The claim control number is an identifier assigned by the processing system (i.e., the Encounter Data System Contractor) to a claim.
This is the field that, in combination with the original claim control number, identifies a unique version of a service record.
Multiple iterations of a single service (i.e., a particular type of claim for a specific service date for the person) are present in the Encounter RIFs; records are not limited to the final version of the encounter record. When multiple records for a service exist, the higher the claim control number, the later it was adjusted (i.e., the highest CLM_CNTL_NUM is the latest version of the encounter).
Source: CMS Encounter Data System (EDS)