The payer covered the service type but decided this occurrence was not medically necessary.
On Medicare this usually means the patient had drifted into maintenance care while claims still went out with the AT modifier. On commercial plans it is often a utilization review deciding the adjustment schedule outran the documentation.
A personal injury patient reaches maximum improvement in March but keeps coming weekly through June, and the claims keep going out with the AT modifier because nobody changed anything. The payer runs a utilization review and denies the last twelve visits as not medically necessary. On the Medicare version of this story, the right answer was an ABN and the cash rate starting in March.
This denial is the center of chiropractic compliance risk. The HHS Office of Inspector General reported that chiropractic services have the highest rate of improper payments among Medicare Part B services, that past OIG work found 40 to 47 percent of paid chiropractic claims were for maintenance therapy, and that $76 million in 2013 chiropractic payments were questionable. Medicare covers active treatment only; the maintenance boundary is defined in the Benefit Policy Manual, Chapter 15, section 240.
Cervica routes Medicare CO-50s toward the ABN and cash conversion workflow and commercial ones toward an appeal, with AI drafting the appeal letter from the chart on plans that include it.
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.