Calculating Time
Pexels: Tima Miroschnichenko
Calculating total time can be confusing, but once you master a few concepts it gets much easier. The key is making sure you are applying the right construct to the appropriate set of time-based codes.
The Midpoint Rule (CPT pg. xix)
When a CPT code descriptor includes time (e.g., “30 minutes”), a unit of time is attained once the midpoint is passed. In practical terms, an hour is “reached” at 31 minutes; a 30‑minute service is “reached” at 16 minutes.
Example:
- 90832 (30 min): 16–37 minutes
- 90834 (45 min): 38–52 minutes
- 90837 (60 min): 53+ minutes
- Select the code that most closely matches the actual time spent.
The 8-minute Therapy Rule (CMS)
The Medicare 8‑minute rule applies to outpatient PT, OT, and SLP (15‑minute) timed codes under Part B. To determine the total therapy units, all minutes are totaled to determine how many units can be billed.
Common PT 15‑minute timed CPT codes
- 97110 – Therapeutic Exercise
- 97112 – Neuromuscular Re‑education
- 97116 – Gait Training
- 97140 – Manual Therapy
- 97530 – Therapeutic Activities
These codes are billed in 15‑minute units and use Medicare’s 8‑minute thresholds:
- 8–22 min = 1 unit
- 23–37 min = 2 units
- 38–52 min = 3 units
Remember, the 8-minute therapy rule is different from the CPT midpoint rule.
Example:
A physical therapist provides:
- 18 min of therapeutic exercise (97110)
- 10 min of manual therapy (97140)
Total timed minutes = 28
→ Falls in 23–37 min = 2 units.
Assign units based on which code took more time: - 97110 = 1 unit
- 97140 = 1 unit
Exact Time (CPT/CMS)
The midpoint rule does not apply to E/M codes that use total time on the date of the encounter—these codes require you to meet the full published time threshold before you can bill by time.
There is one major exception under CPT: critical care. CPT allows you to bill +99292 (in addition to 99291) once you reach 75 minutes of total critical care because CPT uses a midpoint approach. Medicare (CMS) does not follow this. CMS requires the full additional 30 minutes—meaning you must reach 104 minutes of total critical care time before +99292 can be reported.
Example:
Critical care physician spent a total time of 90″ (all criteria met, of course).
CMS: 99291 only (didn’t reach full 104″ requirement) CPT: 99291, 99292 (past midpoint)
Of course, there are other constructs to consider when using time to report a service. You also need to consider who you are working with and whether or not there are additional rules and concepts that need to be layered on. You may split/share time under the right advance practitioner circumstances. Contrastingly, you may never count student or resident/fellow time apart from the attending under teaching physician guidelines. For critical care time, the who, what, where gets really complex.
These are just a few examples that outline how important it is to understand all of the parameters of the time-based service you are providing. If you have questions, please reach out to [email protected] or [email protected].
Resources:
ASHA (American Speech-Language-Hearing Association)
Novitas: Counting Units for Therapy Codes
Novitas: Critical Care
Medicare’s 8-Minute Rule Therapy: The Ultimate 2025 Guide
2026 CPT page xix: Time