Money back if one leg fails: how multi insurance works and what it is worth

Money back if one leg fails is a multi promotion that refunds your stake, often as a bonus bet up to a cap, when every leg of your multi wins except one. It pays on a near miss, so its value turns on one number: the chance that exactly one leg fails, which you can work out from the leg prices once the bookmaker's margin is removed.

With illustrative prices, a $30 four-leg multi at $6.06 misses by exactly one leg 35.19% of the time. On its own the multi is worth -$5.65 on average. A refund paid as a bonus bet, valued at 75 cents in the dollar, adds $7.92 and lifts it to about +$2.27, while the ticket still loses its stake with nothing back 51.42% of the time.

How multi insurance works

If exactly one leg of a qualifying multi fails while the rest win, the bookmaker refunds your stake up to a maximum. The names vary (multi insurance, one-leg refund, multi saver), so read what the terms pay rather than the label:

The cap is the most the refund pays, such as an illustrative $30 per multi; stake more and the excess is a plain multi with no cover. A bonus bet refund has its own expiry and terms, and under the National Consumer Protection Framework for online wagering what it wins must be withdrawable with no turnover requirement.

In NSW, Liquor & Gaming NSW's guideline GL4015 names refund offers, paid in cash or as a bonus bet, among the inducements it treats as prohibited when advertised to the world at large. Account holders who have agreed to receive offers can still be sent some of them directly (checked October 2026). Betting promotions in Australia maps the other offer types.

The legs below come from different games, so their chances can be treated as independent. A same game multi's legs move together, which changes the sum, and same game multi promotions works through that case.

The chance exactly one leg fails, from the leg prices

Work from fair chances, not the bookmaker's prices, because each price carries a margin. For a two-way leg, the proportional method scales both sides' implied chances to 100%: fair chance = (1 / your price) / (1 / your price + 1 / the other price). Other methods take more margin off the longer price, which would raise each of these chances, as every leg below is the shorter price.

1. All four win: 0.63415 x 0.54974 x 0.58673 x 0.65476 = 0.13393, or 13.39%.
2. The chance that one leg alone fails is the all-win chance x (1 - its chance) / its chance, and (1 - chance) / chance is the same as fair price - 1. So exactly one fails = 0.13393 x (0.57692 + 0.81905 + 0.70435 + 0.52727) = 0.13393 x 2.62759 = 35.19%, the sum of the last column.
3. Two or more fail: 100% - 13.39% - 35.19% = 51.42%.

This multi misses by exactly one leg about 2.6 times as often as it wins. Reading the bookmaker's prices as chances, margin left in, gives 1 / 6.0604 = 16.50% for all four winning and 0.16501 x (0.50 + 0.72 + 0.62 + 0.45) = 37.79% for exactly one failing. That overstates the refund and hides the margin the multi carries.

Worked: a four-leg multi with the refund as a bonus bet

The legs multiply to 1.50 x 1.72 x 1.62 x 1.45 = $6.0604, so a $30 multi returns $181.81 if all four win. You stake $30, the most that illustrative cap covers. A bonus bet is worth less than cash: valued at 75 cents in the dollar, what one keeps on average when used at a fair $4.00 (1 - 1 / 4.00 = 0.75), the $30 refund is worth $22.50.

The refund more than covers this multi's margin, but only on average: 13.39% of the time the ticket pays $181.81, 35.19% of the time it returns a $30 bonus bet, and 51.42% of the time it returns nothing. Every dollar above the cap is a plain multi returning about 81 cents, and the bonus bet still has to win: used at a fair $4.00 it wins one time in four. To weigh this offer against a boost or a cash refund elsewhere, run each through valuing a betting promotion.

Why more legs is not always better

More legs mean a longer price, but three things work against a one-leg refund as you add them:

1. Each leg's margin multiplies through the multi, so the multi alone loses more per dollar with every leg. Multis vs singles shows the compounding.
2. The chance that exactly one leg fails rises at first, then falls. With legs of equal chance, adding a leg raises it only while the legs you already have number fewer than 1 / (fair price - 1). For legs at a fair $1.50 that is 1 / 0.50 = 2, so two legs and three legs share the peak of 44.44%, and every leg after that lowers it.
3. The refund is your stake, capped, however long the price, so it does not grow with the legs.

For three legs, the multi alone = $30 x (0.96 x 0.96 x 0.96 - 1) = $30 x (0.8847 - 1) = -$3.46. Exactly one fails = 3 x (2/3 x 2/3) x 1/3 = 44.44%, and the refund is worth $30 x 0.75 x 44.44% = $10.00. Each extra leg adds one more 0.96 to the first product, and in the second it adds one more 2/3 and raises the leading 3 by one.

Of the lengths in the table, three legs are worth the most, and six are worth less than nothing on average even though the multi is priced at $8.92. Two legs would be worth more again, +$7.65, if an offer took a two-leg multi, so a minimum-legs term that forces extra legs costs value. The multi bet calculator works out a multi's price and return from its legs.

Terms on minimum legs and odds

The bookmaker decides whether your multi qualifies, and these terms move the value most:

• Minimum legs, such as three or four or more: a forced extra leg can cost more than it adds.
• Minimum odds for each leg, the whole multi, or both. A floor on each leg can rule out the short legs that make exactly one failure most likely. With equal legs, that chance peaks at a fair price of legs / (legs - 1): about $1.33 a leg for four legs and $1.25 for five.
• The maximum refund, which caps the stake the offer covers.
• Eligible sports, markets and bet types, such as whether racing legs count and whether same game multis need a separate offer.
• Void and abandoned legs. Where a void leg is removed and the multi paid on the legs left, the ticket can fall below the minimum legs or odds, and the terms say whether the refund survives.
• For bookmakers authorised in NSW, clause 5.1.9(c) of the Bookmaker Declared Betting Events Betting Rules covers a leg still to run that is abandoned, or postponed and not scheduled within 3 calendar days of its original date. If the legs already decided have won, the multi is paid at their combined price, unless the bookmaker and customer agreed otherwise when the bet was made.
• Dead heats: a leg that dead-heats can settle at a reduced return, neither a clean win nor a loss, and the terms say how the refund treats it.
• Funding, opt-in and the refund's form: whether a multi placed with a bonus bet qualifies, whether you must opt in first, and how long a bonus bet refund lasts.

Mistakes that cost money with multi insurance

With the worked examples' illustrative prices:

Pricing each leg on B337's Terminal

A multi goes on at one bookmaker and its legs multiply, so a few cents more on each of that bookmaker's legs compound into the payout and lift the multi's average. The refund is your stake, so a better price leaves its value unchanged. To see where that bookmaker's leg prices sit against the market, B337's Terminal lines up prices from 40+ bookmakers across racing and sports, with the best available price picked out. Its sports columns cover head to head, line and total markets.

Prices refresh on a repeating cycle rather than with every movement, so a leg can move before you place it; confirm each one in your bookmaker account. A free account opens a limited view of the Terminal with live odds. The EV overlays, which compare each price with an estimated fair price, start with Terminal View, as the B337 plans page sets out.

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