Take ACA's Quiz on Medicare Billing Modifiers

By Jaime Mulligan, Legal Affairs Manager; Bobby Gibson, Insurance Relations Operations Director; and Susan McClelland, ACA Medicare Committee Advisor


Editor’s Note: Readers, please note that this article is not intended for doctors of chiropractic participating in the Medicare Chiropractic Demonstration Project, which would include doctors in Maine, New Mexico, some parts of Illinois and Virginia, and Scott County in Iowa. Doctors from those areas who have chosen to participate in the project should consult www.acatoday.org/demo for the proper information and resources.  The information below will still be pertinent to doctors from those areas who are NOT participating in the demonstration project.


ACA receives a lot of questions about how and when to use Medicare modifiers. Knowing the answers to these questions requires some understanding of certain regulations and definitions. After reviewing the information that follows, take our quiz below to see if you can identify when specific modifiers should be used.


The first thing to understand is that, under Medicare, the only covered service for doctors of chiropractic is spinal manipulation—referred to in Medicare regulations as “manual manipulation of the spine to correct a subluxation.” Further, only active care (acute and chronic) is reimbursed.


Medicare does not reimburse maintenance care, although it is spinal manipulation and therefore still a “covered” service. (For the definitions of acute, chronic, and maintenance care, consult the Medicare section of the ACA’s Chiropractic Coding Solutions Manual or visit www.cms.hhs.gov/manuals/102_policy/bp102c15.pdf, Chapter 15 of the Medicare Benefit Policy Manual, §240.1.3.)


The critical thing to remember is that just because a service is “covered” does not necessarily mean that it is “reimbursable.”


This distinction is important for many reasons, but in this instance it is critical because it dictates the proper usage of the Medicare modifiers.


·        AT modifier: Active Treatment—used on covered services (spinal CMT) only. Active treatment consists of acute and chronic (active/corrective) care. The “AT” is required (as of Oct. 1, 2004) on active treatment 98940, 98941, and 98942, and it is meant to represent to Medicare that the care was medically necessary (under Medicare guidelines). The AT modifier would never be used for maintenance care. Make sure you understand the Medicare definitions of acute, chronic and maintenance care.


·        GA modifier: Advance Beneficiary Notice (ABN) on file—used on covered services (spinal CMT) only.  Use the ABN when you expect that a covered service (spinal manipulation) will be denied because of lack of medical necessity. If the treatment of a Medicare beneficiary is maintenance care—and therefore considered by Medicare to be not medically necessary and not reimbursable—you should ask the patient to sign an ABN, and you are required to append the “GA” modifier.


·        GZ modifier: Advance Beneficiary Notice (ABN) NOT on file—used on covered services (spinal CMT) only.  Use this modifier when an ABN should have been signed, but wasn’t. This modifier is a good-faith measure toward Medicare indicating that you recognize you made an error.  Please note that you may NOT collect payment from the patient.


·        GY modifier: Non-covered service (services that are statutorily excluded or do not meet the definition of any Medicare benefit)—used on all non-covered services (anything NOT spinal CMT).  This modifier is required on all services other than manual manipulation of the spine, including x-rays, extra-spinal CMT, therapy modalities and exams. Please note that you do not use “GY” on maintenance care spinal CMT.


·        GP modifier: Services delivered under an outpatient physical therapy plan of care—used on therapy services only.  This modifier is required on most therapy codes (consult the Medicare section of the ACA’s Chiropractic Coding Solutions for a complete list, or consult the Medicare FAQ at www.acatoday.org/government/medicare/reimbursement/medicare_faq.shtml#32). It would be used in addition to the GY modifier (e.g., 97035 GPGY). Please note, this does not mean therapy services are reimbursable if delivered by a doctor of chiropractic.


Jaime Mulligan can be reached at jmulligan@acatoday.org.


Medicare Modifier Quiz


1) You have treated a patient with maintenance care spinal CMT.  Is it reimbursable under Medicare?

a)      Yes

b)      No


2) You have treated a patient for maintenance care spinal CMT, and you know it isn’t reimbursable under Medicare. You also have a properly executed ABN on file. Which modifier(s) do you append to the code?

a)      –AT

b)      –GA

c)      –GZ


3) You have treated a patient for properly documented chronic care (hence, active) spinal CMT. Which modifier(s) do you append to the code, and is it reimbursable?

a)      –AT and yes

b)      –GA and yes

c)      –GY and no


4) You are billing Medicare for therapy services, which you know are statutorily excluded for doctors of chiropractic. Which modifier(s) do you append to the code?

a)      –GP

b)      –GY

c)      –GPGY



1) b

2) b

3) a

4) c