Physical therapy billing units are decided by minutes, not by codes: under Medicare's 8-minute rule the timed minutes of every timed code in the visit are added together and billed in 15-minute units, with a unit allowed once at least 8 minutes are documented, and untimed codes are one unit each regardless of time. Most small clinics count it right most of the time and lose a unit on the visits where two timed codes split the minutes. This page states the rule as CMS publishes it, works three visits through, separates the untimed codes, and lists the counting mistakes that cost a unit or invite an audit. The free billing units worksheet on this site does the arithmetic on any visit.
The rule as CMS states it
Medicare's claims processing manual, chapter 5, sets it out: for timed codes measured in 15-minute units, the total timed minutes in the visit decide the units. One unit is billed for 8 to 22 minutes, two for 23 to 37, three for 38 to 52, four for 53 to 67, and each further 15 minutes adds one. The minutes are totalled across the timed codes first, then the units are assigned to the codes by the minutes spent on each, with the code that had the most minutes taking any unit the remainder earns.
Three visits worked through
A visit with 40 timed minutes: 40 falls in the 38 to 52 band, three units. Split 25 minutes of therapeutic exercise and 15 of manual therapy, the exercise takes two units and the manual therapy one. A visit with 20 timed minutes: one unit, however the minutes were split, and the second code is not billed as a unit of its own. A visit with 53 timed minutes: four units, and a visit with 52 is three; the one minute is the difference the note has to document. The worksheet on this site returns the units for any total.
The untimed codes, counted separately
An evaluation, a re-evaluation, a hot or cold pack and the other service-based codes are billed as one unit each regardless of the minutes spent, and their minutes do not join the timed total. The visit's units are the timed units plus the untimed codes, which is the second figure the worksheet returns. Adding an untimed code's minutes to the timed total is the commonest way a clinic bills a unit it did not earn.
The counting mistakes that cost a unit or invite an audit
Counting units per code instead of on the total, which either over-bills or under-bills the split visits. Adding untimed minutes to the timed total. Billing a unit for a timed code with fewer than 8 minutes on its own when the total did not earn the extra unit. And documenting the total but not the minutes per code, which is what an auditor asks for. The plan of care and the documentation Medicare's benefit policy manual describes are what the count rests on; the register keeps the units per claim so a payer's question a year later is answered from the record.
Questions people ask about physical therapy billing units
How many billing units is a 45-minute physical therapy visit?
If all 45 minutes are timed codes, three units, because 45 falls in the 38 to 52 band. If 15 of those minutes were an untimed evaluation, the timed total is 30, two units, plus the evaluation as one unit.
Do commercial payers use the 8-minute rule?
Some follow Medicare's total-time method and some count units per code with a midpoint rule. The contract or the payer's policy says which; the worksheet on this site states the method it uses so you can compare.
Can I bill two timed codes with 10 minutes each?
Under the 8-minute rule the total is 20 minutes, one unit, assigned to one of the codes. The second code is documented but does not earn a separate unit.
Where is the 8-minute rule published?
In the Medicare Claims Processing Manual, chapter 5, section 20.2, which this page cites. The benefit policy manual's chapter 15 covers the documentation and the plan of care behind the claim.
Sources
- Medicare Claims Processing Manual, chapter 5, section 20.2: the 8-minute rule and the unit table for timed therapy codes
- Medicare Benefit Policy Manual, chapter 15, section 220: covered outpatient rehabilitation therapy services and their documentation
- 42 CFR 410.60, Outpatient physical therapy services: conditions for coverage, including the plan of care