Chiropractic Billing Guide: AT Modifier, CMT Codes, and PIP Claims

Chiropractic billing has unusual rules. Medicare covers exactly one chiropractic service, manual manipulation of the spine, and excludes everything else a chiropractor commonly performs. Commercial payers pay more broadly but apply session caps, prior authorization, and active versus maintenance care distinctions. PIP and workers compensation claims operate under their own rules in each state. Mastering these regimes is what separates chiropractic offices that collect 96% of expected revenue from those stuck under 80%. This guide walks through the high-frequency codes, the modifier framework, and the operational habits that make chiropractic billing reliable.

The CMT code family: 98940-98943

Chiropractic Manipulative Treatment (CMT) is billed using four primary CPT codes. Code selection depends on the number of spinal and extraspinal regions adjusted during the encounter.

The five spinal regions are cervical, thoracic, lumbar, sacral, and pelvic. The extraspinal regions are head, lower extremities, upper extremities, rib cage (excluding costovertebral and costotransverse joints), and abdomen.

• 98940: CMT, 1-2 spinal regions.
• 98941: CMT, 3-4 spinal regions.
• 98942: CMT, 5 spinal regions.
• 98943: CMT, extraspinal, 1 or more regions.

98943 is bundled or non-covered by Medicare and many commercial payers. Practices billing 98943 should know each payer's policy before submitting. Documentation must specify the regions adjusted; vague phrasing like "full spine adjustment" is not sufficient and will fail an audit.

The AT modifier and the active treatment requirement

For Medicare, every covered chiropractic claim must include the AT (active treatment) modifier. AT signals that the service is for the acute or chronic active treatment of subluxation rather than maintenance. Without AT, the claim is denied as non-covered maintenance care.

To support AT, the provider must document:

• A specific subluxation diagnosis (M99.01-M99.05 series) supported by the PART examination findings (Pain/Tenderness, Asymmetry, Range of Motion abnormality, Tissue tone changes).
• A treatment plan with measurable goals.
• Functional outcome measurements at appropriate intervals (Oswestry, Neck Disability Index, etc.).
• Documented progress, plateau, or change in plan over time.

Medicare reviewers focus on whether the documentation supports continued active treatment. Once the patient reaches a clinical plateau or maximum medical improvement, AT is no longer appropriate, and continued care becomes maintenance. CMS chiropractic guidance reinforces this distinction at length.

Maintenance care: the line and how to manage it

Maintenance care is wellness or preventive chiropractic care that aims to keep a patient stable rather than correct an active condition. Medicare excludes maintenance care entirely. Most commercial payers also exclude or sharply limit it. The chiropractic billing challenge is recognizing the transition point and changing the billing accordingly.

Operationally:

1. Establish a treatment plan with defined goals at the start of care.
2. Re-examine at predefined intervals (commonly every 12 visits or 30 days).
3. When the patient reaches maximum benefit, communicate the maintenance transition.
4. Drop the AT modifier. Issue an Advance Beneficiary Notice (ABN) for Medicare patients before continuing service.
5. Bill the patient as self-pay for ongoing maintenance visits.

Practices that bill AT for years on end without documented re-examinations attract audit attention and recoupment.

Medicare's narrow coverage: what is excluded

Medicare statute covers only manual manipulation of the spine performed by a chiropractor. Excluded from Medicare coverage when performed by a chiropractor are:

• X-rays.
• Office visits and evaluation and management codes.
• Therapy modalities (97014, 97035, 97140, etc.).
• Therapeutic exercises (97110).
• Massage therapy (97124).
• Acupuncture (when performed by a chiropractor for non-covered indications).

For Medicare patients receiving these non-covered services, an ABN must be obtained and the service billed with modifier GA or GY depending on the situation. Failure to issue an ABN before non-covered services means the provider cannot bill the patient.

Commercial chiropractic billing: session caps and active care

Commercial plans typically cover a broader scope than Medicare but apply visit caps (e.g., 20 visits per calendar year), prior authorization after a threshold, and medical necessity reviews. Most commercial plans use the AT modifier in the same way as Medicare to delineate active versus maintenance care.

Common commercial denial patterns:

• Visit cap exceeded; further care requires PA or transitions to self-pay.
• Medical necessity denial when functional outcome measures show plateau.
• Therapy modality bundling under PT-style multiple procedure rules.
• Documentation insufficient to support level of CMT (e.g., billed 98942 but only 3 regions documented).

Personal Injury Protection (PIP) claims

PIP claims arise from auto accidents and pay through the patient's auto insurance regardless of fault, in 12 no-fault states and several add-on states. PIP coverage limits, fee schedules, and documentation requirements vary by state. Florida, New York, Michigan, and New Jersey each have distinct PIP regimes.

PIP billing workflow

1. Verify coverage. Confirm PIP carrier, policy limits, deductible, and exhaustion status before treating.
2. Obtain assignment of benefits. Without AOB, the carrier may pay the patient directly.
3. Document mechanism of injury. Date of accident, body parts injured, force vector. State PIP statutes require this in many jurisdictions.
4. Bill the auto carrier as primary. Use the same CPT codes as commercial claims; some states cap fees at the workers comp or Medicare schedule.
5. Track exhaustion. Once PIP limits exhaust, billing switches to health insurance, MedPay, or third-party liability.
6. Manage liens. In third-party liability cases, the chiropractor may bill against a settlement under a treatment-on-lien arrangement.

State-specific PIP rules change often. Practices in PIP-heavy markets should subscribe to the state insurance department alerts and attend annual chiropractic association updates.

X-rays and diagnostic services

Medicare does not pay chiropractors for X-rays. Period. Commercial plans often do, particularly when a separate diagnostic radiology code (e.g., 72020, 72040) is billed with the appropriate ordering and supervisory documentation. Many practices outsource X-rays to a radiology partner or refer the patient for imaging at a hospital or imaging center, billing only the technical or professional component as appropriate.

Chiropractic offices that own X-ray equipment and serve commercial patients should ensure: appropriate state radiology supervision rules are met, the technical component is billed by the entity owning the equipment, and the professional interpretation is documented by a qualified provider.

The Bottom Line

Chiropractic billing rewards a disciplined process: accurate region documentation, conservative AT modifier usage, clear maintenance care transitions, and payer-specific PIP and commercial workflows. Practices that build this discipline collect more, audit cleanly, and avoid the recoupments that periodically devastate cash flow in chiropractic offices that get sloppy.

Related: Chiropractic Billing Services · Medical Coding · Medicare Advantage Guide