The federal audits keep finding the same thing: a large majority of chiropractic Medicare payments do not meet the documentation rules. That is not because chiropractors bill dishonestly. It is because the coverage rules are narrow, specific, and unforgiving, and a generic billing system does nothing to enforce them. Here is the whole map.
What Medicare actually covers
This is the part that surprises people. For a chiropractor, Medicare covers exactly three codes, and only under conditions:
| Code | What it is | Covered? |
|---|---|---|
| 98940 | Spinal CMT, 1 to 2 regions | Yes, with AT modifier and subluxation dx |
| 98941 | Spinal CMT, 3 to 4 regions | Yes, with AT modifier and subluxation dx (most common) |
| 98942 | Spinal CMT, 5 regions | Yes, with AT modifier and subluxation dx |
| 98943 | Extraspinal CMT | No, never covered by Medicare |
| Exams / E/M | Office visits, evaluations | No, statutorily excluded |
| 97xxx therapies | Manual therapy, e-stim, traction | No, statutorily excluded for a DC |
| X-rays | Spinal imaging | No, not covered for a DC |
Everything in the "No" rows is not a denial to appeal; it is a service the patient is responsible for. That distinction drives the modifier choices below.
The AT modifier and the subluxation diagnosis
The AT (Acute Treatment) modifier tells Medicare the care is active or corrective, with a reasonable expectation of improvement. It goes on 98940, 98941, or 98942 for every covered visit. Drop it and the claim is denied as maintenance care, which Medicare does not pay, and there is nothing to adjudicate on the merits. Alongside AT, the claim needs a primary subluxation diagnosis, an M99.00 through M99.05 code chosen by spinal region, plus a secondary neuromusculoskeletal diagnosis that explains the symptoms. The visit-by-visit judgment of active versus maintenance care is the line the auditors walk, so the documentation has to support improvement, not just continued treatment.
The non-covered services and the ABN
Because exams, therapies, and x-rays are not covered for a chiropractor, you collect an Advance Beneficiary Notice and use the right modifier so you can bill the patient:
- GA: ABN on file, expected denial, patient can be billed. This is what you want on non-covered services the patient agreed to pay for.
- GZ: no ABN, expected denial. This auto-denies and you cannot bill the patient. It exists to keep you honest, not to get you paid.
- GY: statutorily excluded item. It will deny and the patient is responsible; use it to generate the denial for a secondary payer or the patient.
The pattern that keeps a chiropractic practice solvent: AT on the covered adjustment, and an ABN with GA on the non-covered services performed the same day.
The 97140 edit
Manual therapy (97140) on the same region as the manipulation is bundled into the CMT under NCCI and is not separately payable. If you perform manual therapy on a genuinely different region, it can be billed with modifier 59 or XS, documented as a distinct service. Same region, no modifier can rescue it, and it denies with CO-97. For Medicare, remember that 97140 is non-covered for a DC in the first place, so this mostly matters for commercial payers.
The denials that hit chiropractic hardest
| Code | What it means here | The fix |
|---|---|---|
| CO-50 / CO-96 | Non-covered, usually AT missing or a non-covered service | Add AT for active care; use ABN and GA for non-covered |
| PR-204 (N130) | Service not covered under the plan | Bill the patient with the ABN in hand |
| CO-97 | 97140 bundled into the CMT | Different region plus modifier 59, or do not bill it |
| Maintenance denial | Documentation reads as supportive, not corrective | Document expected improvement, or move the patient to cash |
| Missing M99 dx | No primary subluxation diagnosis | Add the region-specific M99.0x as the primary |
Run any reason code through the denial code decoder to see who owes the balance, and keep the filing deadlines handy so a fixable denial does not expire.
Why generic billing software cannot save you here
A general system does not know that a CMT code needs AT, that the primary diagnosis has to be a subluxation code, or that the exam you just added is non-covered and needs an ABN. ChiroTouch and ChiroFusion exist because that logic has to be enforced, not remembered. A solo or cash-plus-insurance practice that does not want a full chiropractic EHR still needs a scrubber that flags a missing AT before the claim goes out, which is the gap this fills.
Common questions, answered
Does Medicare cover 98941?
Yes, with the AT modifier and a primary subluxation diagnosis. Medicare covers 98940, 98941, and 98942 as active or corrective care. Without AT it denies as maintenance. 98943 extraspinal is never covered.
When do I use the AT modifier?
On every covered CMT code when the care is active or corrective with expected improvement. Not for maintenance. Pair it with an M99.0x primary subluxation diagnosis and a secondary neuromusculoskeletal code.
Do I need modifier 59 for 98940 and 97140 the same day?
Only if the manual therapy was on a different region and documented as distinct, with modifier 59 or XS. Same region bundles into the CMT and denies with CO-97. For Medicare, 97140 is non-covered for a DC regardless.
What is the difference between GA, GY, and GZ?
GA: ABN on file, patient billable. GZ: no ABN, auto-denies, patient not billable. GY: statutorily excluded, patient responsible. Use ABN plus GA on non-covered chiropractic services you intend to bill the patient for.
Why was my 99213 with modifier 25 denied?
If the note reads like the routine pre-adjustment check, the payer bundles the E/M into the CMT (CO-97). Modifier 25 needs a separately identifiable, documented reason. For Medicare, the E/M is non-covered anyway, so it needs an ABN with GA or GY.