The Medicare 8-Minute Rule: How Therapy Units Are Counted
The Medicare "8-minute rule" sets how many billable units a physical, occupational, or speech therapist can charge for time-based (timed) therapy services under Medicare Part B. A provider must furnish at least 8 minutes of a timed service to bill a single 15-minute unit of it. Each unit represents 15 minutes of direct, one-on-one patient contact, and 8 minutes is just past the halfway mark. When several timed services are given on the same day, Medicare adds up the total minutes of all timed services and uses an official chart to decide the total number of units you can bill — this is the CMS "total-time" method, which is defined in the Medicare Claims Processing Manual, Chapter 5, Section 20.2.
What the 8-minute rule is
Many outpatient therapy services are billed in 15-minute units, where one unit is meant to equal 15 minutes of direct, hands-on (one-on-one) time with the patient. The problem is that real sessions rarely divide neatly into 15-minute blocks. The 8-minute rule is Medicare's method for rounding the actual minutes spent into a whole number of billable units.
The core idea is simple: a service must be performed for at least 8 minutes before any single unit of it can be billed, because 8 minutes is just past the halfway point of a 15-minute unit. No timed unit may be billed for a service performed for fewer than 8 minutes. The rule's official name in the Medicare manuals is "Counting Minutes for Timed Codes in 15 Minute Units."
This rule applies to outpatient therapy billed under Medicare Part B using time-based therapy codes. It does not change what care you receive — it governs how the therapist's time is translated into units on the claim.
The official units-to-minutes chart
CMS publishes a fixed table that tells providers how many minutes of timed service equal how many billable units. The first unit covers a wide range (8 through 22 minutes), and every additional 15 minutes adds one more unit. The threshold to reach the next unit always lands 8 minutes into that next 15-minute block.
- 1 unit = 8 through 22 minutes
- 2 units = 23 through 37 minutes
- 3 units = 38 through 52 minutes
- 4 units = 53 through 67 minutes
- 5 units = 68 through 82 minutes
- 6 units = 83 through 97 minutes
- 7 units = 98 through 112 minutes
- 8 units = 113 through 127 minutes
Timed codes vs. untimed codes
The 8-minute rule only applies to timed (time-based) codes. These are services that are billed in 15-minute increments because the value of the service depends on how long it is performed.
Untimed (service-based) codes work differently. They are entered as "1" in the units field no matter how many minutes were spent. For example, an evaluation code such as 92521 is untimed and is billed as one unit regardless of how long the evaluation took. You do not run untimed codes through the 8-minute chart.
- Common timed codes subject to the rule: 97110 (therapeutic exercise), 97112 (neuromuscular reeducation), 97116 (gait training), 97140 (manual therapy), 97530 (therapeutic activities), 97035 (ultrasound)
- Timed codes: minutes are run through the 15-minute-unit calculation
- Untimed codes: always billed as 1 unit each, regardless of duration
Billing when several timed codes are used in one visit (the total-time method)
When more than one timed service is provided on the same day, Medicare does not check each code separately. Instead, it adds up the total minutes of all timed services and uses the chart above to find the total number of billable units. The total number of units is capped by the total treatment minutes. After you know the total units allowed, you assign more units to the service that took the most time.
CMS Example 1: 24 minutes of 97112 plus 23 minutes of 97110 = 47 total timed minutes. The chart says 47 minutes = 3 units. Correct coding is 2 units of 97112 and 1 unit of 97110, because 97112 took the most time.
CMS Example 4 shows the cap in action: 18 minutes of 97110 + 13 minutes of 97140 + 10 minutes of 97116 + 8 minutes of 97035 = 49 total minutes. Even though four separate services were performed, only 3 units are allowed because you cannot bill 4 units for fewer than 53 minutes. The ultrasound (97035) cannot be billed as its own unit — but it should still be documented in the record.
This is why you cannot bill an extra unit just because you provided more services than the total time supports. The total minutes always control the maximum number of units.
Leftover (remaining) minutes
Sometimes several services are each performed for fewer than 8 minutes, so none of them individually qualifies for a unit. Medicare lets you combine these leftover minutes. If two timed services are each performed for 7 minutes or fewer but together total 8 or more minutes, you bill one unit for the service performed for the most minutes. The same logic applies when three or more short services are combined.
CMS Example 5: three services at 7 minutes each — 97112, 97110, and 97140 — total 21 minutes. The chart says 21 minutes = 1 unit, so you select one CPT code to bill for that single unit.
