A medication delivery device comprising a housing, a screw element, a sensing system, and an electronics module, the screw element screwable within and relative to the housing from a dosing position to a zero position during dose delivery, and the sensing system for determining the zero position, the sensing system comprising: at least one actuator member (130, 135) mounted to be movable around the screw element from a first angular position to a second angular position, said at least one actuator member including a push surface; a biasing member arranged to resist motion of said at least one actuator member (130, 135) from said first position to said second position, said biasing member being preloaded when said at least one actuator member is at the first position, said at least one actuator member and the screw element including cooperating stop elements (180, 191) to prevent said at least one actuator member from moving past the first position under the preloaded biasing of said biasing member; a stop surface structured and arranged within the housing for abutment by said push surface as the screw element, with said at least one actuator member (130, 135), screws relative to the housing towards the zero position from the dosing position during dose delivery, the abutment preventing further screwing of said at least one actuator member relative to the housing, and forcing said at least one actuator member to move around the screw element from said first position to said second position against resistance provided by said biasing member, as the screw element continues to be screwed relative to the housing to the zero position; and a sensor within the electronics module adapted to recognize said at least one actuator member (130, 135) moving around the screw element and reaching said second position thereby to sense that the zero position has been reached. at least one actuator member (130, 135) mounted to be movable around the screw element from a first angular position to a second angular position, said at least one actuator member including a push surface; a biasing member arranged to resist motion of said at least one actuator member (130, 135) from said first position to said second position, said biasing member being preloaded when said at least one actuator member is at the first position, said at least one actuator member and the screw element including cooperating stop elements (180, 191) to prevent said at least one actuator member from moving past the first position under the preloaded biasing of said biasing member; a stop surface structured and arranged within the housing for abutment by said push surface as the screw element, with said at least one actuator member (130, 135), screws relative to the housing towards the zero position from the dosing position during dose delivery, the abutment preventing further screwing of said at least one actuator member relative to the housing, and forcing said at least one actuator member to move around the screw element from said first position to said second position against resistance provided by said biasing member, as the screw element continues to be screwed relative to the housing to the zero position; and a sensor within the electronics module adapted to recognize said at least one actuator member (130, 135) moving around the screw element and reaching said second position thereby to sense that the zero position has been reached.