If your clinic bills Medicare, the 8-minute rule decides how many units you can bill for timed therapy codes. Many commercial payers follow it too. Applied wrongly, it either leaves money on the table or overbills, which is worse. Here’s how it works, with the examples that trip people up.
Which codes it applies to
The rule covers timed codes, where each unit represents 15 minutes of one-on-one service, such as 97110 (therapeutic exercise), 97112 (neuromuscular re-education), 97116 (gait training), 97140 (manual therapy) and 97530 (therapeutic activities).
It doesn’t apply to untimed (service-based) codes, which are billed once per visit regardless of time. Evaluations (97161 to 97163), re-evaluations (97164) and unattended electrical stimulation (G0283 for Medicare, 97014 for many other payers) are examples. Their minutes don’t count toward timed units.
Step 1: add up the total timed minutes
Add the minutes of every timed service in the visit, then convert the total to units:
| Total timed minutes | Units you can bill |
|---|---|
| 8 to 22 | 1 |
| 23 to 37 | 2 |
| 38 to 52 | 3 |
| 53 to 67 | 4 |
| 68 to 82 | 5 |
Fewer than 8 total timed minutes means no timed units can be billed.
Step 2: assign the units to codes
Each full 15 minutes of a service earns that code one unit. If minutes are left over, any remaining units go to the services with the most leftover minutes.
Example: 33 minutes of 97110 and 7 minutes of 97140. Total: 40 minutes, so 3 units.
97110 gets 2 units for its first 30 minutes, with 3 minutes left over. 97140 has 7 minutes. The third unit goes to the service with more leftover time, 97140. Bill 97110 × 2 and 97140 × 1.
Example: 7 minutes each of 97110, 97140 and 97530. Total: 21 minutes, so only 1 unit.
All three have equal time, so you bill one unit of one code. Billing one unit of each would be three units for 21 minutes, which is overbilling.
Commercial payers may use a different method
Some commercial payers apply the rule per code instead: each service needs at least 8 minutes on its own to bill a unit. Under that method, the 7-minute 97140 above wouldn’t be billable at all. Check each payer’s policy, and set your billing rules per payer rather than one rule for everyone.
Other Medicare therapy rules to bill alongside it
- GP modifier on every physical therapy line.
- CQ modifier when a PT assistant furnishes all or part of the service. It changes the payment amount.
- KX modifier once the patient’s therapy costs for the year pass Medicare’s threshold, with documentation that continued care is medically necessary.
- NCCI edits: some code pairs, such as 97140 and 97530, need a properly supported modifier like 59 or XU to both be paid.
Document the minutes
Record total timed minutes and the minutes for each service in the daily note. If an auditor can’t match the units to the time in the note, the extra units get taken back.
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