The invention relates to a method for calibrating a sensor which is configured for checking value documents. The sensor senses measurement signals of a calibration medium which is transported past the sensor. From the sensed measurement signals there are determined reference data of the calibration medium and there is moreover determined a transport property of the calibration medium, e.g. the transport speed or the transport position of the calibration medium. From the transport property there is ascertained at least one correction value which is employed for correcting the sensed reference data of the calibration medium. After the calibration, the corrected reference data are compared with target data of the calibration medium. Optionally there is then effected an adjustment of the sensor using the corrected reference data.