Overview
Modifier Q6 is the Medicare modifier for what used to be called locum tenens billing. Its CMS descriptor reads "service furnished under a fee-for-time compensation arrangement by a substitute physician or by a substitute physical therapist furnishing outpatient physical therapy services in a health professional shortage area, a medically underserved area, or a rural area", and chapter 1, section 30.2.11 of the Medicare Claims Processing Manual sets the conditions. The practice it describes is old: a physician who is away for illness, vacation, continuing education or similar reasons retains a substitute, often an independent contractor with no practice of their own, and bills for the substitute's services as if they were their own.
The regular practitioner may submit the claim, and receive payment on assigned claims, when four conditions hold. The regular practitioner is unavailable; the beneficiary sought care from the regular practitioner; the regular practitioner pays the substitute per diem or on a similar fee-for-time basis; and the substitute does not serve the regular practitioner's Medicare patients for a continuous period longer than 60 days, unless the regular practitioner has been called to active duty in the Armed Forces. The 60 days run from the first day the substitute furnishes covered services and continue through days with no services until the regular practitioner returns. Services after day 60 must be billed by the substitute under their own NPI or reassigned.
Since June 13, 2017, under the 21st Century Cures Act, physical therapists in private practice can use the same arrangement for outpatient physical therapy furnished in a health professional shortage area, a medically underserved area or a rural area. Medical groups can also bill Q6 services for a member who is away, or for a member who has left the group and is being temporarily replaced, provided the substitute has not reassigned benefits to the group; the group keeps a record of each service with the substitute's NPI and identifies the regular practitioner by NPI on the claim line.
Entering Q6 is a certification. The regular practitioner or group certifies that the services were furnished by the substitute identified in a record available for inspection and that the practitioner is entitled to bill them, and the manual warns that false certifications can lead to civil, criminal or administrative penalties, including revocation of billing privileges. Payment is calculated as though the regular practitioner furnished the service. Q6 is distinct from Q5, which reports services under a reciprocal billing arrangement between practitioners who cover for each other without fee-for-time pay.
Worked example
A rural family physician takes medical leave from March 3 to May 20. A substitute physician paid a daily rate begins seeing her Medicare patients on March 5. The practice bills those visits under the regular physician's NPI with modifier Q6 through May 3, the 60th day of the continuous period that began March 5, and keeps a log of each visit with the substitute's NPI. Visits from May 4 until the physician returns are billed under the substitute's own NPI.
Look it up in CMS data
Free reference pages and tools rebuilt from the current CMS release files, for looking up the CMS data behind this term.
Frequently asked questions — Modifier Q6 (Fee-for-Time Substitute Practitioner)
What is the 60-day limit for Q6 billing?
A substitute may not furnish services to the regular practitioner's Medicare patients for a continuous period longer than 60 days. The period starts on the substitute's first day of covered services and runs until the regular practitioner returns; services after day 60 are billed by the substitute. Active-duty military service is the exception.
What is the difference between modifiers Q5 and Q6?
Q6 reports a substitute paid on a per diem or other fee-for-time basis. Q5 reports services under a reciprocal billing arrangement, where practitioners cover for each other without that kind of payment. Both let the regular practitioner bill, with different conditions in chapter 1 of the Claims Processing Manual.
Can a physical therapist bill with Q6?
Yes, since June 13, 2017, for outpatient physical therapy furnished by a substitute physical therapist in a health professional shortage area, a medically underserved area or a rural area, under the 21st Century Cures Act.
Which NPI goes on a Q6 claim?
The regular practitioner's. For group claims the regular physician or therapist is identified by NPI on the claim line, and the group keeps a record of each service with the substitute's NPI, available to the MAC on request.
Disclaimer
This glossary entry is operational reference for revenue-cycle and medical-billing professionals. It is not legal, clinical, or contractual advice. Industry benchmarks cite named public sources where available; always verify against the current guidance from the authority body before relying on a number in a contract, policy, or compliance filing.