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What is the 8-Minute Rule? (And Other Frequently Asked Questions)

Medicare’s payment rules for PT services aren’t always so simple. Here's a rundown of the 8-minute rule as well as how it works in WebPT.

Erica McDermott
5 min read
September 13, 2018
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With most buyer-seller transactions, calculating the cost of a product or service is fairly simple. There are no complicated formulas for determining the monetary value of a pizza or a movie ticket; you simply pay the business’s advertised price. When it comes to Medicare units and payment for physical therapy services, however, things aren’t always so simple. Yes, I’m talking about the dreaded 8-Minute Rule (a.k.a. the Rule of Eights). So, here’s a rundown of the rule—and a short explanation of how it works in WebPT.

8-Minute Rule Basics

The 8-Minute Rule governs the process by which rehab therapists determine how many units they should bill to Medicare for the outpatient therapy services they provide on a particular date of service. (This rule also applies to other insurances that have specified they follow Medicare billing guidelines.) Basically, a therapist must provide direct, one-on-one therapy for at least eight minutes to receive reimbursement for one unit of a time-based treatment code. It might sound simple enough, but things get a little hairy when you bill both time-based and service-based codes for a single patient visit.

Time-Based Units vs. Service-Based Units

So first, let’s talk about the difference between time-based and service-based CPT codes. You would use a service-based (or untimed) code to denote services such as conducting a physical therapy examination or re-examination, applying hot or cold packs, or providing electrical stimulation (unattended). For services like these, you can’t bill more than one unit—regardless of the amount of time you spend delivering treatment.

Time-based (or direct time) codes, on the other hand, allow you to bill multiple units in 15-minute increments (i.e., one unit = 15 minutes of direct therapy). These are the codes you use for one-on-one, constant attendance procedures and modalities such as therapeutic exercise or activities, manual therapy, neuromuscular re-education, gait training, ultrasound, iontophoresis, or electrical stimulation (attended).

Minutes and Billing Units

According to CPT guidelines, each timed code represents 15 minutes of treatment. But your treatment time for these codes won’t always divide into perfect 15-minute blocks. What if you only provide ultrasound for 11 minutes? Or manual therapy for 6 minutes? That’s where the 8-Minute Rule comes in: Per Medicare rules, in order to bill one unit of a timed CPT code, you must perform the associated modality for at least 8 minutes. In other words, Medicare adds up the total minutes of skilled, one-on-one therapy (direct time) and divides the resulting sum by 15. If eight or more minutes are left over, you can bill for an additional unit. But if seven or fewer minutes remain, Medicare will not reimburse you for another full unit, and you must essentially drop the remainder. To give a simple example, if you performed manual therapy for 15 minutes and ultrasound for 8 minutes, you could bill two direct time units.

However, when untimed codes come into play, things get a little more confusing. So, to figure out how many total billing units you have, you should always start by adding up your one-on-one time (leave unattended time out of the equation). Then, check your total against the chart below to see the maximum total number of codes you can bill:

Mixed Reminders

What if, when you divide your direct time minutes by 15, your remainder represents a combination of leftover minutes from more than one service (for example, 5 minutes of manual therapy and 3 minutes of ultrasound)? Do you bill for one service, all of the services, or none of them? The answer depends on the billing guidelines you’re using. Per Medicare, as long as the sum of your remainders is at least eight minutes, you should bill for the individual service with the biggest time total, even if that total is less than eight minutes on its own. (In the example above, you would bill 1 additional unit of manual therapy).

Non-Medicare Insurances

However, it’s important to understand that there are insurers who don’t require providers to adhere to the 8-Minute Rule. As this resource points out, under the Substantial Portion Methodology (SPM), there is no cumulation of minutes or remainders; in order to charge for a unit of service, you must have performed that service for a “substantial portion” of 15 minutes (i.e., at least 8 minutes). That means that if your leftover minutes come from a combination of services, you cannot bill for any of them unless one individual service totals at least eight minutes.

However, in some cases, using SPM may actually enable you to bill for more units than the 8-Minute Rule does. As the example in the above-cited resource demonstrates, if you perform 10 minutes of manual therapy and 8 minutes of therapeutic exercise on a patient, you can bill 1 unit of manual therapy under the 8-Minute Rule and 1 unit of manual therapy plus 1 unit of therapeutic exercise under SPM. But, how do you know which billing methodology a particular payer uses? Your best bet is to ask. If the insurance company doesn’t have a preference, you may want to calculate your units using both methods to determine which will better serve your practice.

To Bill or Not to Bill?

