A torque sensor system having an index function and ascertaining a torque between an input shaft and an output shaft connected to each other via a torsion bar, includes: a magnetic unit having a magnetic pole wheel for generating a magnetic field, the magnetic unit being rigidly connected to one of the two shafts; a flux ring unit having a flux ring system for converting and conducting the magnetic flux generated by the magnetic unit, the flux ring unit being rigidly connected to the other shaft; and a sensor unit having at least one first magnetic field-sensitive sensor element for sensing changes in the magnetic flux through the flux ring system, the sensor unit being mounted in a stationary manner relative to the flux ring unit. The index function is implemented with the aid of an index magnet and a further magnetic field-sensitive sensor element.