The 8-minute rule, explained without the jargon
The unit table, how units are shared between timed codes, and four worked examples.
The 8-minute rule is the US Medicare Part B method for turning minutes on timed codes into 15-minute billing units. You bill one unit for 8 to 22 timed minutes, then one more unit for each further 15 minutes.
Most mistakes happen after the table. A patient with more than one timed code in a day needs the units shared between the codes.
The Medicare 8-minute rule table
Under US Medicare Part B, the total timed minutes for one patient on one calendar day set the number of units.
| Total timed minutes | Units |
|---|---|
| 0 to 7 | 0 |
| 8 to 22 | 1 |
| 23 to 37 | 2 |
| 38 to 52 | 3 |
| 53 to 67 | 4 |
| 68 to 82 | 5 |
| 83 to 97 | 6 |
| 98 to 112 | 7 |
| 113 to 127 | 8 |
The first unit needs 8 minutes and each unit after it needs another 15. The pattern stays the same above two hours, so 128 minutes is 9 units. Eight minutes is over half of a 15-minute unit. To rebuild the table from memory, start at 8 and add 15 for each unit: 8, 23, 38, 53. So 37 minutes is two units, and three starts at 38.
Timed codes: total first, then share the units
Under Medicare you don't apply the table to each code on its own. You add up the minutes of every 15-minute timed code the patient received that calendar day. Then you apply the table once and share the units between the codes.
The sharing has two steps:
- Each code gets one unit for every full 15 minutes it has.
- Any units still left go to the codes with the most minutes left over.
Example 1: two codes
A patient receives 20 minutes of therapeutic exercise and 15 minutes of manual therapy. The total is 35 timed minutes, which is 2 units. Therapeutic exercise has one full 15 minutes (5 left over) and manual therapy has one (none left over). Both units are used in step 1, so each code bills one unit.
Example 2: three codes
Now 20 minutes of therapeutic exercise, 10 of manual therapy and 8 of neuromuscular re-education. The total is 38 minutes, which is 3 units. In step 1, therapeutic exercise takes one unit and has 5 minutes left over. Manual therapy (10 minutes) and neuromuscular re-education (8 minutes) have no full 15 minutes, so they take nothing yet. In step 2, the two remaining units go to the codes with the most minutes left: manual therapy (10) and neuromuscular re-education (8). Each code bills one unit.
Example 3: 22, 13 and 9 minutes
Twenty-two minutes of therapeutic exercise, 13 of manual therapy and 9 of neuromuscular re-education make 44 minutes, which is 3 units. Therapeutic exercise takes one unit in step 1 and has 7 minutes left over. The two remaining units go to manual therapy (13 left) and neuromuscular re-education (9 left). Each code bills one unit. Manual therapy's 13 minutes are less than a full 15, so they earn one unit in step 2 and no more.
Example 4: a code with under 8 minutes
Thirty-three minutes of therapeutic exercise and 7 of manual therapy make 40 minutes, which is 3 units. Therapeutic exercise takes two units in step 1 (30 minutes) and has 3 left over. The third unit goes to manual therapy, because its 7 minutes left over are more than 3. Therapeutic exercise bills two units and manual therapy bills one.
A code with 7 minutes or less still counts toward the day's total and can earn a unit. "Under 8 minutes bills nothing" is true of the day's total, not of a single code.
| Example | Minutes per code | Total | Units | Units per code |
|---|---|---|---|---|
| 1 | 20, 15 | 35 | 2 | 1, 1 |
| 2 | 20, 10, 8 | 38 | 3 | 1, 1, 1 |
| 3 | 22, 13, 9 | 44 | 3 | 1, 1, 1 |
| 4 | 33, 7 | 40 | 3 | 2, 1 |
The 8 minute rule calculator
The 8 minute rule calculator does both steps. Enter the minutes for up to four timed codes. It shows the total units, the units for each code, and how many more minutes would reach the next unit. When two codes have the same minutes left over, the calculator gives the unit to the code with more minutes in total. Your billing system or payer may handle a tie differently, so check a tied result before you sign the note.
It checks the Medicare arithmetic only. You decide which codes are timed and which payer rules apply.
Untimed codes stay out of the total
Only 15-minute timed codes go into the day's total. Codes billed per service rather than per 15 minutes are untimed, and their minutes stay out of it. Adding untimed minutes to the timed total raises the unit count for minutes that the rule doesn't cover. If you aren't sure which of your codes are timed, ask your billing team before you total the day.
When a payer counts each code separately
Some commercial payers count each code separately, following an AMA CPT time convention, instead of totaling the timed minutes first. Check each payer's policy.
The two methods can bill a different number of units for the same visit. In Example 4, the 7 minutes of manual therapy earn a unit under Medicare because they count toward the day's total. When a payer counts each code on its own, a code has to earn its units from its own minutes.
One caseload can include payers that use each method. The 8-minute rule is the US Medicare Part B method, and payers outside the US have their own.
How the 8-minute rule affects productivity
Some employers measure productivity in billed units multiplied by 15 instead of actual minutes. Then the rule changes your productivity figure as well as the bill.
A 23-minute treatment bills 2 units, which is 30 credited minutes. A 22-minute treatment bills 1 unit, which is 15. One minute of treatment makes 15 minutes of difference in your credit. Treatment length is a clinical decision, and the credit gap is no reason to change it. The units to minutes conversion guide shows the gain or loss at each threshold.
Habits that keep the minutes right
- Record actual minutes, not planned minutes. If a session was cut short, write the time it ran.
- Keep timed and untimed codes apart in your notes so the timed total is clear to anyone who reviews it later.
- Ask your billing team which payers count each code separately.
- Don't round up to reach a threshold. A treatment that ran 22 minutes is a 22-minute treatment, even though the 23rd minute would add a whole unit.
This guide is general information about the US Medicare rule. It is not billing, coding or legal advice. Your billing department, your payer's rules and current CMS guidance decide any claim.