The term ‘Green Booking’ simply refers to any situation on an exchange where you make a series of bets that end up with every outcome of a game winning you money. It works through a combination of backing and laying, and can enable you to guarantee wins long before a game is over.
Tennis Trading Example:
Say you back Andy Murray to beat Roger Federer in a tennis match. The starting prices look as follows:
Back: 4/Lay: 4.1
Back: 1.25/Lay: 1.26
Say we back Murray for £10, giving us a total profit of £40 if he wins the match (our £10 stake plus our £30 win). Murray then goes on to win the first set. From the way he is moving, we decide that despite winning the first set, he probably will not be able to go the distance and want to secure some profit now. During the interval the prices now look as follows:
As we have already got £40 profit if Murray wins the match, we can use that same money to bet against him and guarantee a profit, and depending on exactly how much we want to green book, we simply reinvest at the now lower odds. In this case we might bet £15 of our £40 win profit on Murry to lose, earning us £20 if he loses (£15 at odds of 2.00 is a total win of £30, minus our initial £10 stake on Murray to win), and £25 if he wins (our initial £40 profit minus the £15 we used to lay against him). Leaving us free to ignore the end result, as we make a nice win regardless of what actually happens.