What to Append to Medicare Claims With a Signed ABN?

When a service provided to a Medicare beneficiary may not be covered, healthcare providers often use an Advance Beneficiary Notice of Noncoverage (ABN). This document informs the patient that Medicare might not pay for the service and that they could be held financially responsible. To communicate the presence of an ABN and the coverage determination to Medicare, specific codes, known as modifiers, must be appended to the Current Procedural Terminology (CPT) or Healthcare Common Procedure Coding System (HCPCS) codes on the claim.

Medicare Modifiers for Non-Covered Services

In medical billing, a modifier is a two-character code that provides additional information about a service. For services Medicare may not cover, specific HCPCS modifiers indicate the status of an Advance Beneficiary Notice of Noncoverage (ABN) and the service’s coverage status.

These modifiers include:
GA modifier: “Waiver of Liability Statement Issued, as Required by Payer Policy.” Used when a mandatory ABN is on file for a service Medicare typically covers but expects to deny.
GX modifier: “Notice of Exclusions from Medicare Benefits Statement.” Used when a voluntary ABN is issued for services statutorily excluded from Medicare coverage.
GY modifier: “Item or Service Statutorily Excluded, or Does Not Meet the Definition of Medicare Benefit.” Applies to services statutorily excluded from Medicare coverage for which an ABN was not required or signed.
GZ modifier: “Item or Service Expected to Be Denied as Not Reasonable and Necessary.” Used when a service Medicare typically covers is expected to be denied, but an ABN was not obtained. In such cases, the provider accepts financial liability.

Selecting the Appropriate Modifier

Choosing the correct modifier depends on whether an Advance Beneficiary Notice of Noncoverage (ABN) was signed and if the service is generally covered by Medicare or statutorily excluded.

GA Modifier

The GA modifier applies when a service is usually covered by Medicare but is expected to be denied, such as for medical necessity, and a valid ABN has been signed. For example, if a patient receives more physical therapy sessions than Medicare typically allows and signs an ABN, the GA modifier is used. This signals to Medicare that the patient is aware and has agreed to be financially responsible if the claim is denied.

GX Modifier

The GX modifier is used for services never covered by Medicare because they are statutorily excluded, but the provider has voluntarily issued an ABN. An instance is a routine dental cleaning, which Medicare does not cover, where a provider chooses to have the patient sign a voluntary ABN. Using GX communicates that the patient was informed of their financial liability. This modifier can be paired with GY in certain situations, but not with GA or GZ.

GY Modifier

The GY modifier is appropriate for services statutorily excluded from Medicare coverage when no ABN was required or obtained. For example, if a patient requests new eyeglasses, which are not a Medicare benefit, the GY modifier would be appended to the claim. This informs Medicare the service is not a covered benefit.

GZ Modifier

The GZ modifier is used when a service Medicare typically covers is expected to be denied as not reasonable and necessary, but an ABN was not obtained. In this scenario, the provider accepts the financial risk. For instance, if a provider performs a diagnostic test that may not meet Medicare’s medical necessity criteria, and an ABN was not signed, the GZ modifier would be applied. This ensures Medicare denies the claim, and the provider cannot bill the patient.

Claim Submission with Modifiers

Once the appropriate modifier is selected, append it to the relevant CPT or HCPCS code on the Medicare claim form. For paper claims (CMS-1500 form), modifiers are entered in Box 24D. When submitting claims electronically, the modifier is placed in the designated field associated with the procedure code within the electronic data interchange (EDI) system.

A claim with a GA modifier will generally be denied by Medicare, and the patient will be held responsible for the charges, as outlined in the signed ABN. Conversely, a claim with a GZ modifier will also be denied, but the provider will absorb the cost, as no ABN was obtained.

After submission, healthcare providers must retain the signed Advance Beneficiary Notice of Noncoverage (ABN) in the patient’s record. This document proves the beneficiary was informed of potential non-coverage, protecting the provider during audits or inquiries.