American College of Physicians: Internal Medicine — Doctors for Adults ®


Billing services provided by moonlighting residents

From the November ACP-ASIM Observer, copyright 2001 by the American College of Physicians-American Society of Internal Medicine.

By Brett Baker

Q: Do residents who moonlight need a Medicare unique physician identification number and a provider identification number?

A: Yes. Residents must enroll in Medicare and receive a unique physician identification number (UPIN) and a provider identification number (PIN) to bill for services outside the scope of their residency program.

The Centers for Medicare and Medicaid Services (CMS), formerly HCFA, says that moonlighting occurs when interns and residents provide medical and surgical services unrelated to their training. Such services are performed in the emergency department of the hospital where they train, outside their training program's facility or in an outpatient setting.

Physicians receive a UPIN when Medicare, through its local carrier, approves their application. The UPIN identifies the referring or ordering physician and appears on line 17 of the HCFA-1500 claim form.

Medicare carriers also issue physicians a PIN when approving physicians' Medicare applications. The PIN identifies the physician who provided services and is also used for tax and payment purposes. Physicians list their PIN in box 24k of a claim to indicate who furnished the service and in box 33 to instruct the carrier who receives payment. (If payment for services goes to a group, you can list a group PIN number in field 33.)

Physicians who move to another state must obtain a new PIN number from the new state's Medicare carrier. Physicians' UPIN, however, remains the same, even if they move to a different carrier jurisdiction.

Q: Does a physician who pays a moonlighting resident an hourly rate to provide office coverage need to identify the resident's PIN on the claim form, even though the physician employer receives the payment?

A: Yes. CMS requires the physician rendering the service to be identified on the claim, whether the rendering physician receives the payment directly or assigns the right to payment to another physician or entity. The moonlighting resident's PIN must be listed in box 24k of the claim form, while the PIN for the physician or group to which residents assign their right to payment must appear in box 33.

Moonlighting residents can reassign to an employer the right to payment for Medicare-covered services only if they are eligible to receive the payment. A moonlighting resident must complete the Medicare application process and receive a UPIN and a PIN to be allowed to reassign the right to payment to an employer.

Medicare enrollment forms and information are available online at You can also contact your Medicare carrier to initiate the enrollment process. Medicare carrier (Part B) contact information is listed by state at

CMS defines reassignment as an assigned payment made to anyone other than the physician or supplier who provided the service. CMS allows physicians to reassign their payment in limited circumstances. Medicare reassignment rules state that carriers can make payments to an employer for services rendered as long as an employer-employee relationship exists that entitles the employer to payment for services provided by the employee.

Q: Can a moonlighting resident ever provide coverage in a physician's office without a UPIN and PIN?

A: Moonlighting residents do not need a UPIN and PIN if they function as a mid-level practitioner, such as a physician assistant or nurse practitioner. The employing physician would be able to bill for the moonlighting resident's services that are "incident to" his or her services.

The Medicare "incident-to" regulations allow employing physicians to bill for patient follow-up visits provided by a mid-level practitioner. Employing physicians, however, must see the patient on the initial visit to make a diagnosis and establish a care plan.

Employing physicians can bill for mid-level practitioner services as long as they provide direct personal supervision. To meet Medicare's definition of direct personal supervision, physicians must be in the same office suite but not necessarily the same exam room as the mid-level practitioner. When supervising, physicians must be immediately available to provide assistance and direction.

Brett Baker is a third-party payment specialist in the College's Washington office. If you have a question about third-party payment or coding issues, contact him at 202-261-4533 or


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