Guides Specialty billing

Chiropractic billing: the AT modifier and 98940–98942

By Marlow’s billing manager, 20+ years in medical billing, former billing manager at Mount Sinai South Nassau, Oceanside · Updated November 9, 2026 · 8 min read

The short answer

Medicare pays chiropractors for one thing, manual manipulation of the spine to correct a subluxation, and only while the care is active treatment, which the AT modifier marks. Maintenance care is denied, so it needs a signed ABN and the GA modifier before the patient can be billed.

Medicare covers one chiropractic service: manual manipulation of the spine to correct a subluxation, billed as 98940, 98941 or 98942 by the number of spinal regions treated. It pays only for active or corrective treatment, which the claim marks with the AT modifier. Once the patient’s condition is stable and no further improvement is expected, the care is maintenance, Medicare denies it, and the patient can be billed only if they signed an Advance Beneficiary Notice (ABN) first.

This guide covers what Medicare requires, what the note has to show, how the modifiers fit together, and how New York commercial plans and Medicaid differ. Rules are as of November 2026.

What Medicare covers from a chiropractor

The Medicare Benefit Policy Manual, chapter 15, section 240 limits a chiropractor’s covered services to manual manipulation of the spine to correct a subluxation. Hand-held manual devices are allowed, but Medicare pays nothing extra for them.

Everything else a chiropractor furnishes or orders is not covered when billed by the chiropractor. That includes exams, x-rays, therapy modalities and extraspinal manipulation. An x-ray ordered by a chiropractor can still be covered when an MD or DO takes and interprets it.

Medicare’s manipulation codes, paraphrased (see the CPT book for the official descriptors):

Code	What it covers	Medicare
98940	Spinal manipulation, one or two regions	Covered with AT when active treatment
98941	Spinal manipulation, three or four regions	Covered with AT when active treatment
98942	Spinal manipulation, five regions	Covered with AT when active treatment
98943	Extraspinal manipulation, one or more regions	Not covered for chiropractors

The five spinal regions are cervical, thoracic, lumbar, sacral and pelvic, as listed in the local billing article from Wellpoint Federal (formerly National Government Services), the Medicare contractor for New York. The region count in the note decides the code.

Medicare normally pays one manipulation per patient per day, according to CMS’s documentation checklist for chiropractors. The same checklist notes that chiropractors cannot opt out of Medicare and see Medicare patients under private contracts.

Active treatment and the AT modifier

Section 240.1.3 defines the two kinds of covered problems:

Acute subluxation: a new injury, where treatment is expected to improve the condition or stop it getting worse.
Chronic subluxation: a long-standing condition that won’t resolve, but where continued treatment is expected to bring some functional improvement.

For either one, the chiropractor must put AT on the claim. Two points from the manual decide most disputes:

AT is required, not sufficient. The modifier states that the care is active. The contractor can still review the record and deny if the note doesn’t support it.
No AT means maintenance. A claim for 98940–98942 without AT is treated as maintenance therapy and denied.

Maintenance care

Maintenance therapy is care that keeps a stable condition from getting worse, or promotes general health, once further clinical improvement isn’t expected. The manual says care becomes maintenance when it turns from corrective to supportive. AT must not be used for it.

The ABN and the GA and GZ modifiers

Maintenance care is denied as not reasonable and necessary, so the patient is protected from the bill unless they were warned in writing first. That warning is the ABN.

CMS’s guide to advance written notices defines the modifiers:

Modifier	Meaning	When a chiropractic claim uses it
AT	Active or corrective treatment	Covered manipulation for acute or chronic subluxation
GA	A required ABN was issued and is on file	Maintenance visit, patient signed an ABN
GZ	Expected to be denied as not necessary, no ABN	Maintenance visit without an ABN; the patient can’t be billed
GY	Statutorily excluded service	Services Medicare never covers from a chiropractor, such as exams
GX	Voluntary notice issued for an excluded service	Optional, with GY

So a maintenance visit with a signed ABN is billed with GA and no AT. Medicare denies it, the remittance shows patient responsibility, and the practice collects from the patient. Without the ABN, the visit is a write-off.

What the note has to show

The subluxation

Section 240.1.2 lets the subluxation be shown in one of two ways.

