Blog Post

Crash-Course in Physical Therapy Billing Units

Here are the basics every PT should know about CPT code billing.

Erica McDermott
5 min read
April 12, 2021
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Physical therapy billing is complex. There’s a lot of nuance when it comes to not only determining the right PT billing units for a service, but also documenting to support those units—thus ensuring that you receive the payment you deserve. 

While PT billing is—and always will be—important, it’s especially crucial right now. Reimbursement rates are concerningly low, and the payment reductions just keep coming. Whether you’re a seasoned biller or brand new to the PT billing sphere, you’ll find value in our crash-course in PT billing units.

How to Select the Right Physical Therapy Billing Units

As Meredith Castin, PT, writes in this blog post, “Physical therapy billing is equal parts art and science.” In other words, there’s some creativity that goes into selecting the right PT billing units—as long as you ensure that “your CPT codes...always match the intent of the physical therapy interventions described in your notes.”

According to Castin, “that means that the more detailed your note, the more likely it is that you can bill a code with a higher reimbursement rate—because auditors will understand your therapeutic rationale.” And obviously, you want to maximize your payments. That said, “a detailed note alone does not always justify a higher-paying code.” There’s a fine line to walk, especially when it comes to codes where the therapeutic intent might not be so “cut and dried”—for example, when billing movement intervention codes like 97110, 97112, and 97530.

Check out Castin’s full post for example situations that warrant higher-paying codes. 

The CPT Code Basics

If you’re just getting started with PT billing codes, here are the CPT codes you should become most familiar with (as we originally outlined in this blog post):

  • Evaluations (97161-97163) and reevaluations (97164)
  • Supervised (un-timed) modalities (97010–97028)
  • Constant attendance (one-on-one) modalities (97032–97039) (billable in 15-minute increments)
  • Therapeutic (one-on-one) procedures (97110–97546)
  • Active wound care management (97597–97606)
  • Tests and measurements (97750–97755)
  • Orthotic and prosthetic management (97760–97762)

How to Calculate the Right Number of Units

CPT codes are either timed or untimed. As WebPT’s Brooke Andrus explains in this blog post, “For each untimed service you provided during a given date of service, you can bill one unit, regardless of how long you spent providing the service. Easy-peasy.” When it comes to timed codes, however, things can get a little confusing. Here’s what you need to know:

  • Each billable unit of an untimed code represents 15 minutes. If, for example, you perform 45 minutes of a particular service, then you could bill 3 units of that service (45 divided by 15 equals 3).
  • But what if you perform a service for a number of minutes that isn’t perfectly divisible by 15? You have to apply the 8-Minute Rule, which basically means that you must provide at least 8 minutes of a service to receive reimbursement for a full unit. 
  • The handy chart below will help you determine the maximum number of units you can bill for a particular date of service (note that you may not be able to bill the max number of units every time).
  • But what if, after performing all of your 8-Minute Rule calculations, you end up with a mixed remainder (that is, 8 minutes that represent two different services)? For example, let’s say you have 2 leftover minutes of manual therapy and 6 leftover minutes of therapeutic exercise. In this case, it’s important to know which version of the 8-Minute Rule the payer in question uses. Medicare and the American Medical Association (AMA) each define and apply the 8-Minute Rule differently—particularly with respect to mixed remainders. As explained in this blog post, under the Medicare rule, you can bill one unit of the service with the greatest time total (in our example, therapeutic exercise). Under the AMA’s rule, however, you cannot bill for any service unless you provided it for at least 8 minutes. In other words, mixed remainders don’t count. On first pass, it might sound like Medicare’s rule produces more favorable billing results—but that’s not always the case. Check out this blog post for an example.
  • Medicare’s 8-Minute Rule applies to all payers that receive federal funding (including Medicare, Tricare, and Medicaid). Commercial payers, on the other hand, can choose to use either rule. That means it’s up to you to know which rule each of your payers expects you to follow before you submit any claims. Otherwise, you risk claim denials.

How to Document to Support Your Billed Units

Ultimately, in order to support your billing, your documentation must clearly tell the story of your patient, your treatment, and your rationale for each intervention. This is the foundation of defensible documentation—that is, documentation that stands up to scrutiny. 

In short, if an auditor needs to review your notes, this person should easily be able to understand your patient’s health history and reason for seeking care—as well as what you did, why you did it, and how it worked. You’ll also want to be sure your notes clearly demonstrate that the skilled care of a physical therapist—as opposed to a lesser-trained practitioner—was required. No insurance company is going to pay a physical therapist for a service that could have been provided by, say, a personal trainer.

The Quick Checklist

Here’s a quick defensible documentation checklist (adapted from this Rehab Management article that we originally cited in this blog post):

Looking for an even more complete checklist? Download your free copy of the Defensible Documentation Toolkit. It comes with ten must-know defensible documentation tips, sample notes, and a handy checklist you can use to audit your notes.

There you have it: a crash course in PT billing units. If you’d like to go deeper into this subject, check out all of our PT billing blog posts.


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