The 8-minute rule in physical therapy, with worked examples

What the 8-minute rule is in physical therapy

Many physical therapy codes are timed codes, billed in 15-minute units. Patients rarely get services in neat 15-minute blocks, so payers need a rule for partial units. The 8-minute rule is Medicare’s rule: a unit can be billed once at least 8 minutes of timed service have been provided, because 8 minutes is more than half of 15.

The detail that trips people up is what those 8 minutes are counted against. Under Medicare, you add up the minutes of all timed services in the session first, then convert the total into units. The same method applies to occupational therapy and speech-language pathology timed codes billed to Medicare.

How Medicare counts total timed minutes into units

Add the minutes of every timed code provided that day, then use this scale:

• Under 8 minutes: 0 units
• 8 to 22 minutes: 1 unit
• 23 to 37 minutes: 2 units
• 38 to 52 minutes: 3 units
• 53 to 67 minutes: 4 units
• 68 to 82 minutes: 5 units

The pattern continues in 15-minute steps. Once you know the total units, you assign them to the individual codes. Each code gets a unit for every full 15 minutes it was performed. Any units left over go to the services with the most remaining minutes.

Worked examples of the 8-minute rule

Example 1: two codes, one under 8 minutes

33 minutes of therapeutic exercise (97110) and 7 minutes of manual therapy (97140). Total timed minutes: 40, which is 3 units.

Therapeutic exercise has two full 15-minute units (30 minutes) with 3 minutes left over. Manual therapy has 7 minutes. The third unit goes to the service with more remaining minutes, which is manual therapy. Bill 2 units of 97110 and 1 unit of 97140.

Notice that manual therapy gets a unit with only 7 minutes. That’s correct under Medicare’s method, because Medicare applies the 8-minute threshold to the session total.

Example 2: two codes with similar time

24 minutes of neuromuscular reeducation (97112) and 23 minutes of therapeutic exercise (97110). Total: 47 minutes, which is 3 units.

Each code has one full unit, with 9 and 8 minutes remaining. The third unit goes to neuromuscular reeducation, which has more remaining time. Bill 2 units of 97112 and 1 unit of 97110.

Example 3: three short services

7 minutes each of therapeutic exercise, manual therapy and therapeutic activities (97530). Total: 21 minutes, which is 1 unit.

All three are tied, so only one can be billed. Medicare’s guidance is to bill the service that took the most time, and when times are equal, to choose the one that’s most clinically appropriate.

Example 4: untimed code plus a little timed work

A physical therapy evaluation plus 5 minutes of therapeutic exercise. The evaluation is billed as 1 unit regardless of time. The timed total is 5 minutes, so no timed units are billed.

Timed codes vs untimed (service-based) codes

Only timed codes count toward the total. Untimed codes are billed once per session no matter how long they took, and their minutes stay out of the 8-minute calculation.

• Common timed codes include therapeutic exercise (97110), neuromuscular reeducation (97112), gait training (97116), manual therapy (97140), therapeutic activities (97530), self-care training (97535), and constant-attendance modalities such as ultrasound (97035) and manual electrical stimulation (97032).
• Common untimed codes include the physical therapy evaluations and re-evaluation (97161 to 97164), supervised modalities such as unattended electrical stimulation and mechanical traction, and group therapy (97150).

A frequent error is adding evaluation time or hot pack time into the timed total, which inflates the units. Payers check this, and an audit that finds a pattern of it can lead to recoupment across many claims.

The substantial portion method some commercial payers use

Medicare’s total-minutes method isn’t universal. Some commercial payers follow the CPT “substantial portion” approach, sometimes called the per-code method. Under it, each timed code is counted separately, and a code needs at least 8 minutes of its own to be billed.

Run the examples above that way and the results change:

• Example 1: 33 minutes of 97110 is 2 units, and 7 minutes of 97140 is 0. That’s 2 units instead of 3.
• Example 3: no code reaches 8 minutes, so nothing timed is billable.

Some Medicaid programs and Medicare Advantage plans follow Medicare’s method and others set their own rules, so check each payer’s policy and build it into your billing rules by payer. Applying Medicare’s method to a per-code payer overbills. Applying the per-code method to Medicare underbills.

Documentation that supports your units

Medicare requires the treatment note to record the total timed code treatment minutes and the total treatment time, including untimed services, along with the interventions provided. Start and stop times aren’t required.

In practice, recording minutes for each timed code is the safer habit. It shows how the units were assigned, it’s what per-code payers need, and it makes an audit much easier to answer. The note should also show that the services were skilled and tied to the plan of care. Minutes alone don’t prove medical necessity.

Two other habits help. Count only direct treatment time, and leave out time the patient spends waiting. And make sure the billed units match the minutes in the note before the claim goes out.

GP, GO and KX modifiers on therapy claims

• GP, GO and GN identify services delivered under a physical therapy, occupational therapy or speech-language pathology plan of care. Medicare requires them on outpatient therapy claims, and a missing or wrong discipline modifier is an easy denial.
• KX applies once a patient’s therapy charges for the year pass Medicare’s annual threshold amount. It attests that the services are medically necessary and that the record supports it. Physical therapy and speech-language pathology share one threshold, and occupational therapy has its own. CMS updates the amount each year, and claims above a higher level can be selected for targeted medical review.
• CQ and CO identify services furnished in whole or in part by a physical therapist assistant or occupational therapy assistant. Medicare pays these at a reduced rate, and the rules on when they apply are specific, so check current CMS guidance.

Our physical therapy billing page covers how we handle units, modifiers, authorizations and visit limits for therapy practices. Commercial plans often add visit limits and authorization requirements, which we cover in prior authorization in medical billing.

If you’d like to know whether your units are being billed correctly by payer, ask for a free A/R audit. We’ll review your recent claims and you keep the findings either way.