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 of 8-Minute Rule guidelines. While the Medicare 8-Minute Rule is probably the most-referenced version of this method for calculating billable units, we can’t forget about its less-famous sibling, the American Medical Association (AMA) 8-Minute Rule. After all, the AMA is technically the ruler of all things Current Procedural Terminology (CPT), and that’s just what the 8-Minute Rule is for: calculating the proper number of CPT code units to bill for a particular encounter. So, how do these two 8-Minute Rule variations differ? Here’s the breakdown:

The Medicare 8-Minute Rule

As compliance expert Tom Ambury explains in this PT Compliance Group blog post, this version of the rule applies “to all insurances that accept Federal funding, i.e. Medicare, Medicaid, Medicare Advantage Plans, TriCare, CHAMPUS, etc.” When billing for services provided to patients with these insurances, you must distinguish between timed (a.k.a. constant attendance) codes and untimed (a.k.a. service-based) codes. (The CPT code book designates each CPT code as either timed or untimed.)

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. But, when it comes to calculating units for timed services, things get a little more complicated. Each billed unit of a timed code represents 15 minutes. To give a simple example, if you provided 30 minutes of manual therapy—which is represented by the time-based CPT code 97140—you could bill for two units.  

But as every rehab therapist knows, services aren’t always provided in perfect 15-minute increments. What, then, is the threshold for billing a full unit? That’s where the 8-Minute Rule comes in. Here’s the main premise of the rule, as explained in this blog post: “Basically, a therapist must provide direct, one-on-one therapy for at least eight minutes to receive reimbursement for a time-based treatment code.”

So, if you provided 35 minutes of manual therapy, you still could only bill for two units, because when you divide 35 by 15, you get 2 with a remainder of 5. That remainder does not meet the 8-minute threshold for billing an additional unit. If, instead, you had provided 38 minutes of of manual therapy, you would be able to bill three units because your remainder of 8 would justify billing an additional unit.

You can get a full run-down of how the 8-Minute Rule works here, but for the sake of space, I’ll jump straight to the handy-dandy chart most therapists use to determine how many timed units they can bill for a particular date of service:

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

In this chart, the quantity of time in the left column represents the total timed minutes, and the quantity in the right column represents the associated maximum number of units you can bill based on the time total. Now, there are plenty of tricky scenarios that could trip up your calculation efforts—some of which are presented in this 8-Minute Rule quiz—but for the most part, this chart is pretty accurate.

And now we’ve come to the detail that might put a little hitch in your 8-Minute Rule get-along: mixed remainders. What do I mean by that? Well, sometimes, when you divide the total timed minutes by 15, you get a remainder that represents more than one service. For example, you might have 3 leftover minutes of therapeutic exercise and 5 leftover minutes of manual therapy. When each of these remainders stands on its own, neither meets the 8-minute threshold. However, when combined, they equal 8 minutes—and according to Medicare’s billing guidelines, that means you can bill one unit of the service with the greatest time total (in this case, manual therapy).

The AMA 8-Minute Rule Variation

This is precisely where Medicare and the AMA diverge: per AMA 8-Minute Rule guidelines, you cannot use the cumulative total of your remainders to justify billing additional units. In other words, as explained here, “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.” So, in the example above, you could not bill for any additional units, because neither the 3 minutes of therapeutic exercise nor the 5 minutes of manual therapy meets the 8-minute threshold.

Got it? Great. If not, check out these exercises to get yourself in rockin’ good 8-Minute Rule shape. In the meantime, I’m gonna go kick it on my rockin’ (literally) good futon.