Guide · 8 min read
Arbitrage betting mistakes: 12 errors, sorted by the damage they do
A sure bet only behaves like one when both legs are on the same thing, at the prices you calculated, and both stand. Almost every loss beginners report comes from one of the twelve mistakes below. The first ones can wipe out a month of margin in a single bet.
Updated 22 October 2026
Contents
How this list is sorted
A typical pre-match sure bet earns 1 to 2% of what you stake. On €200 that is €2 to €4. The mistakes below are sorted by how much one occurrence can cost compared with that: the first three can turn a €4 edge into a €200 loss, the last ones cost you slowly. If you are new, read our sure betting guide first; this page assumes you know how stakes are split.
1–3: wrong market, typos and the betting fee
1. Betting the wrong market or the wrong line
Both legs must cover exactly opposite outcomes of the same event. The most expensive mistake is a leg that looks right but isn't: Over 3.5 instead of Over 2.5, a handicap of −1 instead of −1.5, "match winner including overtime" at one bookmaker and "regular time" at the other, the first set instead of the match, or the women's team with the same name.
You want Over 2.5 goals at 2.10 and Under 2.5 at 2.05 with €200 in total: €98.80 and €101.20. Both outcomes pay about €207.47, roughly €7.47 up.
On the first slip you click Over 3.5 at 2.10 by mistake. Now 0–2 goals still pays (Under wins, about +€7.46), 4 or more goals still pays (Over wins, about +€7.48), but exactly 3 goals loses both bets: −€200.
Check five things on both slips before you confirm: event, date and start time, market, line, and period (full time, regular time, set, half). Read the slip, not the button you clicked.
2. Typing the wrong stake or reading the wrong odds
A missing digit or a comma in the wrong place leaves one side almost unhedged. The same goes for reading 2.50 where the slip says 2.05.
Same bet: you type €10.12 instead of €101.20 at 2.05. If the Over wins you are about €98.56 up; if the Under wins you are €88.17 down. That is a coin flip, not a sure bet.
The fix is to top up the short leg before kick-off. If 2.05 is still there, add €91.08 and you are back to the original split. If it has dropped to 1.95, add €95.76: (207.48 − 10.12 × 2.05) ÷ 1.95. You have now staked €204.68 and either outcome pays €207.48, so you keep about €2.80 instead of €7.47.
Copy stakes instead of typing them where you can, and read the confirmed slip before you move on to the second leg.
3. Forgetting a betting fee or tax
In Austria the Wettgebühr has been 5% of the stake since 1 April 2025. The bookmaker owes it, and most absorb it, but some pass it on by cutting the stake, charging it on top or reducing the payout. A passed-on 5% is bigger than a 1–2% edge, so the bet becomes a guaranteed small loss. Our guide to the Austrian betting tax shows the maths; Germany's 5.3% betting tax works similarly. Always calculate with the price after any deduction: payout on the slip divided by what left your balance.
4–6: stale odds, leg order and settlement rules
4. Betting on stale odds
Sure bets often exist because one bookmaker hasn't moved its price yet. By the time you open the slip it may have. If the slip shows a lower price, recalculate before you accept the change. Margins that look unusually large (above about 10%) are rarely real; they usually mean an error that will be voided (see voided bets and palpable errors). Look at how old the price is before you start.
5. Placing the stable leg first
The leg that is most likely to move, be partly accepted or be refused is the out-of-line price at a bookmaker that limits winners. Place that one first. Only when it is confirmed at your price and full stake, place the other leg, which is usually the market price that many bookmakers offer and that will still be there a minute later. Doing it the other way round leaves you holding the easy leg while the hard one disappears.
6. Not comparing settlement rules
Two bookmakers can settle the same match differently. The classic case is a tennis retirement: some settle bets once the first set is complete, others void everything unless the match is finished. Others are a match that is postponed or abandoned, overtime in ice hockey and basketball, and the 90-minute rule in football. If one leg is voided and the other is settled, you are left with a single bet. Our guide to bookmaker limits explains what to read before you deposit.
