Chiropractic Billing Guide 2026: CMT Codes, AT Modifier, and Medicare Rules

By RCMAXIS Coding Team  ·  June 2026  ·  12 min read

Chiropractic billing operates under a unique set of rules that differ significantly from standard medical billing. The combination of Medicare's strict subluxation documentation requirements, the mandatory AT modifier, and the nuanced CMT code selection criteria makes chiropractic one of the highest-denial specialties in outpatient care. This guide covers every critical billing rule you need to maximize collections and minimize audit risk in 2026.

1. CMT Codes: Selecting the Right Level

Chiropractic Manipulative Treatment (CMT) codes are billed based on the number of spinal regions treated, not the complexity of the visit or the time spent. There are five spinal regions: cervical, thoracic, lumbar, sacral, and pelvic. Selecting the wrong region count is the most common coding error in chiropractic billing.

Critical rule: The number of spinal regions must match exactly what is documented in the SOAP note. Billing 98941 when only the lumbar and sacral regions are documented is upcoding — a common audit trigger. Each region treated must have a corresponding subluxation finding documented.

2. The AT Modifier: Medicare's Gateway to Payment

For Medicare patients, chiropractic CMT codes (98940–98942) must be appended with modifier AT (Acute Treatment) to receive payment. Without AT, Medicare will automatically deny the claim as maintenance care, which is explicitly non-covered.

AT vs. Non-AT Billing: The Distinction

• With AT modifier: Patient must have an acute or subacute condition that is actively improving (or has expectation of improvement). Medicare covers this.
• Without AT modifier: Maintenance care — keeping a stable condition from deteriorating. Medicare does NOT cover this. Bill patient directly (with proper ABN on file).

The key documentation question for every Medicare visit: Is this patient making measurable functional improvement? If yes, use AT. If the patient has plateaued and treatment is maintaining function, that is maintenance care — document accordingly, issue an ABN, and bill the patient directly.

Advanced Beneficiary Notice (ABN) Requirements

When a Medicare patient transitions from active/acute to maintenance care, you must issue a signed ABN (Form CMS-R-131) before the maintenance visit. The ABN informs the patient that Medicare will not cover the service and they will be responsible for payment. Failure to obtain a signed ABN before a non-covered service means you cannot bill the patient — you absorb the cost.

3. Subluxation Documentation: The Foundation of Every Claim

Medicare requires documentation of subluxation as the basis for chiropractic coverage. Subluxation must be documented using one of two methods:

Method 1: X-ray Evidence

A documented X-ray finding showing subluxation. The X-ray must be taken by or for the treating chiropractor and must correlate with the region being treated.

Method 2: Physical Examination Evidence (P-A-R-T)

In the absence of X-ray evidence, subluxation must be demonstrated through physical examination using the P-A-R-T criteria:

• P — Pain/tenderness: Documented at the site of subluxation
• A — Asymmetry/misalignment: Documented on static or motion palpation
• R — Range of motion: Abnormality documented with objective measurements
• T — Tissue/tone changes: Documented muscle spasm, hypertonicity, or atrophy

At least two of the four P-A-R-T components must be documented for each subluxation. Many practices document all four to avoid any vulnerability during audits.

4. Manual Therapy and Other Billable Codes

CMT codes cover spinal manipulation only. Chiropractors often provide additional services that are separately billable — when documented as distinct, medically necessary services that go beyond the manipulation itself.

5. Medicare's 12-Visit Rule and Plan of Care Requirements

While Medicare does not have a hard visit limit for chiropractic, it requires that each visit have documented medical necessity. In practice, Medicare closely scrutinizes claims beyond 12 visits per episode of care. Best practices:

• Establish and document a formal Plan of Care (POC) at the initial visit with specific, measurable treatment goals and expected visit frequency/duration
• Re-evaluate and update the POC every 12 visits or when goals are met
• Document objective functional improvement at re-evaluation (e.g., pain score reduction, increased ROM, improved ADL function)
• When the patient plateaus, transition to maintenance documentation and issue ABN

6. Common Denial Reasons and How to Prevent Them