Codes 101: The 8-Minute Rule & Time-Based CPT Codes

For many practitioners, billing codes are not why they became physical therapists. But the reality of providing therapy services means having to bill insurance. For federally funded plans like Medicaid and Medicare, physical therapy billing is directly tied with the 8-Minute Rule. 

What Is the 8-Minute Rule?

The 8-Minute Rule is the method of calculating the number of billable units PTs should bill Medicare or Medicaid for therapy services rendered to a patient on a particular date of service. In order to fully understand the 8-Minute Rule, you must first understand what constitutes as billable time, specifically the difference between service-based and time-based CPT codes.

Service-Based vs Time-Based CPT Codes

Service-based CPT codes are for untimed services like unattended electrical stimulation (97014) or physical therapy evaluation (97161, 97162, or 97163). During these services, either no direct therapy is taking place or the service does not require constant attendance. As a result, these services can only be billed once, regardless of the amount of time spent performing this service.

On the other hand, time-based CPT codes are for services where a PT has direct contact, or is in constant attendance, with the patient during the service. For example, types of time-based CPT codes include:

  • Manual therapy (97140),
  • Ultrasound (97035),
  • Therapeutic exercises (97110), and
  • Manual electrical stimulation (97032). 

These one-on-one services allow for billing in 15-minute increments. 

How to Calculate Billable Units

To calculate the number of billable units, the total time for time-based services is added together for a particular date of service. This total time is then divided by 15. The end value is the number of billable units. 

The following is an 8-Minute Rule reference chart of the number of minutes per billable unit: 

  • 8–22 minutes = 1 unit
  • 23–37 minutes = 2 units
  • 38–52 minutes = 3 units 
  • 53–67 minutes = 4 units
  • 68–82 minutes = 5 units
  • 83–97 minutes = 6 units
  • 98–112 minutes = 7 units
  • 113–127 minutes = 8 units 

Billable Units Example

On a particular date of service, the following occurred: 10 minutes of ultrasound, 15 minutes of manual therapy, and 8 minutes of therapeutic exercises, plus 15 minutes of physical therapy evaluation. 

10 min. + 15 min. + 8 min. = 33 min./15 = 2 billable units (time-based)

Because the physical therapy evaluation qualifies as service-based, these 15 minutes equate to 1 billable unit. 

Total billable units = 3

Note: For remainders of eight minutes or more, you can bill an additional unit. For seven minutes or fewer, these minutes cannot be billed. 

Mixed Remainders

In situations where the remainder is more than eight minutes but comes from two or more therapy services, these minutes may be added together to equal one additional unit. Use the CPT code of the largest remainder for billing. 

For example, if there is a remainder of 4 min. manual therapy, 2 min. ultrasound, and 2 min. therapeutic exercises, then these values may be added together for an additional unit billed to manual therapy (the largest remainder). 

4 min. + 2 min. + 2 min. = 8 min. = 1 billable unit

Common Mistakes

When using the 8-Minute Rule, common mistakes include the following:


  • Including service-based time with time-based services. 


Service-based time must be counted separately as it can only count for one billable unit, regardless of how much time was spent. It should not be added in with the time-based services.


  • Confusing the amount of services with the number of units.


On the 8-Minute Rule chart, 8–22 minutes equals 1 unit. Regardless if one service takes 22 minutes or two services equal 20 minutes (10 mins. manual therapy + 10 min. ultrasound), both only equal 1 billable unit each. 


  • Assigning codes before looking at total treatment time. 


By calculating the total time for time-based services, you may have a qualifying remainder amount that could equal an additional unit. If codes are assigned beforehand without looking at the total, the additional billable unit could be lost. 

Create an account with MeyerPT today or contact your personal account manager at 1.866.528.2144 for more information.


Andrus, Brooke, and Erica McDermott. “The 8-Minute Rule: What It Is and How It Works in WebPT.” WebPT, 13 Sept. 2018,

Harmon, Roy. “Everything You Need to Know About the 8-Minute Rule.” Pediatric Occupational, Speech & Physical Therapy Blog, 21 June 2018,

Jannenga, Heidi. “Physical Therapy And The Medicare 8 Minute Rule.” WebPT, 11 Jan. 2019,

“Know How to Apply the Eight-Minute Rule for Time-Based Outpatient Therapy Codes.” HCPro, 13 Jan. 2012,