Decode UPS Tracking Number TRACKING #: 1Z XXX XXX YY ZZZZ ZZZC X = Shipper’s Account # (6 Digits) Y = Service Code (2 Digits) (See Partial Key Below) Z = Shipper’s Reference # (Can be set by shipper for convenience, to mirror an invoice#, etc.) C = Check Digit Service Codes 01 UPS United ...