Bet builder

With an ordinary accumulator, the bookmaker multiplies the decimal odds of each leg, because results in different games are treated as independent. A bet builder starts from the same idea and then adjusts for correlation: the degree to which one selection makes another more or less likely.

A worked example

Say the home side is 4/5 to win, which is 1.80 in decimal and an implied probability of about 55.6%, and over 2.5 goals is 10/11, which is 1.91 or about 52.4%. Multiply them and you get roughly 3.44, the price you would expect if the two legs had nothing to do with each other. They do, though, since a team that is winning comfortably has usually scored goals to get there, so the real chance of both landing is higher than 55.6% times 52.4%. The builder will therefore quote you something shorter than 3.44, and how much shorter depends on each operator’s own pricing model rather than any published formula.

Margin sits underneath all of this. If that same match is 4/5 home, 11/4 draw and 10/3 away, the implied probabilities add up to about 105.3%, an overround of roughly 5.3% on the result market alone. Every leg you add carries its own margin, and in a builder those margins compound into a single figure you cannot see broken out on the slip.

So the longer price on a five-leg builder is not a gift.

This is where practice varies most between operators, and there is no single standard to fall back on. BoyleSports, for instance, states in its rules that if any market within a Bet Builder is void or pushed, the entire bet is void, so a goalscorer who never comes on voids the lot regardless of how the other legs went.

Other firms take the opposite route and keep the surviving legs alive at a recalculated price. Because those legs are correlated, the bookmaker cannot simply strip out the void selection at 1.00 the way it would in a standard acca; it has to reprice what is left as a new combination, and the revised odds should show on the settled bet. Some operators split the rule further by sport, by market type or by whether the bet was placed online or in a shop, so a rule you have read for football player markets may not carry over to racing or cricket.

What I look for first is the void clause for the exact sport, before the price.

Promotions sometimes bend the losing-leg rule as well, paying out on the remaining legs if just one selection fails. Where such an offer comes as a token or free bet, read whether returns are paid in cash or as winnings only without the stake, because that changes what the offer is actually worth.

The two get confused constantly, and the names do not help. An accumulator combines selections from different events, such as three Premier League home wins on a Saturday, and its odds are the plain product of the legs. A bet builder keeps every leg inside one fixture, which is why the bookmaker adjusts the price for how the selections relate to each other.

You will also meet the same product under other labels: same-game multi, same-game parlay, or a bookmaker’s own brand name such as Sky Bet’s Request a Bet. The mechanics are the same, though the number of legs allowed and the markets on offer differ from one site to the next.

Some bookmakers now let you place several builders from different matches inside one bet, which is effectively an accumulator of bet builders and carries both sets of rules at once. In that case each match is priced for correlation on its own, the match totals are then multiplied together, and a void leg in any one game is settled under whichever builder rule that operator applies. It is the most complicated bet slip most punters will ever put on, and the hardest one to check by hand.

Acca insurance offers, where they exist, are often written for standard accumulators only, so check whether a builder qualifies before assuming it does.