The 8-minute rule for physical therapy, straight from CMS

Thirty-three minutes of therapeutic exercise and seven minutes of manual therapy. Medicare’s manual bills that visit as three units. The convention printed in the CPT book bills it as two. Same patient, same 40 minutes, same note. The only thing that changed is which payer is reading the claim.

The rule gets paraphrased far more often than it gets read. The source is a couple of pages of the Medicare Claims Processing Manual, and its worked examples are better than the paraphrases. Here is what those pages say, what the payers that copied them say, and what a unit is worth this year.

What is the 8-minute rule?

The 8-minute rule is Medicare’s method for converting treatment minutes into billable units of 15-minute timed CPT codes. Under the Medicare Claims Processing Manual, chapter 5, 8 through 22 minutes of a timed service bills one unit and 23 through 37 bills two. Each further unit needs another 15 minutes. A timed code that was the only service that day and ran under 8 minutes is not billable.

The manual adds that “the pattern remains the same for treatment times in excess of 2 hours.” The section’s current revision took effect on January 1, 2017.

The chart covers codes written in 15-minute units: 97110, 97112, 97116, 97140, 97530 and their neighbors. Untimed codes bill one unit however long they take. CMS’s outpatient rehabilitation documentation fact sheet names the evaluations, group therapy and supervised modalities as untimed, and says not to count their minutes toward the timed codes.

How does Medicare count minutes across several codes?

Medicare adds up every timed minute in the visit first, reads the total against the chart, and only then assigns units to codes. In the manual’s words, the number of timed units “is constrained by the total treatment minutes for that day.”

The worked examples are the part most guides skip. Thirty-three minutes of 97110 and seven of 97140 total 40 minutes, which is three units. “Count the first 30 minutes of 97110 as two full units,” the manual says. Then compare the leftover three minutes of exercise to the seven of manual therapy and bill the larger. One unit goes to a code that never reached eight minutes on its own.

The constraint cuts both ways. Eighteen minutes of exercise, 13 of manual therapy, 10 of gait training and 8 of ultrasound total 49 minutes: three units, and the ultrasound goes unbilled. “You would still document the ultrasound in the treatment notes.” The fact sheet states the trap plainly: four distinct, separate 8-minute treatments are 32 minutes, and “you may report only 2 units.” Every timed minute still counts toward the total, though; the chart “does not imply that any minute until the eighth should be excluded from the total count.”

Then the sentence underneath the chart. “The expectation (based on the work values for these codes) is that a provider’s direct patient contact time for each unit will average 15 minutes in length. If a provider has a consistent practice of billing less than 15 minutes for a unit, these situations should be highlighted for review.” CMS’s Part B billing scenarios for PTs and OTs run that arithmetic on six patients treated one-on-one for 10 minutes each in an hour. Routine billing of that pattern “would likely cause the contractor to question whether the services were reasonable and necessary.”

What counts as treatment time?

Treatment time is the minutes the patient is being treated, and nothing around them. The manual says the clock starts when the therapist, or an assistant under supervision, is directly working with the patient. The patient “should already be in the treatment area.” Pre- and post-delivery time does not count. Toileting, resting and waiting for a piece of equipment do not count.

The billing scenarios draw the line on the gym floor. Supervising a patient who is exercising independently “is not a skilled service” and cannot be billed. One-on-one minutes can be split across the visit, “10 minutes now, 5 minutes later.” A therapist moving between two patients “spending a minute or two at a time” is providing group therapy: one untimed unit of 97150 each.

8-minute rule vs rule of eights: which payers use which?

The CPT manual’s convention bills a unit of a 15-minute code once that code passes its midpoint, code by code, with no daily total. Medicare’s rule totals the day first. Commercial payers pick one and put the choice in a reimbursement policy.

APTA’s coding guidance for timed codes puts the CPT threshold at “7 minutes and 31 seconds.” It notes that the CPT guidelines “do not indicate a requirement to add total minutes to determine how many units can be billed.” That single difference moves the count both ways. The 33-plus-7 visit is three Medicare units and two CPT units, because seven minutes of manual therapy never passes a midpoint of its own. Flip the visit to 10 minutes each of three different codes and CPT bills three units where Medicare’s 30-minute total allows two.

The label a payer uses tells you nothing about which math it runs. Anthem’s commercial reimbursement policy C-07002, last approved August 13, 2025, reproduces Medicare’s chart and its aggregation rule nearly word for word. Its policy history shows it was retitled “Rule of Eight” in December 2009.

UnitedHealthcare’s commercial policy 2026R0101A says that “in alignment with” CMS, at least eight minutes must be performed to bill one 15-minute unit. Then it adds a limit Medicare does not have. It reimburses the listed timed codes “up to a maximum of four timed codes (equivalent to one hour of therapy) per date of service” per specialty. Anything beyond that goes to a reconsideration request. 97110, 97112, 97140 and 97530 are all on the list.

APTA’s advice is to bill every payer consistently and read each policy anyway; a contract clause outranks both conventions.

What is one unit worth in 2026?

One unit of 97110 carries 0.87 total relative value units in CMS’s 2026 PFS relative value file, and the 2026 conversion factor is $33.4009. That puts the national amount for a unit of therapeutic exercise at $29.06. It is before the geographic index and the therapy multiple-procedure reduction, a 50% cut to the practice-expense portion on flagged codes, 97110 included.

The untimed evaluation codes 97161 through 97163 all carry 2.93 RVUs, or $97.86, whatever their complexity level. Hot and cold packs, 97010, are a bundled code: Medicare pays nothing separately.

A visit documented at 52 timed minutes is three units. One more minute of skilled, documented treatment is a fourth, worth $27.72 to $35.07 for the codes in the table.

The rate itself dodged a cut this year. The CY 2026 fee schedule final rule applies a new 2.5% efficiency adjustment to work RVUs and exempts time-based codes from it. Commenters pointed out that CMS’s proposed list had swept in physical medicine and rehabilitation codes regardless. CMS agreed and “removed the time-based physical medicine and rehabilitation services and RTM services” from the list.

What has to be in the note?

Medicare requires two totals on every treatment note. The Medicare Benefit Policy Manual, chapter 15 requires “total timed code treatment minutes and total treatment time in minutes,” where total treatment time includes untimed codes and excludes rest periods. Minutes per intervention “may also be recorded voluntarily, but contractors shall not require it.” Then the sentence that decides reviews: “The billing and the total timed code treatment minutes must be consistent.”

CMS’s fact sheet lists “missing total time” in its table of common CERT errors. Anthem asks for the same two totals. A Medicare reviewer needs no clinical judgment to cite a note that shows 52 timed minutes under four units; the arithmetic does it.

Arithmetic is cheapest while the patient is still on the table. Aurora, the ambient AI scribe included in both Orion plans, drafts the PT-specific note while you treat. Focus on your patient, not your keyboard. A timed code missing its minutes surfaces in the visit, while the clinician is still in the room. The claim scrub in Orion’s billing then checks units against documented treatment time before anything leaves the practice.

The number of units was never a judgment call. It is the total minutes, read against a chart, written in the note. Write both totals and count them, and the 8-minute rule becomes something you can show a reviewer.