Q: I’m going to work one day a week at another doctor’s office. I’m not credentialed for his third-party plans and he wants to bill the exams I do under his provider number. Is this legitimate and might I be at any risk participating?

A: Yes, it’s legitimate. The ability for a fill-in doctor to see the patients of a regular practitioner is allowed by the appropriate use of the Q5 or Q6 modifiers.

Q5 for Reciprocal Billing
Q5 denotes a reciprocal billing arrangement. The regular doctor may submit the claim and receive payment for covered services (including emergency visits), which are provided by a substitute doctor on an occasional reciprocal basis, if all of the following apply:

  • The regular doctor is unavailable to provide the services.
  • The patient has arranged or seeks to receive the services from the regular doctor.
  • The substitute doctor does not provide the services to Medicare patients for a continuous period of more than 60 days.
  • The regular doctor identifies the services as “substitute doctor services” by entering the appropriate CPT code with the -Q5 modifier (“service furnished by a substitute doctor under a reciprocal billing arrangement”) after each specific procedure code.

Q6 for Locum Tenens
Q6 is used to indicate when there is a locum tenens arrangement. Practices usually use a locum tenens (“deputy” in Latin) doctor when the regular doctor is absent because of vacation, illness, childbirth, business, education, active duty or having left the practice.

The regular doctor may submit the claim and receive payment for covered services (including emergency visits) of a locum tenens doctor who isn’t an employee of the regular doctor, if all of the following apply:

  • The regular doctor is unavailable to provide the services.
  • The Medicare beneficiary has arranged to receive the services from the regular doctor.
  • The regular doctor pays the locum tenens for his/her services on a per diem or similar fee-for-time basis.
  • The substitute doctor does not provide the services to Medicare patients for longer than a continuous period of 60 days.
  • The regular doctor identifies the services as “substitute doctor services” by entering in the appropriate CPT code with the -Q6 modifier (“service furnished by a locum tenens physician”) after each specific procedure code.

Follow the Rules
To ensure you get paid and stay in compliance, you must adhere to Medicare and commercial payer guidelines—and the rules are fairly specific.1

For instance, the period a temp doc may substitute for the regular doctor cannot be more than 60 continuous (not work) days.

There are obligations and responsibilities for both parties during this period. For instance, the regular doctor must bill for the services of the temporary doctor, must put his or her National Provider Identification (NPI) number on all filed claims, and may reimburse the temp doc a fixed amount per diem or similar fee.

Also, the regular doctor is the only one who can break the 60-day period, and can reset the 60-day period by returning to practice and seeing patients one day after the initial 60 days and using the same fill-in doctor.

Meanwhile, the temporary doctor cannot bill Medicare for services within the 60-day continuous period in his or her name or NPI. Also, the temp doc cannot fill in for more than 60 continuous calendar days (unless the regular doctor comes in and resets the 60-day period), and cannot reset the 60-day clock by taking a day off.

The temporary doctor doesn’t have to be enrolled in the Medicare program to see Medicare patients.


Some commercial payers have different rules on the use of a locum tenens doctor—Tricare, the Blues and some Medicaid programs come to mind. Following the rules will protect your practice, protect your patients, protect the temporary doctor and protect your cash flow.

1. Centers for Medicare & Medicaid Services. Chapter 1: General Billing Requirements. In: Medicare Claims Processing Manual. Updated Feb 1, 2013. Available at: www.cms.gov/Regulations-and-Guidance/Guidance/Manuals/downloads/clm104c01.pdf. Accessed Aug 21, 2013