The Medicare 8-Minute Rule: A Complete Guide for Therapists
The 8-minute rule is how Medicare Part B converts the minutes of skilled therapy you deliver into the units you’re allowed to bill for time-based CPT codes. It sounds simple: 8 minutes gets you a unit. But the actual mechanics involve a total-time constraint, remainder allocation across codes, and a set of exclusions that generate a steady stream of denials and downcodes for practices that get them wrong.
This guide works from the primary source: the Medicare Claims Processing Manual, Chapter 5, §20.2–20.3 (Pub. 100-04), including CMS’s own worked examples. Where a number can change year to year, it’s dated. All figures are current as of August 2026.
The unit chart
For any single calendar day, total your minutes of timed-code treatment and read the billable units off this chart (Medicare Claims Processing Manual, Ch. 5, §20.2.C):
| Units | Total timed minutes |
|---|---|
| 1 | 8 – 22 |
| 2 | 23 – 37 |
| 3 | 38 – 52 |
| 4 | 53 – 67 |
| 5 | 68 – 82 |
| 6 | 83 – 97 |
| 7 | 98 – 112 |
| 8 | 113 – 127 |
The pattern continues past two hours: the minimum for n units is (15 × n) − 7 minutes. If only one service is provided in a day and it ran fewer than 8 minutes, it isn’t billable at all.
The rule only applies to timed codes
CPT codes for therapy fall into two groups, and only one of them uses the chart:
Timed codes (billed in 15-minute units of direct, one-on-one treatment) include the codes outpatient rehab bills most: therapeutic exercise (97110), neuromuscular re-education (97112), gait training (97116), manual therapy (97140), therapeutic activities (97530), self-care/home management training (97535), and attended modalities like ultrasound (97035).
Untimed codes are billed as one unit per session regardless of duration. That includes evaluations and re-evaluations (97161–97164 for PT), unattended electrical stimulation (G0283), and hot/cold packs (97010). Their minutes never enter the unit chart: a 45-minute evaluation is still one unit of the evaluation code and zero timed minutes.
Mixing these up in either direction is a common error. Counting eval minutes toward timed units inflates the claim; forgetting that attended modalities are timed leaves units unbilled.
What time actually counts
Manual §20.3 defines countable time as intra-service care: the clock starts when the therapist (or an assistant under supervision) is directly working with the patient, who is already in the treatment area and prepared to begin. Specifically excluded:
- Pre- and post-delivery services (setup before the patient is ready, cleanup, documentation time)
- Time the patient spends resting or toileting
- Time waiting for equipment or for another treatment to begin
Two details from this section that surprise people:
- Two clinicians don’t double the time. If gait training requires both a therapist and an assistant to manage a patient in the parallel bars, each 15 minutes of treatment still counts as only one unit of 97116. Time is counted per patient, not per provider.
- Minutes under 8 still count toward the total. The manual is explicit that the schedule “does not imply that any minute until the eighth should be excluded from the total count.” A 7-minute service isn’t billable on its own, but its minutes are still added to the day’s total timed minutes. That is exactly how mixed remainders work, below.
Total time sets a hard ceiling on units
When multiple timed services are furnished in a day, the total timed minutes determine the maximum billable units, no matter how many distinct services you performed. You cannot bill 4 units for fewer than 53 minutes, period.
CMS’s own Example 4 (§20.2.C): 18 minutes of therapeutic exercise (97110) + 13 minutes of manual therapy (97140) + 10 minutes of gait training (97116) + 8 minutes of ultrasound (97035) = 49 total minutes. That’s four services, each individually over 8 minutes, but 49 minutes only supports 3 units. You bill the three services with the most time and the ultrasound goes unbilled (still documented, just not billed). Billing all four would be an overbill even though every service cleared 8 minutes.
Allocating units across codes: where most guides stop short
Once the total sets the unit count, you have to distribute those units across the codes you performed. The manual’s rules, in priority order:
- Any service performed at least 15 minutes must get at least 1 unit (at least 30 minutes → at least 2, and so on).
- Assign more units to the services that took more time.
- Compare remainders to allocate the last unit.
The remainder logic is CMS’s Example 3, and it’s the piece practices most often get wrong:
33 minutes of therapeutic exercise (97110) + 7 minutes of manual therapy (97140) = 40 total minutes → 3 units. The first 30 minutes of 97110 are two full units. Then compare the remainder of 97110 (33 − 30 = 3 minutes) against the 7 minutes of 97140, and bill the larger. Correct coding: 2 units of 97110 + 1 unit of 97140.
