|Tag||Field Name||Abbr Name||Data Type||Union Datatype||Description||Pedigree|
|66||ListID||ListID / ID in ProgramTrading||String|
Unique identifier for list as assigned by institution, used to associate multiple individual orders. Uniqueness must be guaranteed within a single trading day. Firms which generate multi-day orders should consider embedding a date within the ListID field to assure uniqueness across days.