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-GC

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Modifier -GC: Resident service under teaching physician direction

Quick reference

  • Definition: Modifier -GC = “This service has been performed in part by a resident under the direction of a teaching physician.”
  • What you’re certifying: When GC is on the claim, the billing provider is certifying they complied with Medicare teaching-physician requirements for that service.
  • When Medicare expects it: Claims in teaching settings generally must include GC on each service involving resident participation, unless the service is billed under the primary care exception (then GE applies).
  • Key rule behind GC: Medicare pays under the PFS when residents perform the service and the teaching physician is physically present during the critical/key portions (with defined telehealth exceptions for certain Medicare telehealth scenarios).

When to use vs not use

Use -GC when

  • A resident performs any part of a billable service in a teaching setting and the teaching physician meets the Medicare requirements (for E/M or procedures) for participation/presence.
  • You are billing the teaching physician’s NPI for a service where the resident’s work is part of the documented service and the teaching physician’s presence/participation requirements are met.

Don’t use -GC when

  • The service is furnished under the primary care exception (then use GE, not GC).
  • The work was performed by a medical student (Medicare does not pay for services furnished by a medical student as defined in CMS policy, and GC is not the “fix”).
  • The resident service is outside the approved training program context (“moonlighting” rules are separate and Medicare policy specifically describes when resident services may be covered as physician services).

Documentation requirements (what auditors look for)

Teaching physician attestation basics

  • Your documentation needs to demonstrate the teaching physician performed the service or was present during the critical/key portions and participated in management.
  • A generic attestation like “Seen and agree” is commonly cited as insufficient, while a statement describing what the teaching physician did and/or their time/critical involvement is expected.

Examples (from MAC guidance):

  • Acceptable-style example includes a clear statement of time/effort and what the teaching physician did (e.g., managing a hypoxic/hypotensive event and reviewing/confirming the plan).
  • Unacceptable-style example: “I saw the patient and agree with the resident.”

E/M specifics

  • CMS allows teaching physicians to sign/date notes entered by other team members if they demonstrate presence and participation, but the combined record must support medical necessity and the teaching physician’s role.
  • If office/outpatient E/M is selected by total time, count only the time attributable to the teaching physician per CMS rules (not resident-only time).

Surgical/procedural specifics

  • CMS frames billability around teaching physician presence during the critical/key portions of resident-performed services and procedures.
  • Your procedure note should clearly identify: the resident’s role, the key/critical portions, and the teaching physician’s presence (and immediate availability as applicable).

Time-based services (critical care is the big trap)

  • CMS states that for time-based codes, the teaching physician must be present for the time period billed, and you may not add resident-only time to reach time thresholds.
  • Noridian also emphasizes that teaching time doesn’t count toward the teaching physician’s critical care time, and only time with the patient (teaching physician alone or teaching physician + resident together) is countable.

Telehealth note (2026 reality check)

  • CMS telehealth guidance for CY 2026 states teaching physicians may have a virtual presence for purposes of billing services involving residents only for services furnished as a Medicare telehealth service, using real-time audio/video (three-way telehealth) during the key portion.
  • This is separate from “primary care exception” logic; it’s about how presence can be met for certain telehealth services involving residents.

Ophthalmology + ENT scenarios (practical)

Ophthalmology: same-day clinic + procedure

  • If a resident participates in a minor procedure day (e.g., in-office procedure) and the teaching physician meets the teaching-physician requirements, bill the service with GC on the procedure code(s) as applicable and ensure the teaching physician attestation clearly supports presence/participation.
  • If the visit is time-based (common in complex visits), ensure time counted reflects teaching physician time rules.

ENT: endoscopy/procedures with resident involvement

  • When residents perform parts of nasal endoscopy or minor ENT procedures under teaching physician direction, GC is used to indicate resident participation, and the note should specify the teaching physician’s presence for key/critical portions.
  • If two distinct services occur (E/M + procedure), GC is about resident involvement—not about E/M bundling; separate E/M billing rules (like -25) are handled separately.

Copy/paste templates (fast)

Procedure attestation (generic)

  • “Resident performed portions of the procedure under my direction. I was present for the key/critical portions and immediately available for the remainder. Findings: ____. Complications: ____.”

E/M attestation (generic)

  • “I personally evaluated the patient and reviewed the resident’s note. I participated in MDM and management. Key findings: ____. Plan: ____.”

Time-based service attestation (generic)

  • “Total teaching physician time: ___ minutes (exclusive of resident-only time and teaching time). I was present for the time billed.”

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