7–10: money in the wrong place and missing records
7. Keeping all your money at one or two bookmakers
A sure bet needs money at two (sometimes three) bookmakers at the same moment. If your balance is in the wrong place, the opportunity is gone before a deposit lands. Spread your bankroll by how often each bookmaker shows up, and keep a reserve for hedges. Our starting bankroll guide has example splits.
8. Odd-looking stakes
€47.62 next to €52.38 is exact, but it also looks calculated. Round the leg at the bookmaker that is more likely to limit to an ordinary amount like €50 and rescale the other leg to match; the margin barely changes. Nothing prevents limits, but there is no reason to make the bet slip stand out.
9. Not keeping records
Without a log of every bet (date, bookmaker, market, odds, stake, result) you can't tell whether you are actually earning the margin you see, which bookmakers you use most, or what you have where. Records also answer questions from your bank or tax office quickly. Five minutes a day is enough; ArbVantage's Tracking does it for bets you place from the app.
10. Treating bonus money like cash
A free bet usually doesn't return its stake, so a €20 free bet at 3.00 pays €40, not €60. Bonus funds often come with wagering requirements, minimum odds and excluded markets, and voided bets may not count. If you calculate a cover bet as if it were cash, both sides won't pay the same. Our free bets guide shows the correct formula.
11–12: stakes that are too big and chasing losses
11. Starting with large stakes
The first weeks are when you make most of the mistakes above. A €1,000 stake turns a wrong line into a €1,000 loss. Start small enough that a single mistake doesn't hurt, learn the routine, and scale up when your records show the routine is clean. Large stakes from day one are also one of the signals that shorten an account's life.
12. Trying to win back a loss
After a void or a mistake, it is tempting to take a bigger or riskier bet to get the money back. That turns an arbitrage routine into gambling. Accept the loss, write down what went wrong and continue with your normal stakes. If you notice you are betting more than planned or hiding it from others, stop and look at our responsible gambling page.
Checklist to print
- Margin plausible (usually 1–5%)? Price fresh?
- Same event, date, market, line and period on both slips?
- Settlement rules compatible (retirement, overtime, abandonment)?
- Betting fee or tax deducted? Use the price after the deduction.
- Money already on both accounts, plus a reserve for a hedge?
- Stakes copied, not typed? Leg at the bookmaker that limits rounded?
- Out-of-line leg placed first, full stake confirmed at your price?
- Second leg placed, both slips checked again, screenshots taken?
- Both bets logged?
Every point on the list is something the software can't do for you: you place every bet and you check every slip. What ArbVantage does is the arithmetic, the deduction of known fees, rounding and a recalculation when a price changes or a bet is refused.
Frequently asked questions
Which leg of a sure bet should I place first?
Place the leg most likely to change first: usually the out-of-line price at a bookmaker that limits winners. Only when it is confirmed at your price and full stake, place the other leg, which is usually a market price that will still be there a minute later.
What should I do after a typo in my stake?
Top up or cover the short leg before the event starts. Work out the extra stake from the payout you need, using the price that is available now. You keep a smaller margin or take a small known loss instead of an open bet.
How do I avoid betting the wrong line?
Read the confirmed bet slip, not the button you clicked, and compare five things on both slips: event, date and start time, market, line and period. Be suspicious of any margin that looks unusually large, because it often means the lines don't match.
Sources
- Unternehmensserviceportal (USP): Wettgebührenabrechnung (in German)
- RIS: Gebührengesetz 1957, § 33 TP 17 (bets) (in German)
- ÚRHH: legal online gambling and betting websites in Slovakia (in Slovak)
As of October 2026, checked against the linked sources. Not legal, tax or betting advice.
Betting involves risk, even with sure bets: prices move, bets get voided and accounts get limited. Only use money you can do without. Our responsible gambling page lists free help.
Not betting advice. 18+. Betting involves risk. See our disclaimer.