Denials for chiropractic claims happen much more often than expected, and not because the services were never rendered. Chiropractic coverage under Medicare is limited and highly specific, so it only takes one modifier or code that does not line up with the rest of the claim to get the whole thing denied.
This chiropractic billing guide reviews the CPT codes chiropractors use, the ICD-10 codes required to accompany them, the modifiers that determine whether a claim gets paid, and the errors that show up most often in denied claims.
The Core CPT Codes: 98940 to 98943
Chiropractic manipulative treatment, usually called CMT, is billed based on how many spinal regions were treated in a single visit, not how many individual adjustments were made. There are five recognized spinal regions in chiropractic billing: cervical, thoracic, lumbar, sacral, and pelvic.
98940: Covers manipulation of 1 to 2 spinal regions
9894: Covers manipulation of 3 to 4 spinal regions, and it’s the most commonly billed of the three
98942: Covers manipulation of all 5 spinal regions
98943: Covers manipulation of an extra-spinal region, such as the shoulders, knees, wrists, ribs, or TMJ
You can’t bill two of these codes for the same date of service on the same patient. A solid chiropractic billing guide will tell you to pick the one code that reflects the total number of regions actually treated and documented that visit, not the number you usually bill and not a rounded-up estimate.
98943 sits in its own category. Medicare doesn’t cover it under any circumstance, whether the care is active or maintenance. If you’re billing it to Medicare, it needs a GY modifier to flag it as a statutorily excluded service. If it’s billed on the same day as a spinal CMT code, it also needs modifier 59 to show it’s a distinct service at a different site.
Why the AT Modifier Decides Everything
If there’s one thing to get right in any chiropractic billing guide, it’s this. Every Medicare claim for 98940, 98941, or 98942 needs the AT modifier when the treatment is active and corrective.
Medicare’s chiropractic benefit covers exactly one thing: manual manipulation of the spine to correct a subluxation, and only when that manipulation is actively working toward a measurable outcome. Maintenance care, where the goal is simply keeping the patient comfortable rather than correcting a documented condition, isn’t covered at all.
Leave the AT modifier off an active treatment claim, and Medicare reads it as maintenance by default and denies it automatically, often with no chart review and no appeal path. Attach AT to a claim that your own notes describe as maintenance, and you’ve created the opposite problem: a mismatch between the modifier and the documentation, which is one of the most common findings in chiropractic Medicare audits.
The rule of thumb is simple. AT isn’t a default you apply to every claim. It’s a claim you make about the clinical picture, and the chart has to back it up.
When Maintenance Care Starts: GA and GZ
Once a patient plateaus and stops showing measurable improvement, Medicare no longer considers the care active, even if the chiropractor believes ongoing adjustments still have value. At that point, two modifiers come into play.
GA signals that a waiver of liability is on file, meaning the patient signed an Advance Beneficiary Notice of Noncoverage (ABN) acknowledging that Medicare likely won’t pay and they’ll be responsible for the cost.
GZ signals that the service is expected to be denied as not reasonable or necessary, and no ABN is on file.
In practice, this part of a chiropractic billing guide comes down to timing. The moment a patient’s progress plateaus, issue an ABN before continuing treatment, stop appending AT, and bill ongoing visits with GA instead. Continuing to bill AT past the point of documented improvement is one of the patterns that shows up most often in OIG recoupment findings.
ICD-10 Diagnosis Pairing: Getting the M99.0x Codes Right
The primary diagnosis on a Medicare chiropractic claim has to be a subluxation code from the M99.0x family, matched to the specific region treated.
M99.01: for the cervical region
M99.02: for the thoracic region
M99.03: for the lumbar region
M99.04: for the sacral region
M99.05: for the pelvic region
A secondary diagnosis describing the clinical condition, such as low back pain, radiculopathy, or cervicalgia, supports medical necessity alongside the subluxation code. One detail worth flagging for anyone still working from an older code list: as of October 2025, ICD-10 code M54.5 (low back pain, unspecified) was retired and split into three more specific codes, M54.50, M54.51, and M54.59. Any claim still carrying the old M54.5 code will be denied outright, so it’s worth checking that superbills and EHR pick lists have been updated.
