CQ and CO modifiers: assistant services and the payment difference
Which services carry the CQ or CO modifier, what the 10% exception covers, and the arithmetic of a payment at 85%.
Under US Medicare Part B, a service billed with the CQ or CO modifier is paid at 85% of the fee schedule amount. The CQ and CO modifiers mark outpatient therapy provided in whole or in part by a therapy assistant. CQ is for a physical therapist assistant (PTA), and CO is for an occupational therapy assistant (OTA).
The CQ and CO modifiers change what a unit is paid. Units and productivity percentages stay the same.
What the CQ CO modifier means
Under US Medicare, the CQ modifier is for outpatient physical therapy provided in whole or in part by a PTA. The CO modifier is for the same in occupational therapy, provided by an OTA.
Two dates set the rule:
- 1 January 2020: the CQ and CO modifiers became required, when applicable, on claims with dates of service from that day.
- 1 January 2022: services with the CQ and CO modifiers have been paid at 85% of the otherwise applicable fee schedule amount from that day.
Both are US Medicare rules. Other payers, in the US and elsewhere, set their own rules for services that assistants deliver.
The 85% payment, worked out
The reduction is 15% of the fee schedule amount for each unit that carries the CQ or CO modifier. The figures below use an example amount of 30 a unit. That figure is for the arithmetic only and is not a real Medicare rate.
| Example | Without CQ or CO | With CQ or CO (85%) | Difference |
|---|---|---|---|
| 1 unit at 30 | 30.00 | 30 × 0.85 = 25.50 | 4.50 |
| A visit of 3 units | 3 × 30 = 90.00 | 90 × 0.85 = 76.50 | 13.50 |
| A week of 100 units | 100 × 30 = 3,000.00 | 3,000 × 0.85 = 2,550.00 | 450.00 |
The 85% rate also shows how many units it takes to match a payment. One hundred units with the CQ or CO modifier pay the same as 85 units without it. To match the payment of 100 units without the modifier, a clinic would need 100 ÷ 0.85 = 117.6 units with it.
That figure describes payment only. It says nothing about how many patients an assistant can safely see, and a clinic's caseload decisions rest on clinical judgment.
The 10% exception
Under US Medicare, payment for an assistant's part of a service is not reduced when it is 10% or less of the service's total minutes. Above 10%, the exception no longer covers it, and the CQ or CO rules apply.
Example: a timed service of 40 minutes, delivered mostly by the physical therapist. Ten percent of 40 minutes is 4 minutes.
| PTA minutes (example) | Share of the 40 minutes | Covered by the 10% exception? |
|---|---|---|
| 3 | 3 ÷ 40 = 7.5% | Yes |
| 4 | 4 ÷ 40 = 10.0% | Yes (not over 10%) |
| 5 | 5 ÷ 40 = 12.5% | No |
One minute separates the second row from the third. The minutes each clinician delivered therefore need to be recorded as they happened, by both the therapist and the assistant.
The final unit
CMS adds a rule for the last unit of a service. Suppose the PT or OT provided more than half of the final unit's minutes on their own. That final unit is then billed without the CQ or CO modifier.
Ask your billing team for the full method.
The unit count stays the same
The CQ and CO modifiers leave the US Medicare 8-minute rule as it is. A day's timed minutes bill 1 unit from 8 to 22, 2 units from 23 to 37, and 3 units from 38 to 52.
The day's total timed minutes for the patient set the number of units. When more than one 15-minute timed code is given in a single day, those minutes are added together first.
Example: a patient receives 38 timed minutes in one day, shared between a PT and a PTA. The day bills 3 units, whoever delivered the minutes. The CQ modifier then marks which of those units are paid at 85%.
The 8-minute rule guide shows how units are shared between several timed codes in a day.
Assistant productivity
A productivity percentage is built from minutes, hours or credited units, and the CQ and CO modifiers change none of them. A PTA who delivers 380 treatment minutes in a 450-minute paid day is at 380 ÷ 450 = 84.4%. That percentage is the same whether every unit carries CQ or none do.
The payment difference sits with the clinic's revenue, outside the productivity figure. An assistant who wants to know how their target was set can ask whether payment entered the calculation. Our COTA and PTA targets guide explains when a higher assistant target is fair, and how to test it with your own minutes.
CQ hours and a billable-hours target
The billable hours calculator counts hours, so an hour of CQ or CO services counts as a full hour in it. It takes your available hours, the billable hours you have so far, your target billable rate and your typical appointment length. It shows the hours the target requires, your current rate, the hours you are short or ahead, and the appointments that would close the gap.
Example: 40 available hours in a week, 30 billable hours so far, an 85% target and 30-minute appointments.
- Hours required: 40 × 0.85 = 34.0.
- Current billable rate: 30 ÷ 40 = 75.0%.
- Hours short: 34.0 − 30 = 4.0.
- Appointments to close the gap: 4.0 × 60 ÷ 30 = 8.
Those 30 billable hours count the same whether every hour carries CQ or none does. The guide to the billable minutes needed to hit target covers the same arithmetic in minutes.
Questions to ask your billing team
- Which of my services carry the CQ or CO modifier, and how is that decided for each unit?
- How are the therapist's and the assistant's minutes recorded when we share a service?
- How does the 10% exception show up in the notes?
- Do any of our other payers have their own rules for assistant services?
This post explains US Medicare rules in general terms and gives no billing, coding, legal or employment advice. The billing team where you work, each payer's own rules and current CMS guidance decide every claim.