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Key Takeaways
- First, add up all the timed service minutes, and then use the chart to turn that number into units.
- It takes 15 minutes to treat one unit. The floor is eight minutes, not the unit itself.
- Evaluation numbers (97161 to 97168) and group therapy (97150) are not timed, so their minutes do not add up to the total timed time.
- Even though some rival books say otherwise, 97750, 97760, and 97761 are timed for 15-minute numbers.
- Mixed remainders can still get a service a unit under Medicare even if it takes less than 8 minutes if the leftover total is high enough.
- 85% of the Medicare rate is paid for PTA and OTA services that are billed with the CQ or CO modifier.
- The KX level for 2026 is $2,480 for OT and $2,480 for PT and SLP together.
What is the 8-minute rule?
Medicare uses the 8-minute rule to turn timed therapy minutes into units that can be billed. Next, use the chart to figure out how much each timed service costs: 8 to 22 minutes cost one unit, 23 to 37 minutes cost two units, 38 to 52 minutes cost three units, and so on. For every additional 15 minutes, the cost increases by one unit. Untimed codes, such as reviews, are not included in this sum at all.
It only takes one calculation to figure out how to bill Medicare for timed therapy codes. If you do it wrong, you’ll either leave units on the table or submit claims you can’t back up. The 8-minute rule applies to all timed physical therapy, occupational therapy, and speech-language pathology codes that are paid to Medicare Part B. This rule differs from how most private companies operate. This guide talks about the math, the chart, four official CMS examples, and the mistakes that get your physical therapy billing services turned down.
What Is the 8-Minute Rule?
The 8-minute rule for Medicare is based on Chapter 5, Section 20.2 of the CMS Claims Processing Manual (Publication 100-04). It applies to timed procedure codes that are billed under Medicare Part B outpatient therapy. These CPT codes track active treatment minutes while the patient is present. They are broken down into 15-minute units.
Most people think the rule works the way they expect. You don’t use it code by code. Instead, you add up all the minutes spent on timed services during a single visit and then use the chart to turn that overall number into units. Based on that total, you can bill a certain number of units, which are then split between the codes you used.
The eight minutes in the rule’s name are just the bare minimum needed to charge for one unit. That unit is still equal to 15 minutes of treatment. A lot of pricing mistakes in PT and OT businesses happen because people mix up these two numbers.
8-Minute Rule Chart (Medicare Units Table)
| Total Timed Minutes | Units Billable |
| 0 to 7 minutes | 0 (no unit billable) |
| 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 |
| 83 to 97 minutes | 6 units |
| 98 to 112 minutes | 7 units |
| 113 to 127 minutes | 8 units |
After the first row, the formula is easy to follow: start with 8 minutes for one unit and add 15 minutes for each additional unit. That’s why 23 is 8 plus 15, 38 is 8 plus 30, and so on.
Which Codes Does the 8-Minute Rule Apply To? Timed vs Untimed
This is where most mistakes begin. The 8-minute rule only takes into account timed codes. With an untimed code, you’re charged only once per session, no matter how long it lasts.
| CPT Code | Service | Timed? |
| 97110 | Therapeutic exercise | Yes |
| 97112 | Neuromuscular reeducation | Yes |
| 97116 | Gait training | Yes |
| 97140 | Manual therapy | Yes |
| 97530 | Therapeutic activities | Yes |
| 97535 | Self-care / home management | Yes |
| 97750 | Physical performance test | Yes |
| 97760 | Orthotic/prosthetic checkout | Yes |
| 97761 | Prosthetic training | Yes |
| 97032 | Electrical stimulation (manual) | Yes |
| 97035 | Ultrasound | Yes |
| 97161-97168 | PT and OT evaluations | No (untimed) |
| 97150 | Therapeutic exercises, group | No (untimed) |
| 97012 | Traction, mechanical | No (untimed) |
| G0283 | Electrical stimulation (unattended) | No (untimed) |
| 92507 | Treatment for speech, language (SLP) | No (untimed) |
One important change: 97750, 97760, and 97761 are timed 15-minute codes per CPT. Some written guides say they are not timed. When those codes appear in a session, that error increases the number of units counted.
Under 97150, group treatment is paid only once per patient, no matter how long the session lasts. Its minutes don’t affect how timed units are calculated.
What Counts as Timed Treatment Minutes?
The CMS manual has a direct answer to this question. This matters because room time and total treatment time are not the same.
The minutes you time are the ones you actually spend treating the patient while they are there. That includes time spent doing things with the patient, leading therapeutic exercises, and tasks where your skill is what the service is for. In addition, the time spent on assessment and management that is necessary to carry out the intervention is included, such as taking the patient’s vital signs before starting physical treatment or looking at how they are responding before going on to the next step, as long as this time is written down in the note.
