What is Modifier GY (Statutorily Excluded)? Definition, Formula, and Benchmark

Modifier GY (Statutorily Excluded) identifies a service as excluded from Medicare coverage by statute rather than by medical-necessity determination. The distinction matters because statutory exclusions do not require an Advance Beneficiary Notice (ABN); the patient is informed by virtue of the statutory nature of the exclusion that Medicare does not cover such services. Modifier GY tells Medicare to deny the claim and establishes that the patient was always going to be liable.

Examples of statutorily excluded services include cosmetic surgery (except for reconstructive procedures after accident or congenital anomaly), hearing aids and related services, custodial care, services performed by a dentist for non-covered dental conditions, and routine foot care. The statutory exclusion list is defined by Medicare law and is separate from the medical-necessity-based coverage determinations that trigger Modifier GA.

Documentation requirements for Modifier GY are substantially lighter than Modifier GA because no ABN is required. The service itself must be clearly statutorily excluded; appropriate diagnosis coding supports the exclusion status. For example, cosmetic blepharoplasty is statutorily excluded; the diagnosis coding would reflect the cosmetic nature of the service, and Modifier GY identifies it as such. If the same blepharoplasty were medically necessary for visual field impairment, it would not be statutorily excluded and Modifier GY would be inappropriate.

Reimbursement: Medicare denies Modifier GY claims. The patient is directly liable for the service. The provider bills the patient directly per the pre-service financial discussion. Commercial secondary insurance may cover the service if not excluded by the commercial plan; the Medicare denial supports coordination of benefits processing.

For RCM operations, Modifier GY applies in specialty practices performing both covered and non-covered services (plastic surgery, dermatology for cosmetic, ophthalmology for refractive services). Front-desk staff should obtain pre-service financial acknowledgement from patients for statutorily excluded services even though ABN is not required, because patient understanding and payment collection are the primary operational concerns.

Denial and audit patterns for Modifier GY include failure to apply when the service is clearly statutorily excluded (resulting in claim rejection for missing modifier) and inappropriate application when the service may actually be medically necessary (creating audit exposure when the service should have been billed as covered). Practices serving statutorily excluded service lines should have clear coding policies identifying which services trigger Modifier GY and documentation requirements supporting the exclusion classification.

Common confusion with Modifier GY arises when services are partially excluded — for example, certain foot care services are excluded unless the patient has a systemic condition meeting specific criteria. In these hybrid cases, accurate diagnosis coding is the primary determinant; Modifier GY applies only when the excluded pathway is appropriate and the covered-services exception does not apply.