A monitoring system signals a low bag supply condition in a bag supply of a self-checkout station before the bag supply is depleted and requires immediate attention to enable use of the self-checkout station. The monitoring system includes a low bag supply sensor that detects the removal a bag from the bagwell of the self-checkout station. A counter then records the detection of a bag removal either by incrementing an accumulated count of removed bags or by decreasing a count of the number of bags in a supply. A signal generator generates a low bag supply signal in response to the count exceeding a low bag supply threshold. The threshold corresponds to the number of remaining bags or the number of bags removed depending upon the direction of the counting. The low bag supply signal may be a visual or audible signal sent to an attendant's station so the attendant may schedule the replenishment of the bag supply at a time when the self-checkout station is not being heavily used. The bag removal sensor may be a scale monitor, a movable arm that engages the bags of the bag supply, or a radiation detector that recognizes fluctuations in radiation levels as bag removals. The monitoring system enables an attendant of multiple self-checkout stations to remain available for customer assistance rather than being diverted by station maintenance.