Medicare Chiropractic Billing: CMT Codes and the AT Modifier

Medicare’s chiropractic benefit is the narrowest in outpatient care, and most billing problems chiropractors have with Medicare come from treating it as broader than it is. The statute covers exactly one thing: treatment by means of manual manipulation of the spine to correct a subluxation. Three CPT codes, one modifier that determines whether you get paid, and a documentation standard that is more specific than almost anywhere else in the program.

This guide works from the Medicare Benefit Policy Manual, Chapter 15, §240 (Pub. 100-02), which contains the complete coverage and documentation framework. Current as of August 2026.

What’s covered: three codes

The covered service is chiropractic manipulative treatment of the spine, billed with:

The five spinal regions for counting purposes are cervical (including atlanto-occipital), thoracic (including costovertebral and costotransverse joints), lumbar, sacral, and pelvic (sacroiliac). CMT codes are untimed: one unit per session, regardless of duration, and Medicare limits payment to one treatment per day (§240.1.5, which specifically calls out and rejects the multiple-daily-visit “intensive care” pattern).

98943, the extraspinal CMT code (head, extremities, ribs, abdomen), is not covered by Medicare: the statutory benefit is spinal manipulation only. Hand-held manual devices may be used, but there’s no additional payment for the device (§240.1.1).

What’s excluded: everything else a DC does

This is the part that surprises practices. Under Medicare, when furnished or ordered by a chiropractor (§240.1.1):

• No other service is covered. At all. Not evaluation and management visits, not X-rays, not therapy services (97110, 97140, and the rest), not modalities, not supplies, not orthotics.
• X-rays a chiropractor orders, takes, or interprets are not covered, though they can still be used to document subluxation for claims purposes. The same X-ray is covered when ordered, taken, and interpreted by an MD or DO.
• Chiropractors also cannot certify therapy plans of care (§220.1.3.C), so a DC referral can’t anchor Medicare PT episodes in a multidisciplinary clinic.

Excluded doesn’t mean you can’t furnish these services; it means Medicare won’t pay, and the patient can, with proper notice. For statutorily excluded services (like an exam or 97-series therapy by a DC), the beneficiary is financially responsible; a GY modifier flags the line as statutorily excluded when you bill to generate a denial for secondary insurance. This is different from the AT/maintenance situation below, which uses the ABN and GA/GZ. Getting the two frameworks confused is a common front-desk failure that turns into patient-relations damage later.

The subluxation requirement

Coverage requires a subluxation of the spine, demonstrated one of two ways (§240.1.2):

1. By X-ray, taken within 12 months before or 3 months after starting the course of treatment (older films are acceptable for chronic conditions like scoliosis; CT and MRI evidence also qualifies). An X-ray has not been required since January 1, 2000, but remains an option.
2. By physical examination, using the four criteria the manual enumerates: Pain/tenderness, Asymmetry/misalignment, Range-of-motion abnormality, and Tissue/tone changes (the PART exam). Coverage requires documenting two of the four, and one of the two must be asymmetry/misalignment or range-of-motion abnormality. Pain alone never qualifies; pain plus tissue changes doesn’t either.

Two related coding facts. The primary diagnosis must be subluxation, stated as such or by an acceptable descriptive term (the manual lists examples: misalignment, listhesis, restricted motion). And the precise level must be specified (C5-C6, occipito-atlantal, L5-sacrum); “low back pain” is a symptom, not a level. The symptoms must bear a direct causal relationship to the level cited: the manual explicitly says a claim stating there is “pain” is insufficient without location and a vertebra capable of producing it.

The AT modifier: the coverage switch

Medicare divides chiropractic care into three clinical situations (§240.1.3):

• Acute subluxation: a new injury where manipulation is expected to improve or arrest deterioration. Covered.
• Chronic subluxation: a longstanding condition not expected to resolve, but where continued treatment can still produce some functional improvement. Covered.
• Maintenance therapy: care that prevents disease, promotes health, or maintains a condition after clinical status has stabilized, when “further clinical improvement cannot reasonably be expected.” Not covered, ever, under the chiropractic benefit. (Note this is a harder line than the therapy benefit’s post-Jimmo maintenance coverage; the chiropractic statute has no equivalent.)

