| The Medicare 8-minute rule pools the minutes of all timed services in a visit and finds the total units on a chart. The AMA Rule of Eights tests each CPT code on its own and bills one unit whenever that code passes the 8-minute midpoint. The two methods often agree but can differ by a full unit. Medicare requires its own method, while commercial payers set theirs by policy and contract. |
One 40-minute therapy visit can earn two units from one payer and three from another. That gap is a leading source of confusion in therapy billing. Our Medicare 8-minute rule guide covers the Medicare method in full. This article focuses on how the AMA method differs, how to find out which rule a payer uses, and how to run both without errors. If any term here is new, our list of medical billing terms helps.
Medicare 8-Minute Rule vs. AMA Rule: How They Work
Medicare 8-Minute Rule: The Total Time Method
CMS instructs Medicare contractors, in Pub. 100-04, Chapter 5, Section 20.2, to add all timed minutes in the visit, read the unit total from the chart, and assign units to the codes with the most time. Leftover minutes from different codes can combine to earn a unit.
AMA Rule of Eights: The Midpoint Method
CPT guidelines say a unit of time is reached once its midpoint is passed. For a 15-minute code that midpoint is 8 minutes, so each code is counted separately: 8 to 22 minutes earns one unit, 23 to 37 earns two, and so on. The method also goes by the midpoint rule and the Substantial Portion Methodology. Minutes cannot be borrowed from another code, so a service under 8 minutes earns nothing by itself.
Medicare 8-Minute Rule vs. AMA Rule: Key Differences
| Factor | Medicare 8-minute rule | AMA Rule of Eights |
| Where minutes are counted | Pooled across all timed codes | Separately for each CPT code |
| Leftover minutes | Combine across codes | Cannot combine |
| Unit ceiling | Set by total timed minutes | Sum of each code’s own units |
| A 7-minute service | Can earn a unit if the total supports it | Earns nothing |
| Typical users | Medicare Part B and programs that adopt it | Many commercial payers |
| Documentation focus | Total timed minutes and total treatment time | May require minutes per code |
Same Visit, Different Unit Counts
Neither method is always more generous. Compare these visits, where every service is a timed code:
| Visit (minutes per code) | Medicare units | AMA units |
| 97110 for 10 + 97140 for 10 | 1 | 2 |
| Three codes at 8 each (24 total) | 2 | 3 |
| Three codes at 7 each (21 total) | 1 | 0 |
| 97110 for 33 + 97140 for 7 | 3 | 2 |
| 97110 for 22 + 97140 for 22 | 3 | 2 |
| 97110 for 25 + 97140 for 20 | 3 | 3 |
The three 7-minute services show why defaults are risky: Medicare allows one unit for 21 pooled minutes, while the AMA method allows none because no code passed the midpoint. In the 33 + 7 visit, Medicare awards two units to 97110 and one to 97140, but the AMA method gives 97140 nothing. Run any visit through both calculations before assuming one is better.
Why Payers Use Different Methods
Medicare, other federal programs, and some commercial and Medicaid plans use the CMS method, while many commercial insurers follow CPT’s midpoint approach. Some publish hybrids or their own limits. In 2025, for example, APTA challenged an Anthem policy that blended both rules and required start and stop times for each code. Anthem later revised it so therapists no longer had to record those times per code. Policies change, so treat any list of which payer uses which rule as a starting point, never the final answer.
How to Confirm Which Rule a Payer Requires
Check three places in order: the contract and provider manual, the payer’s published reimbursement policy for physical medicine or timed units, and a written answer from provider relations when the policy is silent. Save the answer with its date and reference number. Settle the question during contracting and medical credentialing, before the first denials arrive. Also check daily unit limits and any authorization types that cap approved units, because those caps work separately from the counting method.
Running Both Methods in One Practice
Most clinics treat Medicare and commercial patients on the same day, so build the payer’s method into the workflow rather than relying on memory. Tag each plan in the EHR with its counting method and review date, record minutes per code as well as total timed minutes so either method can be supported, and make sure the charge on your superbills mirrors the units that payer’s rule allows. Apply one method consistently per payer. Switching methods claim by claim to raise payment is a compliance risk, not a strategy. When Medicare is secondary, confirm what each payer expects, since many practices apply the Medicare method on crossover claims.
Unit counts also decide how much of the allowed amount lands on the patient’s PR-1 deductible or coinsurance, so errors reach patient statements too. Rules-based tools described in AI billing benefits can flag a unit count that conflicts with the payer’s method, which supports practice efficiency by catching problems before submission.
Common Mistakes When Comparing the Two Rules
The most frequent errors are applying the Medicare method to every payer, assuming the AMA method always yields more units, recording only total minutes for a payer that wants minutes per code, ignoring hybrid payer policies, and relying on an outdated payer cheat sheet. Each one produces either a denial or an overpayment that may need repayment later.
Frequently Asked Questions
Is the Rule of Eights the same as the Medicare 8-minute rule?
No. The Medicare rule pools minutes across all timed codes before finding units. The AMA Rule of Eights applies the 8-minute midpoint to each code separately, so the unit counts can differ.
Which rule gives more units?
Neither always does. Ten minutes each of two codes gives Medicare one unit and the AMA method two, while 33 minutes plus 7 minutes gives Medicare three and the AMA method two.
Do commercial payers have to follow the Medicare 8-minute rule?
No. Commercial payers follow their own reimbursement policies and your contract. Many use the CPT midpoint approach, and some publish hybrid rules, so verify each payer in writing.
What is the Substantial Portion Methodology?
It is another name for the AMA midpoint approach. A unit is billed for each code once its midpoint is passed, with no pooling of minutes across codes.
How do I find out which rule a payer uses?
Read the contract and provider manual, then the payer’s timed-unit reimbursement policy. If neither answers it, request written confirmation from provider relations and keep it on file.
Key Takeaways
Medicare pools minutes, the AMA method counts each code alone, and the right choice is whichever the payer’s policy requires. Proactive Healthcare Services helps therapy practices map payer rules, configure unit logic, and keep claims clean through RCM outsourcing and practical medical billing consulting.
Simplify Therapy Billing With Expert Support
Managing different timed-unit billing rules across Medicare and commercial payers can be challenging. Proactive Healthcare Services helps healthcare practices improve billing accuracy, manage payer requirements, and streamline revenue cycle workflows with reliable medical billing and RCM support.
From payer policy verification to claim review and unit-count accuracy, our team helps your practice maintain consistent billing processes while reducing avoidable errors.
Ready to strengthen your therapy billing process?
Contact Proactive Healthcare Services to discuss your medical billing needs.
Call: +1 888-586-8881
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