Part B Therapy · Calculator
PT / OT / ST Billing Units
Convert timed treatment minutes into billable units with the Medicare 8-minute rule, then apply the PTA/OTA payment differential if an assistant delivered the care.
Data statusReference Only
- Status
- Reference Only
- Data year / effective
- CMS therapy policy
- Last reviewed
- June 2026
- Last updated
- June 2026
- Known exclusions
- 8-minute-rule mapping; untimed codes excluded
- Medical-necessity and documentation rules apply
Published reference for the stated period — confirm the current figure and any corrections at the source before billing.
Timed minutes per service
Total timed minutes
0
Billable units
0
The 8-minute rule sets total billable units from total timed minutes: 1 unit at 8–22 minutes, then one more every 15 minutes. Untimed (service-based) codes are billed one unit each and aren't counted here.
PTA / OTA differential
$100.00
When a PTA or OTA furnishes more than 10% of a service, the CQ/CO modifier applies and Medicare pays 85% of the amount. General supervision of assistants is permitted in private practice for 2026.
Unit thresholds
| Units | Total timed minutes |
|---|---|
| 1 | 8 – 22 min |
| 2 | 23 – 37 min |
| 3 | 38 – 52 min |
| 4 | 53 – 67 min |
| 5 | 68 – 82 min |
| 6 | 83 – 97 min |
Therapy modifiers
| Mod | Meaning |
|---|---|
| GP | Services delivered under a physical therapy plan of care |
| GO | Services delivered under an occupational therapy plan of care |
| GN | Services delivered under a speech-language pathology plan of care |
| KX | Threshold exceeded; services medically necessary and documented |
| CQ | Outpatient PT furnished in whole or part by a PTA — paid at 85% |
| CO | Outpatient OT furnished in whole or part by an OTA — paid at 85% |
| 59 | Distinct procedural service (also X-set: XE/XP/XS/XU) |
| GA | Waiver of liability — required ABN on file, denial expected |
| GX | Voluntary ABN issued for a non-covered service |
Reference: CMS / APTA. Verify discipline and assistant rules with your MAC.
