Dutch book is a term used in online or other forms of gambling to describe a set of odds and bets that guarantee a profit for the individual, regardless of the outcome of the actual wager. It is based on implied probabilities, given the fact that the odds are never set in stone. It is a fairly common term in financial spread betting, because it refers to a series of trades where one person is left extremely well off while the other is left destitute, although the mathematical principles of consumer choice theory have suggested that there is never a chance of anyone being able to be Dutch-booked and that only the statistically-weaker participants will end up on the losing end.

One of the easiest examples of a Dutch book, in play, is when a bookmaker has offered odds and is taking bets that balance each other out; thus making the result of the actual event completely irrelevant, as the implied probabilities add up to a number greater than one. A very common scenario is where sports betting takes place on a horserace and some form of exotic bet is placed, such as predicting the order in which the horses will actually finish. Punters can sometimes create a Dutch book scenario by using arbitrage betting to select the best odds from several different bookmakers at the same time, while on the flip side the bookmaker can adjust the offered odds based on the demand, thus removing the potential profit. The more bets placed by a punter, the more chances of winning through Dutch booking.