The modifier Medicare requires on spinal CMT lines to attest the visit was active corrective treatment rather than maintenance care.
The single highest stakes modifier in chiropractic. With AT, Medicare treats the adjustment as active care and adjudicates it. Without it, the claim is maintenance by definition and denies. And appending AT to visits that are actually maintenance is the precise behavior the OIG has spent years measuring, so the modifier is an attestation, not a keystroke.
A Medicare patient improves through eight weeks of documented active care, all correctly billed with AT. Improvement plateaus and visits become supportive. The correct sequence is the maintenance conversation, an ABN signed before the next visit, the GA modifier replacing AT, and the patient paying the cash rate. Practices that never make that switch are the 40 to 47 percent statistic.
The OIG found 40 to 47 percent of paid chiropractic claims were for maintenance therapy in past reviews, and chiropractic carries the highest improper payment rate among Medicare Part B services. The AT modifier sits exactly on that fault line, which is why auditors read it as a signed statement.
Required on 98940, 98941, and 98942 for active treatment claims, per the Claims Processing Manual, Chapter 12. The maintenance boundary itself is defined in the Benefit Policy Manual, Chapter 15, section 240.
AT on maintenance visits, the core chiropractic compliance failure; missing AT on genuinely active care, which denies clean claims; no ABN process, leaving maintenance visits uncollectable from anyone.
Cervica's claim scrubber validates modifiers, units, and diagnosis pointers for AT modifier before submission, per payer rules handle code substitutions and modifier requirements automatically, and when a payer pushes back anyway the denial worklist reads the adjustment codes and routes the claim to the exact fix.
General information for billing teams, not legal, coding, or payer specific advice. CPT is a registered trademark of the American Medical Association; code descriptions here are paraphrased in our own words and the AMA's CPT publications control. Payer policies vary and control for any individual claim.