Documentation should also reflect PART criteria: Pain/tenderness, Asymmetry, Range of motion abnormality, and Tissue tone changes. At least two of the four need to be present, and one of those two has to be range of motion or tissue tone, to support the subluxation diagnosis at each visit.
Other Modifiers Worth Knowing
Beyond AT, GA, and GZ, a few other modifiers come up regularly in chiropractic billing.
Modifier 25: Gets appended to an E/M code when a significant, separately identifiable evaluation is performed on the same day as a manipulation. Without it, the E/M service tends to get bundled into the CMT code and denied on its own.
Modifier 59: More specific X{EPSU} modifiers unbundle services that would otherwise be considered part of another procedure on the same date, such as billing 98943 alongside a spinal CMT code.
Misapplied modifiers are one of the leading causes of denials industry-wide, not because the underlying code was wrong, but because the modifier told the payer something the documentation didn’t support.
Common Reasons Chiropractic Claims Get Denied
A few patterns account for most of the denials chiropractic practices see, and any practical chiropractic billing guide should walk through them directly.
Missing or Mismatched AT Modifier. Covered above, and still the single biggest driver of automatic denials.
Region Count Mismatch. Billing 98942 when the notes only support manipulation of three regions, or billing 98941 with documentation that only describes two. Payers increasingly run automated checks specifically looking for this pattern.
Generic or Missing Subluxation Coding. Billing a pain code alone, without the corresponding M99.0x subluxation code tied to the region treated, is one of the most common reasons a claim gets flagged for lack of medical necessity.
Maintenance Care Billed as Active Treatment. Once a patient plateaus, continuing to bill AT instead of switching to an ABN and GA isn’t just a denial risk. It’s a compliance issue, and the pattern most likely to trigger a broader audit.
Missing ABN when one was needed. If a service is expected to be denied and no ABN is on file, the practice, not the patient, usually absorbs the cost.
Best Practices for Cleaner Chiropractic Claims
A few habits consistently show up in practices with lower denial rates. Document the exact regions treated at every visit rather than writing a general note. Confirm PART criteria are met and recorded before applying a subluxation code. Review patient progress often enough to catch the plateau point before it turns into a compliance issue. Keep ABN forms current and signed before, not after, a service that’s likely to be denied.
Following these habits consistently is really what separates a chiropractic billing guide from an actual working billing process.
Frequently Asked Questions
Can 98940 and 98941 be billed on the same date of service?
No. Only one CMT code can be billed per patient per date of service, based on the total number of spinal regions actually treated that visit.
Does Medicare cover extraspinal manipulation billed under 98943?
No. Medicare excludes 98943 entirely, regardless of medical necessity. It should be billed with a GY modifier when submitted to Medicare, and coverage under commercial payers varies and should be verified in advance.
What happens if AT is left off an active treatment claim?
The Medicare Administrative Contractor treats the claim as maintenance care by default and denies it automatically, typically without a chart review or an appeal path.
How many PART criteria are required to support a subluxation diagnosis?
At least two of the four: pain/tenderness, asymmetry, range of motion abnormality, and tissue tone changes, with one of the two required findings being range of motion or tissue tone.
Conclusion
Chiropractic billing rewards precision more than most specialties. The right CPT code, the right region count, a subluxation diagnosis that matches the region treated, and a modifier that accurately reflects whether care is active or maintenance all have to line up, or the claim comes back. None of it is complicated once the workflow is built around it. It just has to be built correctly the first time, which is the whole point of putting together a chiropractic billing guide like this one.
If your practice is dealing with recurring chiropractic denials, or you want billing set up correctly from the start, Med Bridge LLC can help. Contact our team to learn how our medical billing and coding services can keep your chiropractic claims accurate and your reimbursements consistent.