Time spent before the patient arrives, time spent documenting after the patient leaves, time spent with other patients, and time the patient exercises on their own without your help don’t count. A Medicare audit will catch you when you still use the old method of counting “time in the clinic” for timed codes. The number in the note has to match what happened in the hospital.
The CPT manual adds one important detail that you should know. For timing codes, CPT lets you use assessment and control time as part of the therapy process. So, if you look at the joint for two minutes before manual therapy to figure out how to do it, that two minutes can be counted toward the 97140 time as long as it’s part of the service and not a separate evaluation. Write down the clinical reason in the note.
How to Calculate PT Billing Units Step by Step
Five steps. No shortcuts.
Step 1: Record the minutes spent on each timed code. Write this down in the clinical note, with a separate line for each procedure.
Step 2: Total the timed minutes. Add all timed codes together. Do not include evaluation codes, group therapy, or unattended modalities.
Step 3: Use the chart. In the left column, you’ll see your total. That’s the most units you can charge for the whole event.
Step 4: Assign full 15-minute units first. Each code that lasted 15 minutes gets one unit to begin. Assign full units until you’ve used up all the codes that take the most time.
Step 5: Allocate remaining units by leftover minutes. When the full units aren’t enough, look at the minutes left over per code. The next unit goes to the code that has the most minutes left.
Mixed Remainders: Which Code Gets the Last Unit?
Most billing teams get this rule wrong. Medicare says that a code that was handled for less than 8 minutes can still get a unit through mixed remainders, as long as the total number of minutes left over from all the codes in the session is at least 8.
Let’s say you worked on 97110 for 20 minutes and 97140 for 7 minutes. Total number of minutes: 27. That’s two units. The chart backs it up. One full unit is given to 97110, which covers 15 of its 20 minutes. The remaining 5 minutes from 97110 and 7 minutes from 97140 total 12, enough for a second unit. The second unit goes to 97140 since it still has the most pool time left.
The tie rule says that either code can get the unit if two codes have exactly the same number of minutes left. That being said, no code can ever get more units than its own minutes can handle.
CMS Examples: 8-Minute Rule in Action
These four examples come directly from CMS, via the First Coast Service Options manual summarizing Publication 100-04, Chapter 5, Section 20.2.
| Session | Minutes Per Code | Total | Units | Allocation |
| Example 1 | 97112: 24, 97110: 23 | 47 min | 3 units | 2 x 97112, 1 x 97110 |
| Example 2 | 97112: 20, 97110: 20 | 40 min | 3 units | 2 of one, 1 of the other (not 3 of either) |
| Example 3 | 97110: 33, 97140: 7 | 40 min | 3 units | 2 x 97110, 1 x 97140 (mixed remainder applies) |
| Example 4 | 97110: 18, 97140: 13, 97116: 10, 97035: 8 | 49 min | 3 units | 1 each of 97110, 97140, 97116; 97035 gets no unit but must be documented |
It’s important to look at Example 4 because it shows what happens when you split time into four codes. Ninety-three minutes, three units, and 97035 are recorded but not paid. Write down everything that took place. Only charge what the math says you should.
8-Minute Rule vs Rule of 8s: What’s the Difference?
These two methods are often confused. They produce different unit counts for the same session.
| Calculation Method | How It Works | Who Uses It |
| CMS 8-Minute Rule | Totals all timed minutes, converts to units across the whole session | Medicare Part B |
| CPT Rule of 8s (AMA) | Counts each code separately; a unit is billable once you pass the midpoint (more than 7.5 minutes of a 15-minute unit) | Commercial payers: varies by contract |
See how it appears in real life here. Say a patient receives 97110 for 8 minutes and 97140 for 8 minutes, for a total of 16 timed minutes.
1 unit = 16 minutes of timed labor under CMS. Only one code is needed.
Each code was billed as 1 unit, for a total of 2 units, since each stood alone for 7.5 minutes under the CPT Rule of 8s.
This makes a difference. Medicare has its way. A payer contract might supersede both; therefore, review the payer policy before assuming Medicare’s way applies. If the client’s contracts have differing criteria, the APTA’s code rules allow for this circumstance.
Which Payers Use the 8-Minute Rule?
This is one of the most common sources of billing errors in multi-payer practices. Medicare Part B uses the CMS method. Many other payers do not.
| Payer | Method | Notes |
| Medicare Part B | CMS 8-minute rule | Total timed minutes converted per session; CMS §20.2 governs |
| Medicare Advantage | Varies by plan | Most plans follow Medicare Part B rules but check the plan’s provider manual; not guaranteed |
| Medicaid | Varies by state | Some states mirror Medicare; others use the CPT Rule of 8s or a state-specific approach; check the state’s provider manual directly |
| TRICARE | Generally follows Medicare method | Verify with the TRICARE provider handbook for therapy services |
| Commercial (Blue Cross, Aetna, UHC, etc.) | Typically CPT Rule of 8s | Per-code midpoint rule is common; your contract terms control, not the payer’s standard policy |
| Workers’ Compensation | Varies by state and carrier | Some states use Medicare’s method; many use a fee schedule with time-based units defined differently |
Usually, when a contract specifies the buyer is following CPT code guidelines, it’s the Rule of 8s technique, not the CMS way. In the same session, these two approaches can give you different unit counts. Which means you earn a different amount of money from the same consumer.
