medium to large. Two bookmakers can settle the same match differently. In the worst case none of your bets wins. Typical cases:
- Tennis retirements. Some bookmakers settle the bet if at least one set was completed, others void it on any retirement, others let it stand once the match has started. If a player retires, one side can be voided and the other lost.
- Overtime and penalties. In football the market is usually regulation time including stoppage time; in ice hockey and basketball, often including overtime. If one bet slip says "incl. overtime" and the other doesn't, it isn't a sure bet.
- Abandoned or postponed matches. Deadlines differ: some still settle a bet if the match is replayed within 48 hours, others void it straight away.
- Player bets. If a player doesn't start, some bookmakers void the bet and others settle it as lost.
The rules are in each bookmaker's betting rules, usually split by sport. Read them for the sports you bet on before your first sure bet there. The differences are laid out in arbitrage betting by sport.
Betting fees and deductions
Likelihood: certain at some bookmakers. Cost: small, but on every bet. In Austria a 5% betting fee on the stake has applied since 1 April 2025. The bookmaker owes it; most absorb it, but some deduct it from the stake or the winnings. Because a sure bet's margin is usually only 1 to 2%, such a deduction almost always makes it a losing proposition at that bookmaker. A full worked example is in our guide to Austria's betting tax, and you can test your own prices in the arbitrage calculator.
Deposit and withdrawal fees and currency conversion work the same way. Each is small; over a month they can eat a noticeable part of your margin.
Limits and account closures
Likelihood: high, almost certain over time. Cost: small directly, large for your results. Bookmakers restrict accounts that win regularly. For a single sure bet this is dangerous mainly when a bet is only partly accepted: you want to stake €254.90 and the bookmaker takes €80. The other side no longer fits, and you have to place the rest elsewhere, often at a worse price.
Over time, limits are the main reason sure betting doesn't scale indefinitely: at some bookmakers after weeks, at most within months. More in how bookmakers limit accounts.
Tied-up money and withdrawal problems
Likelihood: occasional. Cost: from annoying to large. Your money is spread across several betting accounts. That brings three risks:
- Delayed withdrawals. Before the first withdrawal, bookmakers ask for identity checks (ID, sometimes proof of address or payment). That can take days, and the money is blocked in the meantime.
- Refused withdrawals. Rare at reputable, licensed bookmakers; a real risk at bookmakers without a licence in your country or the EU. That is often exactly where the "best" prices show up. ArbVantage doesn't hide such bookmakers; it shows a neutral licence flag so you can decide for yourself.
- A bookmaker going bust. Customer balances at bookmakers are not protected like bank deposits. Don't keep more in any account than you actually need there.
Typing mistakes
Likelihood: rare, but it happens to everyone eventually. Cost: large. A mistyped stake (€25.49 instead of €254.90), the wrong side clicked, "over" instead of "under", the wrong line (handicap −1 instead of −1.5) or the wrong match with the same name. Each of these turns a sure bet into an open bet. Read the bet slip back before you confirm.
Risk matrix: likelihood × cost
The ratings are an estimate from experience with pre-match sure bets on common markets, not statistics. They help you put your attention where it matters most.
| Risk | How often | Cost per case | Main countermeasure |
|---|---|---|---|
| Price moves before the second bet | often | small (part of the margin up to about 2%) | place the outlying price first, cover straight away |
| Bet only partly accepted | occasional, more often with limits | small to medium | check the accepted stake before the second bet |
| Void for a palpable error | occasional | large (up to the whole open side) | avoid margins above about 8%, keep a reserve to cover |
| Different settlement rules | rare | medium to large | compare rules per sport beforehand |
| Betting fee passed on | always, at some bookmakers | small per bet, adds up | calculate with the odds after the deduction |
| Typing mistake | rare | large | read the bet slip back before confirming |
| Limit or account closure | almost certain over time | lowers future results | plan for it, spread your money |
| Withdrawal delayed or refused | rare (licensed) to occasional (unlicensed) | medium to total | check the licence, verify early, keep balances small |
The frequent risks cost little; the rare ones cost a lot. A single void that goes badly can cost more than ten good sure bets earn. That is why discipline matters most with the rare risks.
How to keep each risk small
- Place the bet whose price is most likely to drop first, usually the one out of line with the market. The stable side comes second.
- After the first bet, check the accepted stake and price; only then place the second.
- Compare both bet slips: same match, same market, same line, same playing time.
- Be suspicious of high margins. Real pre-match sure bets are usually 1 to 2%.
- Know your bookmakers' rules on retirements, overtime and abandoned matches.
- Price in deductions, especially a passed-on betting fee.
- Keep a reserve at a third bookmaker so you can cover quickly after a void.
- Verify every account right after opening it, and withdraw surpluses regularly.
- Start small. A single side should never be bigger than an amount you can afford to lose.
- Keep records, so you can see which margin actually arrives and which mistake costs you most.
ArbVantage takes some of this off your hands: the app prices in known betting fees, respects the maximum stakes you enter, and its "Odds changed or bet rejected?" tool works out the best way out when a price drops or a bet is rejected. The decision on every bet stays with you. If betting starts to feel like pressure, our responsible gambling page lists free help.
Frequently asked questions
Can you lose money with sure bets?
Yes. A sure bet is only covered if every bet is accepted at the odds shown and stands. If a price drops, a bet is voided or two bookmakers settle differently, any single sure bet, and even a whole month, can end in a loss.
What is the biggest risk with sure bets?
The most common is a price moving before the second bet, which usually costs little. The most expensive is one side being voided, especially after the match: you are then left with an uncovered single bet for the full amount.
Is arbitrage betting gambling?
Legally, Austria's Supreme Court (OGH) has held that sports betting is not gambling under the federal Gambling Act; it is regulated by the betting laws of the federal states. In Slovakia, sports betting is a regulated form of gambling under the Gambling Act. Either way it is betting with real money and a real risk of loss, and responsible gambling applies just the same.
How much should I stake per sure bet at most?
Enough that you could cope with losing one side if it is voided and the other loses. At the start that means more like €50 to €100 per side. Later, a rule of thumb is to stake at most about a sixth of your capital per sure bet.
Sources
- Unternehmensserviceportal (USP): Wettgebührenabrechnung (in German)
- RIS: Gebührengesetz 1957, § 33 TP 17 (bets) (in German)
- WKO: Supreme Court ruling, sports betting is not gambling under the GSpG (in German)
- Slov-Lex: Act No. 30/2019 Coll. on gambling (in Slovak)
- Malta Gaming Authority: complaints about a licensee
As of October 2026. Bookmakers' rules, odds and offers change; their current terms and betting rules always apply.
Betting involves risk, even with sure bets: prices move, bets get voided, accounts get limited. Only use money you can do without. Our responsible gambling page lists free help in Austria and Germany.
Information, not betting, legal or tax advice. 18+.