This variable is the unique identification number assigned to each formulary. Part D plans submit their formularies to CMS and identify the drug products that are covered using the National Library of Medicine’s RxNorm Concept Unique Identifiers (RXCUIs).
This field is a key that links of Part D sponsor's formulary file to their contract and plan identifiers.
The same formulary may be used by more than one plan benefit package (PBP; variable
called PLAN_ID) within a contract.
The CCW constructs a Formulary Characteristics File from the CMS Approved Formulary
Data found in the CMS’s Health Plan Management System (HPMS).
Source: CMS (HPMS Files)