Note what happened: manual therapy was billed at one unit despite being performed for only 7 minutes, under the 8-minute threshold, because the day’s total supported 3 units and its remainder beat the competing remainder. Practices that “know” a sub-8-minute service can never be billed leave that unit on the table. Practices that bill 3 units of 97110 instead are assigning a unit to 3 leftover minutes, which is wrong in the other direction.
Two more official examples worth knowing cold:
- Equal times, odd unit (Example 2): 20 minutes of 97112 + 20 minutes of 97110 = 40 minutes → 3 units. Each service gets at least 1 unit; the third goes to either code (your choice), but never bill 3 of one code, because neither service individually supports 3 units.
- Several short services (Example 5): 7 + 7 + 7 minutes of three different timed services = 21 minutes → 1 unit total. Pick the one code to bill (when times are equal, any one of them); the other two services are documented but unbilled.
Documentation: what CMS actually requires
Per the Medicare Benefit Policy Manual, Ch. 15, §220.3 (Pub. 100-02), the treatment note must document total timed-code minutes and total treatment time (which includes untimed services). Time spent on each specific intervention is not required to be documented. But if you don’t capture per-service minutes somewhere, you can’t run the remainder comparison above, and neither can your biller. Capturing per-service time is how you defend the allocation, even though only the totals are mandatory.
One audit flag straight from §20.2: unit work values assume direct patient contact averaging 15 minutes per unit. A provider with “a consistent practice of billing less than 15 minutes for a unit” is explicitly called out for review. Living at the bottom of every time range is a pattern contractors can see.
Medicare’s rule vs. the AMA “Rule of Eights”
Not every payer counts the way Medicare does. Many commercial payers follow the AMA’s CPT convention, often called the Rule of Eights or substantial-portion methodology, and the difference is not cosmetic:
| Medicare 8-minute rule | AMA Rule of Eights | |
|---|---|---|
| 8-minute threshold applied to | The day’s total timed minutes | Each CPT code separately |
| Remainders from different codes | Pool toward additional units | Never combine |
| 9 min of 97110 + 9 min of 97140 | 18 total minutes → 1 unit | Each code clears 8 minutes → 2 units |
| 33 min of 97110 + 7 min of 97140 | 40 minutes → 3 units (remainder rule) | 97140 never hits 8 minutes → 2 units |
Neither method always yields more units. Per-code counting wins with several short services; Medicare’s pooling wins with mixed remainders. The operational answer is unglamorous: the counting method is a per-payer contract question. Medicare, Medicaid programs that follow Medicare methodology, and most Medicare Advantage plans use the total-time rule; commercial plans vary. Treat “which rule does this payer use?” as a required field in your payer setup, not tribal knowledge. (See APTA’s coding guidance for more on timed-code conventions.)
Related thresholds for CY 2026
Adjacent numbers that change annually (both current as of CY 2026, per CMS therapy services updates):
- KX modifier threshold: $2,480 for PT and speech-language pathology combined, and $2,480 separately for OT, up from $2,410 in CY 2025. This is not a cap on care: once a patient’s annual therapy spend crosses it, claims must carry the KX modifier attesting continued medical necessity, or they’re denied.
- Targeted medical review threshold: $3,000. Claims above it may be selected for review under CMS’s targeted process.
Quick answers to the edge cases
Can I ever bill a service performed for less than 8 minutes? Yes, when the day’s total supports the unit and that service’s minutes win the remainder comparison (CMS Example 3). Only a sole service under 8 minutes is categorically unbillable.
Do minutes from untimed codes count toward the chart? No. They’re billed as one unit each and appear only in total treatment time.
Two 7-minute timed services and nothing else? 14 total minutes → 1 unit, billed under the service performed longer (or either, if equal).
Does documentation time count? No. Pre- and post-delivery services are excluded; the clock is direct treatment only.
Do I need to write down minutes per intervention? CMS requires only total timed minutes and total treatment time, but per-service minutes are what justify your unit allocation if questioned.
Unit math is exactly the kind of thing software should get right for you. PrismEHR sums timed units per visit across codes as you document, and for Medicare patients it calculates and restricts units under the 8-minute rule automatically. Organizations can also define their own billing rules, including minute and unit restrictions, which apply at the point of documentation and are reinforced again when the claim is created. If you’re evaluating how your current system handles physical therapy billing, the 8-minute rule is a good test to run on it.