The Q6 Modifier: Medicare Locum Tenens Rules
As a locums dermatologist, you’ll eventually hear about the Q6 modifier. It’s a billing shorthand used for Medicare patients that allows a clinic to bill for your services under a permanent doctor’s NPI.
Technically called a Fee-for-Time Compensation Arrangement, it lets the clinic keep its revenue moving while a physician is away (or even permanently vacated) without the 3-month headache of enrolling you in every insurance plan for a short stint.
To make use of this modifier, you generally have to meet 4 criteria:
Be an independent contractor (not a W2 employee).
Coverage cannot exceed 60 days (more on this below).
Be a physician (good job, this one’s already in the bag).
Bill under the regular physician's NPI with the Q6 modifier attached. The clinic must still keep a record of your NPI linked to every service you provided.
The 60-Day Clock (And How to Reset It)
The most critical factor to understand is the timeline. Medicare limits locum tenens billing with the Q6 modifier to 60 continuous calendar days per covered physician’s absence.
A common misconception is that this 60-day limit applies to the clinic as a whole. It doesn't. It’s tied to the specific doctor you're covering. If you're filling in for Dr. Luckett, your Q6 clock starts the first day you see patients in their absence and stops 60 calendar days later. Taking a week off doesn't "pause" the clock.
If the regular physician returns and sees patients for even one day, the 60-day clock resets.
The Risk of Non-Compliance
Before you start an assignment, it's worth touching base with the clinic’s billing team for clarification on how they’re handling your claims. Billing beyond the 60-day window with the Q6 modifier is non-compliant.
The issue here is that while claims might still pay out initially, they carry a high risk of a post-payment audit and recoupment (where the insurer forces the clinic to pay the money back). If your pay is tied to collections, a recoupment caught in a future audit could potentially lead to the clinic seeking a refund from you. Remember, CMS requires "Fee-for-Time" (daily/hourly) pay for Q6; if your contract is purely percentage-based, you might be in a gray area regarding Q6 eligibility.
What Happens After Day 60?
If you expect to work at the same site beyond the two-month mark, you generally have two options to stay compliant:
Cover a different physician: If another doctor in the group is legitimately absent, you can start a separate 60-day clock under their NPI.
Full Credentialing: You can complete the formal enrollment process to bill under your own NPI. As you likely know, this can take months, so it’s a conversation to have with the clinic well before day 45.
Commercial Payers
While Medicare is strict about the 60-day rule, commercial payers vary widely. Some follow Medicare's lead, while others have entirely different credentialing requirements for locums. Don't assume that because you’re "cleared" for Medicare patients under Q6, you’re cleared for every private PPO.
Disclaimer: I’m a dermatologist, not a healthcare attorney or a professional billing consultant. The info in this post is based on my research and understanding of current rules, but it shouldn't be taken as formal legal or billing advice. Since policies change and payer rules vary, you should always consult a qualified healthcare attorney or billing expert regarding your specific situation and contracts.
