Historical version 5 of Carnet (view current version)
A "book" of 10 tube tickets bought in advance for single journeys within zone 1. You can buy them at any touch-screen ticket machine or at the ticket office. Each book costs �15.00, making an individual journey �1.50 - a saving of 50p per journey (normal Z1 single fare �2).
If you make infrequent journeys both within *and* outside Zone 1, you will be better suited with a prepay [Oystercard]? which charges last year's fares everywhere, and a maximum single fare of �1.80 anywhere at weekends. However it does charge �1.60 per journey within Zone 1, 10p more than a Carnet.
See also: Bus Saver Tickets.