A banknote acceptor for authenticating a banknote under test presented thereto by a user, comprising: a sensing station to receive the banknote under test, including a detector configured to provide image signals corresponding to the banknote, a memory to store reference data corresponding to an acceptable banknote, a display device (30,32), characterized by: a processor (23,24) configured to make a comparison of image data corresponding to at least some of the image signals from the detector with the stored reference data corresponding to an acceptable banknote, to determine the authenticity of the banknote under test, and to provide an acceptance signal for the banknote under test in dependence on the outcome of the comparison, the display device configured to display the image signals from the detector for the banknote under test to allow the user to perform a visual check that the banknote detected at the sensing station corresponds to the banknote under test presented thereto by the user, a user operable device (33,34) configured to signal acceptability of the image of the banknote under test provided by the display device for the visual check, and control means configured to accept the banknote under test in dependence on said acceptance signal and the acceptability signalled by said user operable device. a sensing station to receive the banknote under test, including a detector configured to provide image signals corresponding to the banknote, a memory to store reference data corresponding to an acceptable banknote, a display device (30,32), characterized by: a processor (23,24) configured to make a comparison of image data corresponding to at least some of the image signals from the detector with the stored reference data corresponding to an acceptable banknote, to determine the authenticity of the banknote under test, and to provide an acceptance signal for the banknote under test in dependence on the outcome of the comparison, the display device configured to display the image signals from the detector for the banknote under test to allow the user to perform a visual check that the banknote detected at the sensing station corresponds to the banknote under test presented thereto by the user, a user operable device (33,34) configured to signal acceptability of the image of the banknote under test provided by the display device for the visual check, and control means configured to accept the banknote under test in dependence on said acceptance signal and the acceptability signalled by said user operable device. a processor (23,24) configured to make a comparison of image data corresponding to at least some of the image signals from the detector with the stored reference data corresponding to an acceptable banknote, to determine the authenticity of the banknote under test, and to provide an acceptance signal for the banknote under test in dependence on the outcome of the comparison, the display device configured to display the image signals from the detector for the banknote under test to allow the user to perform a visual check that the banknote detected at the sensing station corresponds to the banknote under test presented thereto by the user, a user operable device (33,34) configured to signal acceptability of the image of the banknote under test provided by the display device for the visual check, and control means configured to accept the banknote under test in dependence on said acceptance signal and the acceptability signalled by said user operable device.