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).

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 vs. Service-Based

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.

Mixed Remainders

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). However, it’s important to understand that there are insurers besides Medicare that have adopted the 8-Minute Rule, and not all of them follow Medicare’s billing guidelines. As this PT Compliance Group page points out, under the American Medical Association (AMA) billing guidelines, “there is no cumulative aspect to computing the correct charge.” In other words, per the AMA, 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.

To Bill or Not to Bill?

As if the whole mixed remainder thing weren’t enough to keep you on your toes, here’s one more Rule of Eights curve ball 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 jive, 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—about the 8-Minute Rule in general or how we handle it in WebPT—feel free to leave ’em in the comment section below. We’ll do our best to get you a response.

Triumph in the Triple-Aim Game: The Healthcare Executive’s Guide to Readmission Reduction, Patient Safety Promotion, and ACO Success - Regular BannerTriumph in the Triple-Aim Game: The Healthcare Executive’s Guide to Readmission Reduction, Patient Safety Promotion, and ACO Success - Small Banner
  • The Complete PT Billing FAQ Image

    articleMay 24, 2016 | 25 min. read

    The Complete PT Billing FAQ

    Over the years, WebPT has a hosted a slew of billing webinars and published dozens of billing-related blog posts. And in that time, we’ve received our fair share of tricky questions. Now, in an effort to satisfy your curiosity, we’ve compiled all of our most common brain-busters into one epic FAQ. Don’t see your question? Ask it in the comments below. Questions related to: • WebPT • Modifier 59 • Other Modifiers • Coding • ICD-10 • …

  • Can You Ace Our 8-Minute Rule Quiz? [Quiz] Image

    articleJul 21, 2015 | 1 min. read

    Can You Ace Our 8-Minute Rule Quiz? [Quiz]

    Maybe you thought your days of grinding through word problems ended when you sold that college algebra textbook back to the university bookstore (for less than half of its original price). But if you’re a rehab therapist who treats Medicare patients, you probably have to call upon your math skills—and maybe even the ol’ TI-83 Plus—fairly often, because sometimes Medicare’s 8-minute rule seems more like a complex trigonometric function than a seemingly straightforward billing formula. Think you’ve …

  • The 8-Minute Rule Showdown: Medicare vs. AMA Image

    articleNov 25, 2015 | 5 min. read

    The 8-Minute Rule Showdown: Medicare vs. AMA

    The guidelines for using the 8-Minute Rule are kind of like the instructions for building a piece of furniture from IKEA: they appear simple at first, but before you know it, you’ve been struggling for hours, you’ve got a lopsided futon, and there are seven leftover screws of various shapes and sizes scattered around your living room floor (maybe they’re just extras, right?). To make matters even more confusing, not all payers adhere to the same set …

  • A Tale of Two Billing Blunders: Overbilling and Misbilling Image

    articleJul 23, 2015 | 6 min. read

    A Tale of Two Billing Blunders: Overbilling and Misbilling

    Billing for physical therapy services is tricky, time-consuming, and nerve-wracking. After all, there are so many rules to follow, and it seems like those rules are constantly changing. That makes mistakes tough to avoid. And in many cases, you might not even know you’re making them. And while an occasional billing error probably isn’t a huge deal, if you’re unknowingly messing up left and right, you could end up in hot water. And if you’re purposely messing …

  • Pro-Bono Work: The Good, The Bad, and The Billing Image

    articleJul 20, 2015 | 7 min. read

    Pro-Bono Work: The Good, The Bad, and The Billing

    We’re all taught at a young age that it’s better to give than to receive. This saying helps children develop perspective, and even as adults, few people would argue against the moral truth of this simple axiom. In fact, I’m betting this statement really speaks to the empathetic nature of rehab therapists. Unfortunately, though, when you’re running a business (for the purposes of this blog, I’m referring to a private practice outpatient therapy clinic), you really need …

  • articleMar 20, 2013 | 5 min. read

    “What Box Does my G-Code Go Into?”: Responding to Outdated Questions Related to Paper Billing Claims

    Today’s blog comes from WebPT’s Billing Onboarding & Operations Manager Stacey Abelman. Thanks Stacey!   Members often ask: where does my G-code go? Or what box does my NPI go into? Additionally, we—as the WebPT Billing Service—receive such requests as “I need my facility address changed in Box 32” or “I need to use my Tax ID instead of my SSN in box 24j.” But these “boxes” that Members sometimes refer to don't exist anymore in modern …

  • Dual-Coding Wonder Twin Powers: Activate? Image

    articleSep 2, 2015 | 3 min. read

    Dual-Coding Wonder Twin Powers: Activate?

    Thirty days has September—and so has your clinic to prepare for ICD-10. Just one month from now, you’ll have to start using ICD-10 codes on most claims with dates of service on or after October 1, 2015. Did you see I wrote, “most”? That’s not a typo. The reason I can’t say “all” is because not all payers are switching to ICD-10. That means you’ll have to be bi-code-lingual (so don’t purge your brain of all ICD-9 …

  • Technical Diligence: The Key to Stopping Claim Denials Dead in their Tracks Image

    articleJul 9, 2015 | 5 min. read

    Technical Diligence: The Key to Stopping Claim Denials Dead in their Tracks

    Hello, readers. Over the past several weeks, I’ve enjoyed answering a number of your questions regarding billing for PT services, so I’m excited to address the topic right here on the WebPT Blog. On June 19, 2015, the Office of the Inspector General (OIG) released a report involving an outpatient private practice physical therapy provider. In case you weren’t aware, the OIG—which is part of the US Department of Health and Human Services (HHS)—is basically the CMS …

  • The PT’s Guide to Surviving a Medicare Audit Image

    articleMay 30, 2016 | 5 min. read

    The PT’s Guide to Surviving a Medicare Audit

    “How can I avoid being audited by Medicare?” This is one of the compliance questions I hear most frequently, and the honest answer is, quite simply, that you can’t. Just because CMS or one of its auditing entities hasn’t come knocking on your door doesn’t mean you’re not being audited. In fact, every claim you submit undergoes statistical analysis, and Medicare compares your claims data to the data for all other claims submitted. Furthermore, Medicare now analyzes …

Achieve greatness in practice with the ultimate EMR for PTs, OTs, and SLPs.