APTA’s coding rules include how to handle payers that don’t follow either approach. If the contract includes anything outside of CPT or CMS, the contract wording controls.
PTA and OTA Services: CQ/CO Modifiers and the 10% Rule
A CQ modifier (PTA) or CO modifier (OTA) must be added to the claim for services provided by a physical therapist assistant or an occupational therapy assistant. When the modifier is present, Medicare pays 85% of the standard rate for these.
In the 10% de minimis exception, the full rate is applied if the helper worked 10% or less of the total scheduled minutes in a session. The adjustment is not needed in this case.
Two specific exceptions apply for 2022. The last timed unit can be billed without the CQ or CO decrease if the supervising therapist gives at least 8 minutes of it in a session. And if both the therapist and the helper work for 9 to 14 minutes, for a total of 23 to 28 minutes, the full rate can be charged for the last two units in that range as long as certain conditions are met for recording. Write down who gave each minute. This lack of clarity creates an audit risk.
2026 Medicare Therapy Updates That Affect Your Claims
In 2026, some numbers and rules changed. Before your next billing cycle, you should know about these changes.
The KX modifier threshold is $2,480 for PT and SLP services combined and $2,480 for OT services alone. After spending this much on therapy through Medicare in a year, the KX tag must be added to all future timed therapy claims to prove that the patient’s treatment is medically necessary. Claims over that amount will not be paid without it.
The target amount for a medical review is $3,000 per bucket. Medicare Administrative Contractors look more closely at claims above this amount.
For telehealth services, the Consolidated Appropriations Act of 2026 allows physical therapists, occupational therapists, and speech-language pathologists to bill Medicare until December 31, 2027. The 8-minute rule applies to in-person visits and telehealth sessions.
Each timing code must show up on its own claim line by date of service. This rule has been in place since April 19, 2021. Claims that put together timed codes on one line are turned down.
Does the 8-Minute Rule Apply Outside Therapy?
No. It’s not the CMS 8-minute rule that’s used to bill for psychotherapy, evaluation and management services, and most other timing codes. Instead, they use different time-based billing methods.
Most people get confused about psychotherapy codes, which are also based on time. CPT psychotherapy codes have set time ranges. For example, 90832 covers 16 to 37 minutes, 90834 covers 38 to 52 minutes, and 90837 covers 53 minutes or more. No unit conversion is used for billing; instead, a code is chosen based on total session time. “8 to 22 minutes = 1 unit” doesn’t make sense. Bill a psychotherapy session with the code that matches its length, once per session.
Since January 2021, evaluation and management numbers (99202 to 99215) have been used for medical decision-making throughout. Total time for E/M reasons includes work done before and after the service, but not during the service itself. This work is specifically left out of the figures for timed treatment minutes. You shouldn’t mix these two systems together because they are different.
CMS’s outpatient therapy rule is the 8-minute rule. It stays in Chapter 5 of the Claims Processing Manual, which is about therapy services.
Documentation That Supports Your Units
Medicare checks treatment claims by matching what the therapist charged with what the clinical note says. The claim fails review if the note lists only 25 minutes of therapeutic exercise, but the claim shows 3 units, which means at least 38 timed minutes of exercise total. Units have to go back to minutes that were written down.
The following should all be on a note that supports timed unit billing:
Minutes per timed procedure. “30 minutes of treatment” should read “97110 Therapeutic Exercise: 20 minutes; 97140 Manual Therapy: 15 minutes.” The note needs to break down the total, not just list the total.
Total timed treatment minutes and total treatment time. Some MACs check the ratio of these two numbers. Write down both.
Who provided the service
The note must state what the PTA or OTA did and for how long, if they participated. This backs up the choice to use the CQ/CO modifier.
Skilled treatment rationale
The note must document not only what was done, but also why the services required a licensed therapist. Changes in function, patient response, and clinical decision-making all support the need for skilled care.
A sample note template that works:
PT for 35 minutes with skilled intervention. 97112 Neuromuscular reeducations: 20 minutes (checked for activity of both hip flexors and led the patient through three sets of lateral band walks while giving them comments on their pelvic position). 97140 Manual therapy: 15 minutes of Grade III tibiotalar joint mobilization, which the patient could handle and said made them less stiff. Total number of minutes: 35. Two units were billed (97112 times 1, 97140 times 1). No help from the PTA.
