The Question · Physical therapy · Timed codes
One visit, two unit counts. Your contract decides which one is right.
Medicare adds up all timed minutes, then converts. The CPT midpoint rule, applied code by code, counts each service on its own. Run the five CMS examples both ways and the unit count moves up or down. Here is how to know which rule each payer expects.
By ASP-RCM Editorial, Healthcare RCM Practice · Updated
The question we asked on LinkedIn
Medicare's own example: 24 min of 97112 plus 23 min of 97110 bills 3 units. Counted code by code, it is 4. Do you bill every payer the Medicare way, or read each contract?
Minimum for one timed unit
Medicare does not bill a lone timed service under 8 minutes, per the Claims Processing Manual, ch. 5, sec. 20.2
Units for the same 47 minutes
CMS Example 1 bills 3 units on total time. The same minutes counted per code reach 4.
Three services, 7 minutes each
CMS Example 5 bills one unit on 21 total minutes. Per code, no service reaches 8 minutes.
Commercial policy that follows Medicare
Anthem commercial reimbursement policy (NY), effective August 13, 2025, uses the total-minutes table
Two ways to turn minutes into units
Both start at 8 minutes for the first 15-minute unit. They differ on whether leftover minutes from different codes can be pooled.
Per code: CPT midpoint rule applied to each code
- CPT: a unit of time is attained when the midpoint is passed
- Each code stands alone: 8 minutes for unit 1, 23 minutes for unit 2
- Leftover minutes from different codes are not pooled
- Often called the substantial portion methodology or the rule of eights
Total time: the Medicare 8-minute rule
- Add all timed minutes for the day, then read the CMS table (8 to 22 minutes = 1 unit, 23 to 37 = 2)
- Total minutes cap the total units billed
- Remainders under 8 minutes can combine into one unit
- Extra units go to the service with the most minutes
The five CMS examples, counted both ways
Minutes are from Medicare Claims Processing Manual, chapter 5, section 20.2. The per-code column applies the CPT midpoint rule to each code separately.
| CMS example | Minutes by code | Medicare total-time units | Per-code units |
|---|---|---|---|
| 1 | 97112: 24, 97110: 23 (47 total) | 3 | 4 |
| 2 | 97112: 20, 97110: 20 (40 total) | 3 | 2 |
| 3 | 97110: 33, 97140: 7 (40 total) | 3 | 2 |
| 4 | 97110: 18, 97140: 13, 97116: 10, 97035: 8 (49 total) | 3 | 4 |
| 5 | 97112: 7, 97110: 7, 97140: 7 (21 total) | 1 | 0 |
Per-code counts are our arithmetic on the CMS minutes. Which method applies depends on the payer's policy and your contract, not on the clinic's preference.
Neither method always pays more
Per-code counting wins when two services each run past 23 minutes. Total time wins when short services add up.
Source: CMS Medicare Claims Processing Manual, ch. 5, sec. 20.2, Examples 1 and 3. Billing more units than the payer's method allows is an overpayment, not upside.
How to set the unit rule for each payer
Read the contract
Look for a timed-code or units clause, or a reference to the payer's reimbursement policy manual.
Pull the payer policy
Find the reimbursement policy for therapy or timed codes. Note its number and effective date.
Map it in the billing system
Set the unit rule per payer, not one rule for the clinic. Keep Medicare on the CMS total-time table.
Document minutes per code
Medicare requires total timed minutes. Per-code payers need minutes for each code to support each unit.
Recheck yearly
Policies are revised. Re-pull each policy at renewal and when denials on timed codes rise.
Three things that trip clinics up
Commercial does not mean per code
Anthem's commercial policy C-07002 (NY) uses the Medicare total-minutes table. Assume nothing; read each policy.
One rule in the EMR
A system hard-coded to the 8-minute rule will over-bill some per-code payers and under-bill others on the same day.
Untimed codes are outside both
Evaluations and other untimed codes bill one unit regardless of minutes. Neither method applies to them.
Check your unit setup in five minutes
Tick what is true for your clinic today.
Medicare counts total minutes. Other payers may count each code on its own. Tie every payer to its written unit rule, document minutes per code, and let the billing system apply the right rule per claim.
Questions operators ask next
What is the difference between the 8-minute rule and the substantial portion method?
The Medicare 8-minute rule adds all timed minutes in a day and converts the total to units using the CMS table. The substantial portion method, also called the rule of eights, applies the CPT midpoint rule to each code separately, so leftover minutes from different codes are not pooled. The same visit can produce more or fewer units.
Do all commercial payers use the substantial portion method?
No. Payers set their own rule. For example, Anthem's commercial reimbursement policy C-07002 for New York, effective August 13, 2025, uses the same total-minutes table as Medicare. Read each payer's reimbursement policy and your contract before setting units, and keep the policy number on file.
How many minutes do I need to bill two units under the 8-minute rule?
Under the Medicare table, 23 to 37 total timed minutes bills 2 units, 8 to 22 minutes bills 1 unit, and 38 to 52 minutes bills 3 units. When several timed services are given, total minutes cap total units, and extra units go to the service with the most minutes.
What should a PT note document for timed codes?
Medicare requires the total timed minutes and the total treatment minutes, and says time for each intervention is not required in the note. Payers that count per code need minutes for each code to support each unit, so recording minutes per code covers both methods.
Not sure which unit rule each of your payers expects?
Send us 90 days of PT denials and remits. A senior therapy billing partner maps each payer to its unit rule, shows where units were lost or put at risk, and sends a written gap report after a free 30-minute call.
Keep reading
Sources
- CMS, Medicare Claims Processing Manual, Chapter 5, Section 20.2 (Rev. 3670)
- Anthem Blue Cross, Commercial Reimbursement Policy C-07002 (NY), effective August 13, 2025
- North Dakota Health and Human Services, Medicaid Claims Guidance (time-based units)
- The ASHA Leader, The Right Time for Billing Codes, March 2018 (CPT midpoint rule)
Checked November 4, 2026. Per-code unit counts are our arithmetic on the CMS examples. Payer policies change; confirm the current policy and your contract before billing. General information, not legal advice.