Chiropractic Billing Services · AT Modifier Denials

The AT modifier is not optional. But it is only as strong as your note.

Here is the short answer: Medicare covers chiropractic manual manipulation (98940, 98941, 98942) only for active, corrective treatment of a documented subluxation. The AT modifier is how you tell Medicare the care is active rather than maintenance. Append it and you get paid. Leave it off and the claim is treated as non-covered maintenance. Append it without documentation that proves active treatment, and a post-payment review takes the money back with interest.

Codes: 98940 / 98941 / 98942 Modifier: AT = active/corrective Risk window: post-payment audit

The covered benefit

Three CMT codes, one narrow benefit

Under the Medicare Benefit Policy Manual (Pub. 100-02), Chapter 15, Section 240, Medicare Part B covers only manual manipulation of the spine to correct a subluxation. Nothing else the chiropractor performs is a covered Medicare service. The code you bill has to match the spinal regions you actually treated.

98940

1 to 2 regions

Spinal CMT, one or two of the five spinal regions. Undercoding here is common and leaves revenue on the table when three regions were documented.

98941

3 to 4 regions

Spinal CMT, three or four regions. The most audited of the three. Each region billed must carry a documented subluxation and treatment.

98942

5 regions

Spinal CMT, all five regions. High scrutiny. Reviewers expect every region supported by PART findings, not a template.

The line the AT modifier draws

Active treatment vs maintenance care

The AT modifier certifies active/corrective treatment: care with a reasonable expectation of functional improvement. When the condition has stabilized and further care only maintains that level or prevents decline, it becomes maintenance therapy, which Medicare does not cover. Your note has to make one side of this table obviously true.

BILL WITH AT Active / corrective

Acute or chronic subluxation with a treatment goal of improvement
Documented, measurable functional gains visit to visit
A dated treatment plan with frequency, duration and specific goals
An exacerbation or new injury that restarts an active course

NO AT · NON-COVERED Maintenance

Care to prevent regression or preserve current status
Notes that say "supportive," "maintain," "wellness," or "PRN"
Improvement has plateaued with no new measurable goal
Indefinite frequency and no functional endpoint in the plan

The pre-submission AT checklist

RUN BEFORE EVERY CMT CLAIM

Eight gates that separate documented active treatment from maintenance care. If any gate fails, the AT modifier will not hold up when a MAC pulls the chart on post-payment review. Clear all eight and the note defends itself.

GATE 01

Subluxation is documented, not assumed

PART findings (Pain, Asymmetry, Range of motion, Tissue changes) or an X-ray, with the precise vertebral level named.

GATE 02

Regions treated match the code billed

The number of subluxated regions supports 98940, 98941 or 98942. No billing five regions off a two-region note.

GATE 03

Initial visit captures history and onset

Mechanism, symptom onset and how the subluxation relates to the presenting complaint. This anchors medical necessity.

GATE 04

A dated treatment plan exists

Specific functional goals, recommended frequency and expected duration. An open-ended plan reads as maintenance.

GATE 05

Each visit shows measurable progress

Objective, functional change (ROM degrees, ADLs, pain scale tied to function). "Patient feels better" is not evidence.

GATE 06

Active intent is stated in words

The note reflects an expectation of improvement, not preventing decline or preserving current status.

GATE 07

AT is appended to the CMT line

The AT modifier sits on 98940 / 98941 / 98942 itself, and every diagnosis on the claim supports the manipulation.

GATE 08

The plateau plan is decided in advance

When gains stop, the chart flips to maintenance (no AT) or discharge. AT never rides along on a stabilized patient.

Why AT alone does not save you

The modifier is a claim; the chart is the proof

The AT modifier is not submitted with supporting documentation up front. That is exactly the trap. The claim pays clean, then a MAC selects it for post-payment or TPE review, requests the record, and applies its Local Coverage Determination documentation standards to what the note actually says. If active treatment is not on the page, the payment is recouped even though AT was present.

STEP 1Claim pays

98941-AT clears at adjudication. No documentation was reviewed.

→

STEP 2MAC pulls the chart

Post-payment or Targeted Probe and Educate request against the LCD.

→

STEP 3Recoupment

No documented active treatment means AT was unsupported. The money goes back.

Cite these by name

The guidelines this checklist is built on

Medicare Benefit Policy Manual (CMS Pub. 100-02), Chapter 15, Section 240 the chiropractic services benefit: coverage is limited to manual manipulation of the spine to correct a subluxation.
Medicare Claims Processing Manual (CMS Pub. 100-04), Chapter 12, Section 220 defines CPT 98940, 98941, 98942 and the requirement to report the AT modifier on active/corrective treatment.
National Coverage Determination 150.1, Chiropractic Services maintenance therapy is not a covered Medicare service; active treatment is the coverage line.
MAC Local Coverage Determinations and LCD documentation articles Novitas, NGS, CGS, Palmetto and WPS each publish the PART exam and treatment-plan documentation each visit must contain.
CY 2026 Medicare Physician Fee Schedule Final Rule the current-year rates and payment policy that set what each covered CMT code is worth when the AT support holds.

Stop losing clean claims to a documentation gap

ASP-RCM Solutions builds this AT checklist directly into chiropractic billing workflows, so the note is scrubbed for active-treatment evidence before the claim ever goes out, plateau patients are flagged off AT automatically, and your records are audit-ready before a MAC ever asks. That is how CMT revenue survives post-payment review instead of funding a recoupment.

Get an AT modifier audit of your CMT claims →