Now, back to 8-Minute Rule math. As if the whole mixed remainder thing weren’t enough to keep you on your toes, here’s one more curveball for you: in some cases, you probably shouldn’t bill any units for a service, even though you provided it. Take iontophoresis, for example. As insurance billing expert Rick Gawenda has explained, a patient undergoing iontophoresis might only receive direct, skilled treatment from the therapist for two or three minutes; the rest of the time (once the machine is turned on) is not billable because Medicare doesn’t consider it “skilled time.” (As a side note, checking the patient’s skin for damage upon electrode removal would be considered skilled therapy, making it billable time. But it is unlikely that this time would be enough to put you over the 8-minute threshold.) Thus, according to the 8-Minute Rule, the therapist in this scenario wouldn’t be able to bill any units for that particular treatment.

The 8-Minute Rule in WebPT

If all this talk about quotients and remainders is triggering flashbacks to fifth-grade math—yikes, long division!—don’t worry. WebPT automatically double-checks your work for you and alerts you if something doesn’t add up correctly. All you have to do is record the time you spend on each modality as you go through your normal documentation process, along with the number of units you wish to bill. If those two totals don’t jibe, WebPT will not only let you know something’s off, but we’ll also tell you whether you overbilled or underbilled. That way, you can quickly identify and fix the problem—and thus, ensure accurate payment. Plus, you’ll have a detailed record of the services you provided on each date of service—something many local MAC auditors request to substantiate billing claims and processes.

That wasn’t so bad, right? If you still have questions, keep reading. We’ve compiled a list of the most frequently asked 8-Minute Rule questions—and their answers. Don’t see the answer you’re looking for? Leave us your question in the comment section at the bottom of this post.

8-Minute Rule FAQ

What is the 8-Minute Rule?

Put simply, to receive payment from Medicare for a time-based (or constant attendance) CPT code, a therapist must provide direct treatment for at least eight minutes. To calculate the number of billable units for a date of service, providers must add up the total minutes of skilled, one-on-one therapy and divide that total by 15. If eight or more minutes remain, you can bill one more unit. Otherwise, you cannot.

What are time-based CPT codes?

Time-based (or constant attendance) codes allow for variable billing in 15-minute increments. These differ from service-based (or untimed) codes, which providers can only bill once regardless of how long they spend providing a particular treatment.

Per the 8-Minute Rule, if a therapist provides 15 minutes of therapeutic exercise, 8 minutes of gait training, 8 minutes of manual therapy, and 10 minutes of mechanical traction, what would be appropriate to bill?

To start, let’s add up the total one-on-one treatment time. Since mechanical traction is an untimed service, you would add up the 15 minutes of therapeutic exercise, 8 minutes of gait training and 8 minutes of manual therapy for a total of 31 minutes. According to the chart above, the maximum total codes you can bill for 31 minutes is 2. So, you’d bill one unit of therapeutic exercise plus one unit of either gait training or manual therapy. Because you performed those services for the same amount of time, you can choose either—though we recommend choosing the service your patient benefited from the most. Then, you’d add one unit for untimed mechanical traction for a total of 3 billable units.

What is a mixed remainder?

A mixed remainder is a combination of leftover minutes from more than one service after you have calculated the total number of full units you can bill. For example, if you provided 20 minutes of manual therapy and 18 minutes of ultrasound, you can bill one full unit of each with 5 minutes of manual therapy and 3 minutes of ultrasound leftover. While the rules around billing for leftover minutes differ according to payer, for Medicare, as long as the sum of your remainders is at least eight minutes, you should bill for the individual service with the biggest time total—even if that total is less than eight minutes on its own. So, in the aforementioned example, you would bill 1 additional unit of manual therapy.

Does the number of hours a therapist works per day—or the number of patients a therapist sees per day—factor into the 8-Minute Rule billing requirements?

As Brooke Andrus explains in the comment section, “The 8-minute rule does not account for the number of hours a therapist works per day or the number of patients that therapist treats during the day. All that matters is the number of minutes the therapist spent providing each billed service.”

Does the 8-Minute Rule apply to Medicare Part A services?

No; the 8-Minute Rule only applies to Medicare Part B services.

Does the 8-Minute Rule apply to group therapy codes?

Sort of. Because group therapy is an untimed code, there is no specific minimum amount of time required to bill for it, and every patient can be billed for one unit of 97150. However, Medicare advises that group therapy sessions should be “of sufficient length to address the needs of each of the patients in the group.”

What insurance companies require providers to adhere to the 8-Minute Rule?

The 8-Minute Rule applies to Medicare in addition to a swathe of other plans (including some that fall under federal, state, and commercial purview). That said, to determine the requirements for individual payers, it’s best to contact the payer directly.

Which billing method is better—the 8-Minute Rule or SPM?

It depends. Obviously, for Medicare and other payers that require the 8-Minute Rule, providers don’t have a choice as to which billing method to use. For commercial payers that don’t have a requirement, providers may want to complete both calculations to see which method produces the best results. According to this resource, “only one billing method can be used per individual treatment session.” When in doubt, always contact the payer to learn more about its specific billing requirements.


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