A driver instrument for engaging and transferring rotational torque to a bone anchor already screwed into a bony structure. The driver instrument may be advanced through an incision while disengaged from the bone anchor and thereafter engaged in a driver socket of the bone anchor. The driver instrument includes an elongate shaft extending distally from a handle, a tapered distal tip, and a driver engagement feature located proximally of the tapered distal tip. The tapered distal tip and the driver engagement feature are configured such that the longitudinal rotational axis of the driver instrument automatically moves into parallel alignment with the longitudinal rotational axis of the bone anchor as the driver engagement feature of the driver instrument is advanced into the driver socket of the bone anchor.