The payer looked at a service line and decided the diagnosis attached to it does not support that procedure.
Two chiropractic patterns dominate. Either the diagnosis pointers are misassigned, so a therapy line points at a diagnosis meant for the adjustment, or a spinal CMT code went out without a subluxation level diagnosis the payer requires for that region.
A claim carries three service lines: 98941, 97140, and an exam. The biller pointed all three lines at the same lumbar diagnosis, but the 98941 was billed for three to four regions and the payer expects supporting subluxation diagnoses for each treated region. The CMT line comes back CO-11 while the other lines pay, and the remittance gives no further hint.
For Medicare, the Benefit Policy Manual, Chapter 15, section 240 requires a subluxation demonstrated by X-ray or physical examination, and the treated region must correspond to the documented subluxation.
The denial worklist flags the exact line and pointer at fault, and the scrubber validates CMT region to diagnosis agreement before submission so most CO-11 denials never happen.
General information for billing teams, not legal or payer specific advice. CARC definitions belong to X12; payer policies vary and control. Verify against the payer contract before acting on any individual claim.