Case Study // Chiropractic Billing Services

The AT modifier holds up only when your note proves active, corrective care

Medicare pays chiropractic spinal manipulation (98940, 98941, 98942) only when the AT modifier signals active treatment with a documented plan toward measurable improvement. The turnaround was never about the modifier itself. It was about separating documented corrective care from maintenance, then routing every maintenance visit through a clean ABN workflow so nothing got billed to Medicare that Medicare will not cover.

98940–42The only chiropractic codes Medicare covers, spinal CMT only

Ch. 15Medicare Benefit Policy Manual section that defines active treatment

CMS-R-131The ABN form that makes the patient financially responsible for maintenance

The archetype

A five-provider chiropractic clinic, watching AT claims come back as maintenance

A mid-size chiropractic practice, high Medicare mix, was appending AT to nearly every spinal manipulation and getting a growing share denied as maintenance therapy. The front desk had no way to tell a corrective-care visit from a wellness visit, so the ABN was either missing or handed out blanket-style. Two problems, one root cause: the clinical note did not distinguish active treatment from maintenance, so the payer decided for them.

The core distinction CMS draws: Active/corrective treatment has a reasonable expectation of improvement toward a documented functional goal. Once the patient plateaus and care becomes supportive, it is maintenance, and maintenance is not a covered Medicare benefit no matter how the claim is coded. Appending AT to a maintenance visit is not a billing trick, it is a compliance exposure.

The comparison matrix

Active treatment vs maintenance, line by line

This is the grid the clinical and billing teams now share. If a visit lands in the right column, it does not go to Medicare with an AT modifier. It goes through the ABN workflow.

Dimension

Active / Corrective

Maintenance

Clinical intent

Restore function after an acute or chronic subluxation with a reasonable expectation of improvement.

Preserve or prevent decline once maximum therapeutic benefit is reached.

What the note must show

Precise level of subluxation, mechanism, measurable functional deficit, and a treatment plan with frequency, duration, and goals.

Symptoms stable or plateaued; care is supportive; no expectation of further measurable gain.

Medicare coverage

Covered when medically necessary and documented.

Not a covered benefit. Patient responsibility.

Modifier

AT appended to 98940 / 98941 / 98942.bills to Medicare

No AT. Add GA (ABN on file) so denial routes to patient.ABN required

Financial workflow

Standard claim; expect payment when documentation supports necessity.

Signed ABN (CMS-R-131) before the visit; patient pays; optional claim with GA for a denial on record.

The trap the AT modifier hides: AT tells Medicare "this is not maintenance." It does not prove medical necessity on its own. On audit, the note carries the claim. AT with a thin note is exactly what triggers the maintenance denial and the takeback.

Coverage boundary

What Medicare actually covers for chiropractic

The covered universe is narrow. Everything outside these three codes is either statutorily excluded or a plan-specific question.

98940CMT, spinal, 1–2 regions · AT-eligible

98941CMT, spinal, 3–4 regions · AT-eligible

98942CMT, spinal, 5 regions · AT-eligible

98943CMT, extraspinal · statutorily excluded by Medicare, use GY

Medicare does not cover exams, x-rays, therapies, or extraspinal manipulation ordered by a chiropractor. Those are separate patient-responsibility or referral conversations, not AT-modifier claims. Keep them off the covered claim entirely.

The fix

The ABN workflow that made maintenance visits safe to see

The practice did not stop offering maintenance care. Patients wanted it. The change was giving the front desk a decision path so maintenance never touched a Medicare claim without an ABN behind it.

Classify at check-in

Provider flags each visit active or maintenance against the matrix before the patient leaves.

Active path

Note proves subluxation, deficit, and goal. Claim goes out with AT.

98941-AT

Maintenance path

Patient signs a visit-specific ABN before service. No blanket forms.

CMS-R-131

Bill correctly

Collect from patient. If a denial is needed for a secondary, submit with GA.

98941-GA

Audit the split

Monthly review of AT vs GA ratio catches drift back toward blanket AT.

On the ABN itself: it must be visit-specific, name the maintenance service, give an estimated cost, and be signed before the service. A stack of pre-signed blanket ABNs does not transfer financial liability and will not survive review. That single discipline is what turned maintenance from a write-off into collected revenue.

The guidelines, by name

What this workflow is built on

MBPM

Medicare Benefit Policy Manual, Chapter 15, Section 240 defines covered chiropractic services and the active-treatment standard: a reasonable expectation of improvement distinguishes covered care from non-covered maintenance therapy.

CPM

Medicare Claims Processing Manual, Chapter 12, Section 220 sets the billing mechanics: spinal CMT 98940–98942 with the AT modifier for active/corrective treatment, and the requirement that the record support medical necessity.

ABN

CMS Advance Beneficiary Notice of Noncoverage (Form CMS-R-131) is the instrument that shifts financial liability for maintenance visits to the patient, paired with the GA modifier when a claim is submitted for denial.

MAC

Your MAC's Local Coverage Determination for chiropractic services (for example Novitas or Noridian LCDs) specifies documentation elements and subluxation demonstration your notes must carry to defend the AT modifier on audit.

PFS

CY 2026 Medicare Physician Fee Schedule Final Rule sets the payment amounts for the covered CMT codes; the coverage rules above govern whether those payments hold.

Where it landed

The operational outcome

The wins were structural, not one-time recoveries. The reporting below reflects the shape of the turnaround; exact figures vary by practice and payer mix.

AT → GAEvery visit now routes to one of two clean paths instead of blanket AT

ABN firstMaintenance revenue collected at point of care instead of written off

Audit-readyNotes tie each AT claim to a documented subluxation, deficit, and goal

Fewer takebacksMaintenance denials stopped landing as unexpected Medicare recoupments

Your AT denials are a documentation problem, not a coding problem

ASP-RCM Solutions builds the active-vs-maintenance decision path into your chiropractic billing workflow: note templates that defend the AT modifier, a front-desk ABN process that actually transfers liability, and a monthly audit of your AT-to-GA ratio so drift never rebuilds. Real CMS rules, clean documentation, collected maintenance revenue.

Talk to our chiropractic billing team

Educational content for chiropractic billing operations. Coverage determinations depend on your MAC's current LCD and the CY 2026 Medicare Physician Fee Schedule. Verify code-level requirements against Medicare Benefit Policy Manual Ch. 15 and your local coverage policy before billing.