The -GP modifier needs to be appended to physio-therapy codes when submitting Medicare claims. However, be aware of differing policies for different types of payers. Chiropractors typically use the following Physical Medicine codes from the CPT book: 97010 thru 97799 (except for 97597-97610 for active wound care management). The current descriptor for the -GP modifier is "services delivered under an outpatient physical therapy plan of care".  

Although non-covered, therapy services provided by a chiropractor must be submitted according to the therapy guidelines of the local Medicare Contractor. Local policies can vary. For example, PalmettoGBA states: 

"Because these services are excluded from coverage by law ('statutorily excluded' from coverage), chiropractors are not required to submit claims for therapy services to Palmetto GBA."

If a claim is submitted for therapy services, doctors of chiropractic must include the -GP modifier. Therapy services submitted without the appropriate modifier will be rejected as unprocessable.

The -GY modifier should also be used to indicate that the service is statutorily excluded. Furthermore, including therapy codes on claims for statistical purposes may be beneficial, which may impact future coverage determination.

Source:  PalmettoGBA, Jurisdiction 11, Part B, Chiropractic Services