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’s payment for rehab 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 as well as how it works in WebPT—followed by a comprehensive FAQ.

The 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 (extra emphasis on the word “Medicare” as this rule does not apply to other insurances unless they have specified that they follow Medicare billing guidelines). Basically, a therapist must provide direct, one-on-one therapy for at least eight minutes to receive reimbursement for 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—and therein lies the key to correctly applying this rule.

Time-Based Therapy vs. Service-Based Therapy

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 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 units you should bill, you should always start by calculating your total time (i.e., direct time + unattended time). Then, check your total against the chart below to see the maximum total number of codes you can bill:

8 – 22 minutes

1 unit

23 – 37 minutes

2 units

38 – 52 minutes

3 units

53 – 67 minutes

4 units

68 – 82 minutes

5 units

83 minutes

6 units

The key word here is “maximum.” There are times when you cannot bill the full number of units given in the chart. For example, let’s say that on a single date of service, you provide a patient with 30 minutes of therapeutic exercise, 15 minutes of manual therapy, 8 minutes of ultrasound, and 30 minutes of electrical stimulation (unattended). Per the 8-Minute Rule, you would first calculate the total treatment time: 30 min + 15 min + 8 min + 30 min = 83 total minutes

According to the chart, you could bill a maximum of 6 units. However, in this case, when adding up your direct time (time-based) codes, it equals 53 minutes. If you divide 53 by 15, you get 3 with a remainder of 8, which means you can bill 4 units of time-based codes. But because the untimed code accounts for the remaining 30 minutes of your total time—and you can only bill 1 unit for that an unattended modality regardless of how many minutes the patient spent receiving the service—you could not bill the full 6 units indicated in the chart above. Instead, you would bill 2 units of therapeutic exercise, 1 unit of manual therapy, 1 unit of ultrasound, and 1 unit of electrical stimulation (unattended), for a grand total of 5 units.

PT billing rules got you scratching your head? Download the PT’s Guide to Billing for a complete breakdown of everything you need to know to get paid.

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? Federally funded programs use the 8-Minute Rule. For others, 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 Rule of Eights 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 explains in this audio clip, 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 treatment time: 15+8+8+10 = 41 minutes. According to the chart above, the maximum total codes you can bill for 41 minutes is 3. Now, let’s take the total minutes of constant attendance services: 15+8+8 = 31. Then, divide that number by 15. You get two 15-minute services plus one extra minute. 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. In the comment section of this post, compliance expert Tom Ambury suggests “always choos[ing] the procedure that benefits the patient the most.” Then, you’d add one unit for untimed mechanical traction.

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?

As Lauren Milligan explains below, “If you’re dividing your attention among the patients—providing only brief, intermittent personal contact, or giving the same instructions to two or more patients at the same time—it’s appropriate to bill each patient one unit of 97150 regardless of time. Because group therapy is an untimed code, there is no specific minimum amount of time required to bill for it. 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?

All federally funded plans—including Medicare, Medicaid, TriCare, and CHAMPUS—require use of the 8-Minute Rule, as do some commercial payers. 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 SMP?

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.

How do the rules change if I’m only billing one service?

According to this BMS resource, “if you are providing only one service, you must get to 23 minutes before you bill for the second unit. For example, if you performed 9 minutes of therapeutic activities and 10 minutes of manual therapy, you would bill one unit each…even though the total is 19 minutes. But, if you performed 19 minutes of therapeutic exercises, you would bill only unit…” (As a side note, this holds true whether you’re using the SMP or 8-Minute Rule.)