CAS (X12)
X12 CAS segment, the line that itemizes why an 835 paid less than was charged.
Definition
CAS appears at claim level (loop 2100) and service level (loop 2110). CAS01 is the adjustment group code — CO (Contractual Obligation), PR (Patient Responsibility), OA, PI or CR — followed by up to six CARC/amount/quantity triplets. The sum of all CAS amounts must reconcile billed minus paid.
Origin
Defined in ASC X12N TR3 005010X221 (835) and reused in the 837; group codes are governed by ASC X12. Reason codes referenced come from the external Claim Adjustment Reason Code list maintained by WPC (Washington Publishing Company) for X12.
Example in context
CAS*CO*45*30.00~ — group code CO (contractual), CARC 45 (charge exceeds fee schedule/allowed amount), 30.00 written off.