Flavour tagging in LHCb, including calibration and control

Many of the precise measurements expected from LHCb will be based on the observation of time-dependent CP asymmetries, which rely on flavour tagging. This article shows that the high precisions aimed for at LHCb impose stringent conditions on both flavour tagging performance and its calibration. The algorithms that have been developed for flavour tagging at LHCb are described, as well as the procedure for obtaining the required level of calibration by using control channels.