By x-ray, CT or MRI. The image must be reasonably close in time to the start of treatment: taken no more than 12 months before or 3 months after the course of care began. Older imaging can be accepted for some long-term conditions, such as scoliosis. The date of the x-ray goes in item 19 of the CMS-1500 or its electronic equivalent.

By physical exam, using PART. Two of the four findings below are required, and one of the two must be asymmetry or range of motion.

Letter	Finding	What the note records
P	Pain or tenderness	Location, quality and intensity
A	Asymmetry or misalignment	At a sectional or segmental level
R	Range of motion abnormality	Increased or decreased mobility
T	Tissue or tone changes	Changes in skin, fascia, muscle or ligament

Pain plus tissue changes alone does not meet the rule, because neither is asymmetry nor range of motion.

The first visit

The manual lists what the initial record contains: history, a description of the present illness (with symptoms tied to the level of the subluxation), the exam, a primary diagnosis of subluxation with its level, and a treatment plan. The plan should state the recommended frequency and duration of visits, specific goals and the objective measures that will show progress. The date of initial treatment, or the date of an exacerbation, goes in item 14 of the claim.

The precise level must be named, either by the bones (for example C5, C6) or by an area that implies them (for example lumbosacral). A statement that the patient has “pain” is not enough. The note has to say where, and why that vertebra could cause it.

Every later visit

Each subsequent note needs the review of the chief complaint and changes since the last visit, an exam of the spinal area involved, an assessment of change, an evaluation of how the treatment is working against the plan’s measures, and the treatment given that day with the regions and levels manipulated.

Why this matters

CMS calls insufficient documentation a common issue and reports that a 2024 Comprehensive Error Rate Testing (CERT) review found errors in 33.6% of chiropractic claims, in the same checklist. It names the common denial reasons: no response to a records request, missing or thin treatment plans, an unclear chief complaint, and treated regions that aren’t all documented.

How long active care can run

The manual gives no visit cap. It says acute problems such as strains may need up to about three months of treatment, with visits getting less frequent as the patient improves, and chronic problems may need longer, but not more frequent, care. Long or repeated courses are more likely to be reviewed. The treatment plan’s goals and measures are what show the care is still active.

New York commercial plans

New York insurance law requires fully insured policies that cover physician office visits to also cover chiropractic care, under Insurance Law §4303 for nonprofit plans such as the Blues, and matching sections for individual and group policies from commercial insurers (§3216 and §3221). Plans may apply reasonable copays, fee limits and utilization review, but those can be no more restrictive than what the plan applies to other professionals treating the same condition.

What this means for billing:

Visit limits, prior authorization and review vendors vary by plan. Read each plan’s chiropractic policy and note the date of the version you read.
Commercial plans may pay services Medicare doesn’t, such as an exam on the same day as a manipulation with modifier 25, when the note shows a separate evaluation.
The mandate covers policies issued under New York insurance law. An employer plan that pays claims from its own funds may not be one of them, so check chiropractic benefits for each patient rather than assuming the mandate applies.

New York Medicaid

The eMedNY Chiropractor manual (the 2007 policy version eMedNY still posts) limits NY Medicaid fee-for-service payment to chiropractors to Medicare deductibles and coinsurance for Qualified Medicare Beneficiaries (QMBs), on services Medicare approved. Medicaid pays nothing when Medicare denies, and the chiropractor can’t bill the QMB patient for those amounts. Medicaid managed care plans publish their own benefit rules, so check the plan’s provider manual before assuming coverage.

No-fault and workers’ compensation

These are separate systems with their own rules and forms. Workers’ compensation chiropractic care is paid under the NY Workers’ Compensation Board chiropractic fee schedule, and no-fault claims use the WCB fee schedules under DFS Regulation 83. They are outside the scope of this guide.

A short checklist before a Medicare claim goes out

The subluxation is shown by dated imaging or by two PART findings, one of them A or R.
The diagnosis names the subluxation and its level.
The treatment plan has frequency, duration, goals and measures.
The region count in the note matches 98940, 98941 or 98942.
AT is on the line if the care is active; GA (with an ABN on file) or GZ if it is maintenance.
Item 14 has the initial treatment or exacerbation date; item 19 has the x-ray date if imaging is used.
Exams and other non-covered services are not billed to Medicare as covered.

Sources

General information, not advice on a specific claim, contract or legal question. Rules and rates change; check the linked sources for the current version. CPT® is a registered trademark of the American Medical Association. Code descriptions here are paraphrased.