Modifier GP: Physical Therapy Plan of Care
The GP modifier marks services delivered under an outpatient physical therapy plan of care. Who must use GP, how it pairs with CQ and KX, and GP vs GO vs GN.
Modifier GP is a HCPCS Level II modifier that identifies a service delivered under an outpatient physical therapy plan of care. CMS's descriptor is "Services delivered under an outpatient physical therapy plan of care" (Pub. 100-04, ch. 5, §20.1). Medicare requires GP, GO or GN on every therapy code, and returns claims for "always therapy" codes that arrive without one.
Key takeaways
- GP is required on physical therapy codes such as 97110, 97140 and 97530, whoever bills them: therapists, physicians, NPPs, hospitals, SNFs and CORFs.
- Use exactly one discipline modifier per line: GP for PT, GO for OT, GN for speech-language pathology.
- GP doesn't change the rate. It tells Medicare to count the service toward the yearly therapy threshold.
- Services by a physical therapist assistant add CQ next to GP. Medicare's payment drops 15%; the allowed amount doesn't change.
- Above the yearly threshold, medically necessary therapy also needs KX.
Modifier GP · payment effect
With and without the modifier
97110 without GP · national office
$29.06
Therapeutic exercise
97110-GP · No change to the rate
$29.06
Delivered under a physical therapy plan of care. Required on therapy codes; no rate change.
When to use the GP modifier
Add GP to a line when:
- The code is on CMS's list of therapy services and the service was furnished under a physical therapy plan of care. Evaluations (97161–97163), therapeutic exercise, manual therapy, neuromuscular re-education (97112), gait training (97116) and therapeutic activities are the everyday examples.
- The code is an "always therapy" code: it needs a therapy modifier no matter who bills it. Claims without one are returned (CARC 4).
- The code is a "sometimes therapy" code furnished by a therapist or under a therapy plan of care. A physician or NPP may bill those codes without a therapy modifier only when the service isn't therapy.
- A non-listed code is furnished by a therapist as part of the PT plan of care. CMS's example is casting and strapping codes (29000–29590) applied by a therapist.
The same rule applies on institutional claims: revenue code 42x (physical therapy) lines may carry only GP, and PT evaluation codes must always carry GP (ch. 5, §20.1).
8-minute rule
Timed minutes → billable units
Medicare: 41 timed minutes
3 units
97110 × 2 · 97140 × 1 · about $85.84 nationally before therapy reductions
- Per-code method
- 4 units
- Difference
- +1
| Code | Minutes | Full 15-min units | Leftover min | Medicare units | Per-code units |
|---|---|---|---|---|---|
| 97110 | 23 | 1 | 8 | 2 ● | 2 |
| 97140 | 10 | 0 | 10 | 1 ● | 1 |
| 97530 | 8 | 0 | 8 | 0 | 1 |
● Extra unit assigned from leftover minutes, to the code with the most leftover time.
When not to use the GP modifier
- Occupational therapy plans of care use GO; speech-language pathology uses GN.
- Codes not on the therapy list that aren't part of a therapy plan, such as respiratory therapy or nutrition services.
- Diagnostic codes CMS names as non-therapy, such as nerve conduction and EMG codes (95860–95934 range listed in ch. 5, §20), even when a therapist performs them.
- Respiratory G-codes G0237–G0239, which are billed without therapy modifiers unless a PT or OT uses the 97000-series instead.
How GP affects payment
GP carries no percentage. Physical therapy codes are paid from the physician fee schedule with or without it; its jobs are routing and tracking:
- Therapy threshold. Medicare's claims system applies the yearly therapy amount to every service billed with GN, GO or GP. PT and speech-language pathology share one threshold; above it, medically necessary services need KX.
- Assistant services. When a physical therapist assistant furnishes a service in whole or in part, add CQ alongside GP. CQ must be paired with GP or the claim is returned. Since January 1, 2022 Medicare reduces its payment for those services by 15%. The allowed amount and the patient's 20% coinsurance stay the same; the cut comes off Medicare's share, after the multiple procedure payment reduction (ch. 5, §20; Transmittal R11129CP).
- Multiple procedure reduction. Therapy practice expense is reduced for the second and later units in a day; see the therapy MPPR calculator.
Units for timed codes follow the CMS 8-minute rule; the 8-minute rule calculator does the math per code.
GP vs GO, GN, CQ and KX
FAQ
What is the GP modifier for?
It tells Medicare that a service was delivered under an outpatient physical therapy plan of care. It's required on PT services so Medicare can identify them and apply the therapy threshold.
What is billing code 97110 with the GP modifier?
Therapeutic exercise, billed per 15 minutes, furnished under a physical therapy plan of care. 97110 is an "always therapy" code, so Medicare returns it without GP, GO or GN.
What is the difference between the GO and GP modifiers?
GP is for services under a physical therapy plan of care; GO is for services under an occupational therapy plan of care. The same code, such as 97530, takes whichever matches the plan.
What does modifier 59 with GP mean?
Both can be on one line. GP identifies the plan of care, and 59 bypasses an NCCI edit between two therapy codes done in separate time blocks, such as 97530 and 97140.
Do physicians need the GP modifier?
Yes, for "always therapy" codes and for "sometimes therapy" codes when the service is therapy. Physicians and NPPs who furnish therapy follow the same modifier rules as therapists.
Keep reading
- 8-minute rule calculator for units of timed PT codes.
- Modifier KX for therapy above the yearly threshold.
- Modifier 59 for NCCI pairs between therapy codes.
- Codes on this page: 97110 97140 97530 97112 97116 97161
Sources: CMS Medicare Claims Processing Manual, Pub. 100-04, ch. 5, §§10.3.1, 10.4, 20 and 20.1. Verified October 6, 2026.
