Comparison · Billing

Modifier GA vs GZ vs GY (Medicare ABN modifiers)

GA signals an ABN is on file for a service Medicare may deny. GZ signals no ABN was obtained. GY signals the service is statutorily excluded — never a Medicare benefit.

Last reviewed May 24, 2026

Side by side

Option A

Modifier GA

Waiver of liability statement issued as required by payer policy, individual case. ABN is on file; patient may be billed if Medicare denies.

Modifier GA
  • ABN executed before the service.
  • Permits balance-billing the patient on Medicare denial.
Option B

Modifier GZ / GY

GZ — service is expected to be denied as not reasonable and necessary, and no ABN was obtained (patient cannot be balance-billed). GY — service is statutorily excluded from Medicare; never a covered benefit.

Modifier GZ / GY
  • GZ: Medicare will auto-deny; the practice writes off.
  • GY: Used to generate a denial so a secondary payer will process.
  • Distinct purposes — GZ is a process failure marker, GY is a statutory-exclusion marker.
Patient liability
GAPatient may be billed on denial
GZ / GYGZ: patient may not be billed. GY: patient may be billed (no Medicare benefit ever applied)
ABN executed
GAYes
GZ / GYGZ: no. GY: not required (not a Medicare benefit)
Why used
GACover the practice when Medicare may deny a service that is sometimes covered
GZ / GYGZ: documents that no ABN was obtained. GY: triggers denial to send to a secondary payer
Common scenarios
GAFrequency-limited screenings, non-covered preventive variations
GZ / GYGZ: ABN process failure. GY: routine foot care, hearing aids, cosmetic services

When to use Modifier GA

  • A service Medicare sometimes covers but may deny based on frequency/diagnosis, ABN signed beforehand.

When to use Modifier GZ / GY

  • GZ: the practice failed to get an ABN and Medicare will likely deny — append GZ; do not balance-bill.
  • GY: routine foot care, hearing aids, or other statutorily-excluded services — append GY so the claim denies cleanly for secondary processing.

Common mistakes

  • Using GA without an executed ABN — invalid; switches to GZ.
  • Using GY for a service that is sometimes covered (it is for statutory exclusions only).
  • Balance-billing the patient on a GZ-modified service.

Sources

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Authored by D3rx

D3rx is a healthcare-billing and compliance research aid maintained by D3rx Inc. Articles are drafted by an LLM (Anthropic Claude) against primary HHS, OCR, CMS, eCFR, NIST, and state-regulator publications, and reviewed for restraint and source fidelity by the D3rx team.

Reviewer status: a named credentialed reviewer (CHC, CHPC, or healthcare attorney) is being engaged. Until that engagement is finalized, this page does not claim credentialed review.

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This comparison is a research aid for billing and compliance staff. It does not provide legal, medical, or financial advice and does not replace counsel. References cited link to primary sources at CMS, HHS, OCR, eCFR, NIST, and the relevant payer or state regulator. Last reviewed May 24, 2026.