That note lists 35 timed minutes (2-unit range per chart), assigns units to named codes, keeps track of both treatment time and timed treatment time separately, and makes sure the right person provided the service. It holds up in court.
Common 8-Minute Rule Mistakes
| Mistake | Why It’s Wrong | Fix |
| Applying the rule per code instead of per session | Medicare totals all timed minutes first | Total the session minutes, then convert |
| Including eval minutes in the timed total | Evals are untimed | Keep eval codes out of the timed count |
| Listing 97150 group therapy in units | Group is billed once per patient | Charge 1 unit of 97150 per session |
| Choosing the higher-paying code for the extra unit | Allocation follows time, not fee schedule | The code with the most leftover minutes gets the unit |
| Billing units the note doesn’t document | Medicare audits the minutes in the note | Match billed units to documented timed minutes |
Frequently Asked Questions
What is the 8-minute rule in physical therapy?
CMS uses the 8-minute rule to figure out how much to charge for timed therapy codes. Add up all the minutes for all the timed services in one visit. For every 15 minutes over 37, you’ll be charged an extra unit. From 8 to 22 minutes, you’ll be charged one unit. The rule is for outpatient PT, OT, and SLP timing codes under Medicare Part B.
How many units are 30 minutes of therapy?
Because 30 minutes of timed treatment is between 23 and 37 minutes, it is billed as 2 units under the 8-minute rule.
How many units are 45 or 60 minutes?
It costs 3 units for 45 minutes (38 to 52 range). It costs 4 units for sixty minutes (53 to 67 range).
Does the 8-minute rule apply to evaluations?
No. Evaluation codes 97161 to 97168 are not timed and are only charged once per session. Their minutes are not used to figure out the timed unit.
What is the difference between the 8-minute rule and the Rule of 8s?
The CMS 8-minute rule adds up all the minutes that were timed during a session and then turns that number into units. If a code exceeds the 7.5-minute mark, it earns a unit under the CPT Rule of 8s, which many commercial payers use. Each method can give different unit counts for the same session.
Does every insurance company use the 8-minute rule?
No. CMS uses the 8-minute rule for Medicare Part B. Different groups have different rules for Medicare Advantage plans, Medicaid, TRICARE, private insurance, and workers’ compensation programs. Before assuming the Medicare method will work, check the payer’s rules and your contract.
Does Medicaid use the 8-minute rule?
It’s different in each state. Some state Medicaid programs use the same method as Medicare, while others use the CPT Rule of 8s or a method that is unique to their state. Look at the state’s Medicaid provider handbook right away.
Can you bill a code performed for less than 8 minutes?
Under Medicare, yes, through a mix of payments. If all the timed codes in the session have at least 8 minutes left over, the code with the most minutes can still get a unit, even if its own minutes were less than 8.
Does the 8-minute rule apply to PTAs and OTAs?
Yes, for tracking units. The same calculation for timed units is used. Services provided by a PTA or OTA are billed with the CQ or CO modifier and paid at 85% of the Medicare rate, with a few exceptions for the de minimis rule and certain minutes provided by a supervisor.
Does the 8-minute rule apply to telehealth therapy?
Yes. The units are calculated the same way for both in-person and telehealth visits. Medicare allows PTs, OTs, and SLPs to use telemedicine until December 31, 2027.
Free 8-Minute Rule Cheat Sheet
Everything on this page is summed up on the one-page cheat sheet below, which you can keep at your billing station. It talks about the units chart, the five-step allocation process, the difference between Rule of 8s and CMS, and the basics of the CQ/CO modifier for PTA/OTA sessions.
Download the cheat sheet here: 8-Minute Rule Cheat Sheet 2026 (PDF)
The PDF file is named 8-minute-rule-cheat-sheet.pdf. It’s updated every January when CMS releases the new KX thresholds. Staff at the front desk or in the hospital will use the chart on the first page the most if you give it to them.
Final Thoughts
Once you understand the basic logic behind the 8-minute rule, it’s not hard to get it right: first add up the timed minutes, then convert to units second, and finally assign. People get denied claims when they skip the first step, add timed and untimed codes incorrectly, or use the wrong method for a payer that isn’t Medicare.
If your practice regularly submits Medicare treatment claims and you’re seeing unit-related rejections or recoupments, it’s not a lack of understanding; it’s paperwork and process issues. When you compare your PT claims to the minutes you recorded, a medical billing audit will often find trends that help you get more money back than the audit costs.
If a practice wants to take some of the billing work off of the clinical team, our physical therapy billing services cover the whole process, from figuring out the units to handling denials. They are based on the specific documentation requirements Medicare has for timed codes.
