Customers with a valid Monthly Pass loaded on their Clipper® card can purchase one Monthly Parking Permit per month at Caltrain station ticket machines by entering their unique 10-digit Clipper card number, located on the lower-left back of the card.  (TransLink cardholders also can use this program.)  Parking permits may be purchased between the 21st of the previous month that the permit is valid through the 15th of the month the permit is valid.