Q6 modifier in medical billing: guidelines, usage and examples

A physician’s vacation, medical leave, military obligation, or sudden departure does not stop scheduled patient care. Practices often bring in a temporary physician so patients can still be seen. The clinical handoff may be straightforward, but Medicare billing is not simply a matter of submitting the substitute physician’s work under the regular physician’s name.

The Q6 modifier is the Medicare billing indicator for qualifying services furnished by a substitute physician under a fee-for-time compensation arrangement. Many teams still call it a locum tenens modifier, but CMS changed the formal terminology in 2017. Q6 has specific conditions, a 60-day limit, and a different purpose from Q5 reciprocal billing.

What the Q6 modifier means

CMS describes Q6 as the modifier for a service furnished under a fee-for-time compensation arrangement by a substitute physician. The current Medicare Claims Processing Manual also extends the modifier to certain substitute physical therapist services furnished in a health professional shortage area, medically underserved area, or rural area. For physician practices, the core concept is temporary coverage: the regular physician is unavailable, a substitute furnishes the covered services, and the payment arrangement meets Medicare’s fee-for-time rules.

CMS uses fee-for-time compensation arrangement for coverage paid on a per diem or similar time-based basis. Q6 is therefore not a general modifier for every covering physician or temporary staffing arrangement.

Q6 modifier Medicare requirements

The Q6 modifier requirements should be checked before the first claim is released. Under the Medicare rules, the arrangement generally needs to satisfy all of the following conditions:

• The regular physician is unavailable to provide the services.
• The Medicare beneficiary arranged or sought to receive the services from the regular physician.
• The regular physician or group pays the substitute on a per diem or similar fee-for-time basis.
• The substitute does not provide covered services to the regular physician’s Medicare patients over a continuous period longer than 60 days, subject to the Armed Forces active-duty exception.
• The claim identifies the qualifying substitute physician service by appending modifier Q6 to the procedure code.

Medicare counts the continuous period from the first day the substitute provides covered services to the regular physician’s Part B patients. Days without encounters do not stop the clock. The period ends when the regular physician returns, after which a new period can begin. CMS provides an exception when the regular physician is called to active duty in the Armed Forces.

Q6 is not the same as Q5

Q5 and Q6 both deal with temporary coverage, but they represent different billing arrangements. Q5 is used for a reciprocal billing arrangement, where physicians cover for one another on an occasional reciprocal basis. Q6 is used for a fee-for-time compensation arrangement in which the substitute is paid on a per diem or similar time-based basis.

CMS changed the formal terminology from ‘locum tenens’ to fee-for-time compensation arrangements in Change Request 10090. The older phrase remains common, but billing staff should choose the modifier from the actual arrangement, not the label used by a staffing agency or scheduler.

How to bill the Q6 modifier

Substitute physician billing should be checked before charge entry. Confirm the regular physician’s absence, coverage dates, how the substitute is paid, and whether Medicare enrollment or reassignment rules affect the claim. Normal coverage, documentation, coding, and medical-necessity requirements still apply.

For a qualifying Medicare professional claim, the regular physician or eligible group bills the covered service with Q6 after the CPT or HCPCS code. On Form CMS-1500, CMS places the modifier in item 24D; the electronic claim carries equivalent service-line information. Keep a record of the substitute’s services and NPI for audit support.

CMS determines payment as though the regular physician furnished the service, but the practice still needs records showing who actually rendered care and when.

Examples of when Q6 may apply

Short-term vacation coverage

A family physician is away for two weeks and pays a substitute physician a daily rate. Established patients continue through the regular practice. If the Medicare requirements are met, qualifying services may be billed with Q6.

Coverage that extends beyond 60 days

If the regular physician is absent for more than two months, weekends and days without Medicare visits do not restart the continuous period. After the 60-day limit, Q6 cannot simply continue unless an exception applies; the billing arrangement must change appropriately.

Temporary replacement after a physician leaves a group

CMS also allows a medical group to use the fee-for-time provisions for a temporary replacement after a physician leaves the group, subject to group requirements and the 60-day limit. Credentialing and billing teams should confirm whether the substitute has reassigned Medicare payment rights to the group.

Common Q6 modifier billing errors

Most Q6 errors come from treating temporary coverage as a scheduling issue instead of a billing arrangement with its own rules.

• Using Q6 whenever one physician covers another without confirming the fee-for-time arrangement.
• Confusing Q6 with Q5 reciprocal billing and applying the wrong temporary-coverage modifier.
• Restarting the 60-day count after weekends or days when the substitute did not see a Medicare patient.
• Failing to retain the substitute physician’s NPI, service dates, and records supporting the arrangement.
• Continuing to use Q6 after the regular physician returns or after the allowable continuous period ends.
• Assuming a Medicare Advantage or commercial payer automatically follows Original Medicare Q6 rules without checking that payer’s policy.

If the substitute is already enrolled with, employed by, or has reassigned benefits to the group, Q6 may not be the correct path. Review enrollment structure and payer instructions before submission.

How RCMGen handles substitute physician billing

Temporary coverage touches scheduling, credentialing, coding, enrollment, and claims. RCMGen’s physician billing and clinic RCM services connect those steps so billing teams can track when the substitute arrangement begins and ends.

Our broader medical billing services include coding, modifier review, professional claim submission, denial management, and A/R follow-up. For Q6 claims, the billing structure is confirmed before submission instead of being treated as a last-minute edit.

The same principle applies across our revenue cycle management services: payer-specific claim scrubbing should validate the service, modifier, provider information, and documentation context together. A technically clean Q6 claim can still be wrong if the underlying arrangement does not qualify.

Frequently asked questions about the Q6 modifier