Apparatus for singling sheet material, in particular bank notes, which is inputted into an input area of the apparatus as a stack and is transported up to a singler, which transfers individual pieces of sheet material of the stack of sheet material to a sheet transport system, which transports the singled sheet material in a transport direction, a sensor disposed in transport direction upstream of the singler, which substantially extends over the width of the input area, generating signals which specify whether and in which area of the width of the input area the sheet material is present, and a control device evaluating the signals of the sensor during a transport of the stack of sheet material to the singler and comparing occurring fluctuations and changes of the signals of the sensor regarding the presence or absence of sheet material with predetermined threshold values for fluctuations and changes of the signals of the sensor, in order to derive a statement from the occurring fluctuations and changes of the signals of the sensor, whether the pieces of sheet material forming the stack of sheet material are aligned to each other with respect to their edges, and whether the stack of sheet material has an alignment which substantially is in parallel to the transport direction of the transport system.