Passengers who use the electronic Clipper card to ride must remember to "tag on" with their card prior to boarding and "tag off" with their card after exiting the train. If they board the train without tagging on, they will be subject to the same fines. In addition, Caltrain passengers are charged the maximum one way fare from their originating zone when they tag on prior to boarding the train and the difference is reimbursed when they tag off after leaving the train at their destination zone. If passengers who use the Clipper card fail to tag off when they exit the train, they will be charged "the highest cash fare from point of origin."