A modular off-platter detection assembly for use with a barcode reader includes a housing, a first light source, a first light sensor, and a controller operatively coupled to the first light source and the first light sensor. The housing is configured to be removably mounted to the barcode reader, a frame supporting the barcode reader, or the workstation. The first light source is positioned within the housing and emits a first light along a first lateral edge of a weigh platter. The first light sensor is positioned within the housing, has a first field-of-view along the first lateral edge, and is configured to detect at least a portion of the first light reflected towards the housing. The controller is configured to provide a first alert in response to receipt of a first value from the first light sensor indicating there is an object extending across the first lateral edge.