First, what incident-to actually is, in plain terms. When an advanced practice provider (a nurse practitioner, physician assistant, or other qualified clinician) sees a patient, the practice has two ways to bill Medicare for that visit. It can bill under the APP's own number, which Medicare pays at 85 percent of the physician fee schedule. Or, if a specific set of conditions is met, it can bill the same visit "incident to" a physician, under the physician's number, which Medicare pays at the full 100 percent. That 15-percentage-point difference is the entire reason incident-to exists as a billing strategy, and it is also why it draws audit attention. None of this is a judgment about the APP's skill; the APP is providing real, independent clinical care. Incident-to is purely a billing construct about whose number the claim goes out under and what it pays.

A note on terminology: this chapter says "APP" to cover nurse practitioners, physician assistants, clinical nurse specialists, certified nurse-midwives, certified registered nurse anesthetists, anesthesiologist assistants, and other qualified non-physician practitioners. The incident-to rules apply to the billing arrangement, not to any one profession, so read "APP" inclusively throughout.

The Four Requirements for Incident-To Billing

All four of the following must be true for an incident-to claim to be compliant:

1. The care must be integral to the physician's own treatment plan. The billing physician (not just any physician in the group, in most interpretations the physician who established the plan) must have personally seen the patient, diagnosed the problem, and set the plan of care that the APP is now carrying out. "You" here means that billing physician: it is your established plan the visit must be continuing.

2. The supervising physician must be in the same office suite. For office-based incident-to billing, the physician must be present in the same office suite as the APP during the time of service, not just in the building or available by phone. "Same suite" means physically present and immediately available if needed.

3. This particular visit must be a continuation, not a new problem. Requirement 1 is about the relationship (you established the overall plan). This requirement is about the specific encounter being billed: it has to be a follow-up for a problem already evaluated and under an existing plan. Even with a long-standing patient, the moment a genuinely new problem comes up, or the plan needs a substantive change that amounts to a fresh physician evaluation, that part of the visit is no longer incident-to. The distinction is relationship (requirement 1) versus this specific encounter (requirement 3).

4. The service must be included in the physician's standard of care. The APP's service must be the type of service that is typically provided as part of physician care in that practice setting.

The new-problem trap
This is where practices most often go wrong. An established patient comes in for an APP-managed follow-up, and partway through raises a new complaint that the physician has never evaluated. Billing that whole visit incident-to, under the physician's number at 100 percent, is non-compliant, because no physician plan exists for the new problem. So what do you actually do? You have two clean options. First, bill the visit under the APP's own number at 85 percent; this is always allowed and is the simplest correct answer. Second, if the supervising physician is available and personally steps in to evaluate the new problem and set the plan during that same visit, document that involvement and the encounter can be billed under the physician. What you cannot do is leave the new problem in an APP-only visit and still bill it incident-to. When in doubt, bill under the APP: you lose 15 percent, not your compliance.
Two quick examples
Example one, incident-to is fine: you saw Mr. Lopez last month, diagnosed hypertension, and started a medication. Today your NP sees him for a scheduled blood-pressure recheck, confirms the plan is working, and makes no major change, with you present in the suite. This is a textbook incident-to visit: bill under your number at 100 percent. Example two, incident-to does not apply: the same NP sees Mr. Lopez for that recheck, but he also mentions new chest pain. The NP works it up. There is no physician plan for chest pain, so that visit is billed under the NP's number at 85 percent, unless you personally step in, evaluate the chest pain, and document it.

Incident-To Does Not Apply in Hospital Settings

Incident-to billing is an outpatient concept only. In hospital inpatient and outpatient hospital settings, APPs always bill under their own NPI at their own rate, regardless of physician supervision. This is a common misunderstanding that leads to incorrect claims in practices that operate across both settings.

The State Scope-of-Practice Interaction

Incident-to billing is a Medicare billing rule, not a clinical scope-of-practice rule. An APP may be legally authorized under state law to practice independently, but that does not change whether a given visit qualifies for incident-to billing under Medicare's rules. The supervision requirement for billing purposes is separate from the clinical authority requirement under state law.

Documentation Best Practice

Document three things and incident-to becomes defensible: the physician's initial evaluation and the plan of care that was established, the APP's follow-up note explicitly referencing that ongoing physician-established plan, and the supervising physician's presence in the office suite during the visit. If your workflow has the physician review and co-sign APP notes, do it consistently, not selectively. A clean audit trail showing the physician's initial evaluation and the continuity of the established plan is your best protection if the billing is ever reviewed. And if any element is missing for a given visit, the safe move is to bill under the APP.

Sources and Further Reading for This Chapter

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