Blog Post

4 Common Physical Therapy Billing Modifiers (and How to Use Them)

Modifiers help ensure you receive the appropriate amount of reimbursement for your physical therapy services—if you follow these rules.

Meredith Castin
5 min read
July 6, 2018
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Physical therapists (PTs) enjoy being part of a profession known for compassion. The vast majority of PTs enter the field eager to help patients achieve their full functional abilities. That said, a PT clinic is still a business, and if you aren’t billing properly, it’s hard to keep your clinic afloat so you can improve the lives of the very patients you set out to help.

Luckily, there are plenty of ways to bill in a way that’s both conscientious and favorable to keeping your financials thriving. In some cases, this will involve the use of modifiers, which provide additional information when diagnosis and procedure codes are not sufficient for payers to process and reimburse claims.

What Types of Physical Therapy Billing Modifiers are there?

There are two overarching categories of PT billing modifiers:

  • CPT modifiers: These are two-digit codes that apply to CPT codes.
  • Level II HCPCS (Healthcare Common Procedure Coding System) modifiers: These are two-letter codes used by Medicare as well as some Medicaid and commercial plans.

Here are four common PT billing modifiers, as well as some ways you can use them to bill appropriately for your organization:

CPT Modifiers

59 modifier

The 59 modifier signifies to Medicare that you performed a service or procedure separately and distinctly from another non-evaluation and management service provided on the same day. It’s a way to tell Medicare that payment for both services complies with the National Correct Coding Initiative. You can also use this modifier when you perform a procedure on a separate and distinct body part. (Note: There are subsets of the 59 modifier, including XE, XS, XP, and XU, which you can learn more about in this blog post.)


  1. You’re treating a patient with an ankle sprain, and you’re billing 15 minutes of manual therapy (CPT code 97140) and 15 minutes of therapeutic activity (CPT code 97530) on the same date of service. Add the 59 modifier to code 97530, and it allows you to receive payment for both of these timed codes (provided you performed them during separate 15-minute increments).
  2. You are providing therapeutic exercise services to a patient, but you note she is not making progress and opt to perform a re-evaluation during the same visit to update the plan of care. The 59 modifier allows you to bill for both the re-evaluation and the therapeutic exercise.

Still unsure when to apply the 59 modifier? Check out this decision chart.

Level II HCPCS (Healthcare Common Procedure Coding System) Modifiers  

GP modifier

What is a GP modifier? The GP modifier indicates that a physical therapist’s services have been provided. It’s commonly used in inpatient and outpatient multidisciplinary settings. It’s also used for functional limitation reporting (FLR), as physical therapists must report G-codes, severity modifiers, and therapy modifiers. Be aware that some payers require use of a therapy modifier when billing for a designated therapy code.


Use a GP modifier in any case where there could be confusion as to which provider delivered services to a patient, such as in any interdisciplinary therapy setting.

KX modifier

This modifier is used for services provided after a patient exceeds Medicare’s $2,010 threshold. Be sure that you only use this modifier when you know that continued treatment is medically necessary and must be performed by a therapist—and that you justify that necessity with appropriate documentation in the patient’s medical record.

Note: If you realize a patient will need this code, start documenting the reasons why as soon as possible. However, do not apply the code until it’s necessary to do so, as this could throw up a red flag to Medicare, thus making your clinic more vulnerable to an audit.


A patient was treated for a hip fracture early in the year and hit the $2,010 threshold. But later in the year, he has a cerebrovascular accident and requires therapy beyond that threshold, so the therapist applies a KX modifier to justify continued care.  

GA modifier

This modifier indicates that a required Advance Beneficiary Notice of Noncoverage (ABN) is on file for a service not considered medically necessary. It allows the provider to bill a secondary insurance for non-Medicare-covered services, and it also allows the provider to bill the patient directly. When you submit a claim containing this modifier, you should anticipate that Medicare will use claim readjustment reason code 50.


You’ve been seeing a Medicare patient for six weeks for post-op services, but the patient has now reached a functional plateau. However, she still wishes to attend PT for maintenance and to maintain accountability. You can use the GA modifier to either continue billing secondary insurances, or bill the patient directly.


We're often challenged by the level of payment for our services. That's why it's so important to remember that modifiers exist to help us bill appropriately for the time we spend with patients—and they help ensure we receive payment for the services we provide. That said, as compliance expert Tom Ambury has pointed out, we never want to use a billing modifier on a claim simply because we feel we may receive more payment. Our documentation must always support what we bill, and what we bill must always reflect medically necessary and skilled care.

Still feeling mixed up about modifiers? See how WebPT's array of compliance tools can simplify modifier usage and more.


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