The AT modifier is how you tell Medicare which situation applies. The rules are unforgiving in one direction and audited in the other:

• No AT = automatic denial. Claims for 98940–98942 without AT “will be considered as maintenance therapy and denied” (§240.1.3.A). There is no manual review of unmodified claims; the modifier’s absence is the determination.
• AT is an attestation, not a password. The manual warns that the presence of AT “may not in all instances indicate that the service is reasonable and necessary,” and contractors may deny after medical review. Chiropractic has appeared in OIG improper-payment work for years, and blanket-AT billing on long, unchanging treatment histories is exactly what gets sampled.
• When care genuinely is maintenance: no AT, and issue an ABN before treating so the patient understands they’re paying; append GA (ABN on file) so the denial assigns liability correctly, or GZ in the rare case no ABN was obtained (§240.1.3.A).

The clinical trigger for switching off AT is written into the coverage definition: “Once the clinical status has remained stable for a given condition, without expectation of additional objective clinical improvements,” treatment is maintenance. Your documentation of objective change, visit to visit, is what makes the acute/chronic claim defensible.

The documentation requirements, visit by visit

Chiropractic is one of the few benefits where the manual scripts the note contents explicitly (§240.1.2.A–B).

Initial visit must document all six:

1. History: symptoms causing the visit, family history if relevant, past health history, mechanism of trauma, quality/character of symptoms, onset/duration/intensity/frequency/location/radiation, aggravating and relieving factors, prior interventions.
2. Present illness description with symptoms bearing a direct relationship to the subluxation level.
3. Physical exam (the PART evaluation above).
4. Diagnosis: subluxation as primary, with level.
5. Treatment plan: recommended duration and frequency of visits, specific goals, and objective measures to evaluate effectiveness.
6. Date of initial treatment.

Every subsequent visit must document:

1. History: review of chief complaint, changes since last visit, relevant system review.
2. Physical exam of the involved spinal area, assessment of change since last visit, and evaluation of treatment effectiveness.
3. The treatment given that day.

Read requirement 2 again, because it’s the audit divider: every visit needs an assessment of change and treatment effectiveness, which is precisely what identical copy-forward notes cannot show. A record of thirty visits with the same exam findings is, by the manual’s own coverage logic, a record arguing the care is maintenance.

The manual also sets expectations on duration (§240.1.5): acute problems “may require as many as three months of treatment,” front-loaded and decreasing in frequency. Chronic conditions may take longer but not at higher frequency. Episodes that run indefinitely at constant frequency contradict both patterns.

Contraindications worth knowing are documented

The manual lists relative contraindications to dynamic thrust (osteoporosis-level demineralization, anticoagulant therapy, benign spinal bone tumors, progressive radiculopathy, joint hypermobility), and absolute ones near the site of manipulation (spinal malignancy, vertebral infection, acute fracture or unstable dislocation, acute inflammatory arthropathies, myelopathy or cauda equina signs, vertebrobasilar insufficiency for cervical work, nearby aortic aneurysm) (§240.1.3.B). For the relative list, the manual expects the risk discussion with the patient to be recorded in the chart.

Commercial payers: a different world

Everything above is the Medicare frame. Commercial plans and cash practice generally reimburse chiropractors for E/M visits, 98943, and the 97-series therapy codes within state scope of practice, and the timed 97-series codes then follow the unit-counting rules we cover in the 8-minute rule guide (including the Medicare-vs-AMA counting split that varies by payer contract). The operational challenge for a chiropractic practice is running both rule sets side by side without letting commercial habits leak into Medicare claims: the 97110 that’s routine for your BCBS patients is a statutory exclusion on the Medicare patient in the next room.

Denial-prevention summary

• Bill only 98940–98942 to Medicare for covered care; 98943 and everything else is excluded when furnished by a DC.
• AT on every active/corrective treatment claim; no AT plus an ABN and GA when care becomes maintenance.
• Primary diagnosis is subluxation, with the precise level, causally tied to documented symptoms.
• PART exam documented with 2 of 4 criteria, one being asymmetry/misalignment or ROM abnormality (or a qualifying X-ray).
• Every subsequent visit shows change assessment and treatment effectiveness; no copy-forward chains.
• One treatment per day; expect acute episodes to taper.

Running two incompatible rule sets is a systems problem before it’s a compliance problem. PrismEHR lets organizations define their own billing rules, including restrictions by code and payer, enforced at the point of documentation and reinforced at claim creation, which is how a practice keeps its Medicare claims inside the statutory lines while billing commercial plans normally. See how it fits chiropractic practices, or start with the denial-prevention guide for the rest of the rehab billing picture.