If two codes were performed for the exact same amount of time and you can only bill one of them, you choose one to report — there is no requirement to split a single unit.
Documentation requirements
The chart is only for rounding into 15-minute units. It does not mean minutes before the 8th are excluded — all direct treatment minutes count toward the total. Therapists must document the total active treatment minutes for all timed codes, as well as the total treatment minutes (including time spent on untimed codes).
Per the Medicare Benefit Policy Manual, Chapter 15, Section 220.3B, the time spent on each specific intervention does not have to appear in the treatment note, but the total number of timed minutes must be documented in the record. Even a service that cannot be billed (like the ultrasound in Example 4) should still be documented as care that was provided.
CMS total-time vs. the AMA 'Rule of Eights'
There are two different ways to apply an 8-minute threshold, and they can produce different results. Medicare (CMS) uses the total-time method described above: add all timed minutes together, then look up the total units. The AMA CPT approach, sometimes called the "Rule of Eights" or "Rule of 8s," instead requires each timed code to independently reach 8 minutes before any unit of it can be billed.
Because Medicare uses the total-time method in Section 20.2, leftover minutes from different short services can be combined to support a unit — something the AMA per-code rule would not allow. Knowing which payer's method applies matters, because it changes how many units can be billed.
Where it applies and what you pay
The 8-minute rule applies to outpatient therapy — physical therapy (PT), occupational therapy (OT), and speech-language pathology (SLP) — billed under Medicare Part B time-based CPT codes. It is a Medicare billing rule. Medicare Advantage plans and private insurers may follow Medicare's total-time method or may use the AMA "Rule of Eights" instead; the exact unit-counting method can vary by plan, so confirm your plan's billing rules and check your Evidence of Coverage.
For covered Part B outpatient therapy, after you meet the annual Part B deductible you generally pay 20% coinsurance of the Medicare-approved amount for the services (units) billed. Because the number of units affects the approved amount, the units determined by the 8-minute rule directly affect your share of the bill.
- 2026 Part B annual deductible: $283
- Part B coinsurance after the deductible: 20% of the Medicare-approved amount
- 2026 standard Part B monthly premium: $202.90 (paid by all Part B enrollees)
Frequently asked questions
How many minutes do I need to bill one unit of a timed therapy code?
At least 8 minutes. A single timed service performed for fewer than 8 minutes cannot be billed as a unit. Per the CMS chart, 8 through 22 minutes equals 1 unit, and each additional 15 minutes adds another unit (23-37 = 2 units, 38-52 = 3 units, and so on).
Why can't I bill 4 units when I performed 4 different services?
Because the total number of units is capped by the total treatment minutes, not by how many services you performed. The chart requires at least 53 total minutes to reach 4 units. In CMS Example 4, four services totaled only 49 minutes, so just 3 units could be billed — the lowest-time service couldn't be billed separately, though it still had to be documented.
What is the difference between the CMS 8-minute rule and the AMA 'Rule of Eights'?
Medicare's 8-minute rule uses the total-time method: it adds up all timed minutes for the day, then looks up the total units. The AMA 'Rule of Eights' instead requires each timed code to independently reach 8 minutes. Under Medicare's method, leftover minutes from short services can be combined to support a unit; under the AMA method they cannot.
Does the 8-minute rule apply to physical, occupational, and speech therapy?
Yes. It applies to outpatient PT, OT, and SLP services billed under Medicare Part B using time-based CPT codes such as 97110, 97112, 97116, 97140, 97530, and 97035.
What documentation does Medicare require for timed therapy minutes?
The total number of timed minutes must be documented in the record, along with the total treatment minutes (including untimed-code time). Per the Medicare Benefit Policy Manual, Chapter 15, Section 220.3B, the time for each individual intervention does not have to be listed, but the totals do.
What will I pay out of pocket for Medicare-covered outpatient therapy?
After you meet the 2026 Part B annual deductible of $283, you generally pay 20% coinsurance of the Medicare-approved amount for the units billed. The number of units determined by the 8-minute rule affects the approved amount and therefore your share.
Sources
Related guides
Medicare Login Guide is an independent resource and is not affiliated with or endorsed by Medicare, the Centers for Medicare & Medicaid Services, or any government agency. This article is for general information only — confirm current figures and your specific options at medicare.gov or by calling 1-800-MEDICARE.