ABN with GA and GY Modifiers And Their Correct Use

Many billing professionals struggle with one persistent question: when do I use an ABN with a GA modifier, and when do I use a GY modifier instead?

This comprehensive guide breaks down everything you need to know about ABNs, GA modifiers, and GY modifiers, including when to use each one, how they differ, and practical scenarios to help you apply this knowledge in your daily billing operations.

Understanding the Basics: What Is an ABN?

An Advance Beneficiary Notice (ABN), formally known as Form CMS-R-131, is a vital document issued to Medicare beneficiaries before services are rendered. Its primary purpose is to inform patients that Medicare may not cover a particular service and that they could be financially responsible for the cost.

The ABN serves three essential functions in medical billing:

Patient Protection:

It ensures beneficiaries understand potential out-of-pocket costs before receiving services, allowing them to make informed decisions about whether to proceed.

Provider Protection:

A properly executed ABN shifts financial liability from the provider to the patient if Medicare denies the claim, protecting practices from having to write off unpaid services.

Regulatory Compliance:

Medicare requires ABNs in specific situations, and failure to issue them when necessary can result in compliance issues and lost revenue.

The ABN must be issued before the service is provided, giving patients adequate time to consider their options. Patients can choose to receive the service and accept financial responsibility, decline the service entirely, or proceed with the understanding that they’ll appeal if Medicare denies coverage.

The GA Modifier: When Medical Necessity Is Uncertain

The GA modifier plays a crucial role when you anticipate a Medicare denial based on medical necessity, but you’ve taken the proper steps to inform your patient through an ABN.

In 2011, Medicare paid nearly $744 million for Part B claims with G modifiers that providers expected to be denied as not reasonable and necessary or as not being covered by Medicare.

When to Use the GA Modifier

Apply the GA modifier in situations where you reasonably expect Medicare to deny a claim because the service doesn’t meet medical necessity criteria according to Local Coverage Determinations (LCDs) or National Coverage Determinations (NCDs). Common scenarios include:

• Diagnostic tests are ordered more frequently than Medicare guidelines allow
• Procedures that don’t align with approved indications in coverage policies
• Services that may be considered not reasonable and necessary for the patient’s specific diagnosis
• Screening tests performed outside Medicare’s approved timeframes

What Is the Application Process

Issue the ABN: 

Present Form CMS-R-131 to the patient before providing the service, clearly explaining why Medicare might not cover it and the estimated cost they may owe.

Obtain Patient Response: 

Have the patient sign the ABN and select one of three options: agree to pay if Medicare denies, decline the service, or receive the service but appeal if denied. If the patient refuses to sign, document this refusal on the form.

Append the GA Modifier: 

Add the GA modifier to the appropriate HCPCS or CPT code on the claim form. This signals to Medicare that you have a signed ABN on file.

Maintain Documentation: 

Keep the completed ABN in the patient’s medical record for at least four years. While you don’t routinely submit the ABN with claims, Medicare may request it during audits or appeals.

Billing Outcomes with GA

When Medicare processes a claim with a GA modifier and denies it for lack of medical necessity, the system automatically transfers financial responsibility to the patient. The beneficiary receives a Medicare Summary Notice (MSN) explaining the denial and their obligation to pay. This seamless liability shift is why proper ABN execution with the GA modifier is so valuable for protecting practice revenue.

The GY Modifier: Non-Covered Services

The GA modifier addresses medical necessity concerns, while the GY modifier manages an entirely different category. Such as services that Medicare never covers under any circumstances due to statutory exclusions.

When to Use the GY Modifier

Apply the GY modifier for services explicitly excluded from Medicare benefits by law, regardless of medical necessity. These statutory non-covered services include:

• Routine physical examinations beyond Medicare’s preventive visit definitions
• Cosmetic procedures
• Hearing aids and routine hearing examinations
• Routine foot care for most patients
• Custodial care services
• Self-administered medications
• Services provided outside the United States

The key distinction is that medical necessity isn’t even considered for these services—Medicare excludes them by policy definition.

Why ABNs Aren’t Required with GY

Because Medicare categorically excludes GY-modified services from coverage, the ABN process doesn’t apply. Patient liability is automatic, and the statutory exclusion itself provides notice that Medicare won’t pay. However, good practice dictates that you should still inform patients verbally that the service isn’t covered and provide cost estimates.

Proper Documentation and Billing

When billing with a GY modifier, include a clear explanation in the claim remarks section (Item 19 on the CMS-1500 form or the electronic equivalent). For example: “Service not covered under Medicare statutory exclusion – routine physical examination.”

The claim will generate a denial, which serves multiple purposes: it creates a formal denial notice for the patient, allows secondary insurance (if applicable) to process the claim, and documents that the service was provided at the patient’s request with their understanding of non-coverage.

Applying GA and GY in Real-World Billing

Case Study: Wound Care and Non-Covered Skin Substitute Products

The ABCs of ABNs, Advances in Skin & Wound Care Journal

Wound care presents unique challenges for ABN and modifier usage because Medicare coverage varies significantly by wound type, product selection, and treatment protocols. This case demonstrates proper application of the GY modifier for statutorily non-covered products.

The Clinical Scenario

A wound care specialist treats a Medicare patient with a diabetic foot ulcer (DFU) that has failed to respond to standard wound care for six weeks. The physician determines that a bioengineered skin substitute could accelerate healing and prevent amputation.

The Coverage Challenge: 

Under Medicare Local Coverage Determination (LCD) MP371, certain skin substitute products are listed in Appendix A (covered products) while others appear in Appendix B (non-covered products). Specifically, Q4303 (Complete aa) is non-covered regardless of diagnosis, ulcer severity, or prior care attempts.

The physician believes Q4303 would be clinically optimal for this patient’s specific wound characteristics, but Medicare categorically excludes it from coverage.

Proper Billing Approach

Verify Coverage Status: 

Before selecting a product, the provider checked the Medicare Administrative Contractor’s LCD Appendix A for covered Q-codes. When Q4303 appeared in Appendix B (non-covered), the provider confirmed that it was a statutory exclusion, not a medical necessity question.

Patient Communication: 

Since the non-covered product was clinically appropriate, the provider issued an Advance Beneficiary Notice (ABN) explaining that Medicare categorically excludes Q4303 from coverage. The ABN included:

• A clear statement that Medicare never covers this product under any circumstances
• The estimated cost of $850 for the product and application
• Patient’s three options: accept financial responsibility, use a covered alternative, or decline treatment

Billing with GY Modifier: 

After the patient signed the ABN agreeing to financial responsibility, the provider performed the application and billed CPT codes 15271 (application of skin substitute, first 25 sq cm) and Q4303 (the specific product code). The claim was submitted with the GY modifier appended to make the patient or secondary payer responsible for payment.

Claim Processing: 

Medicare automatically denied the claim with a statutory exclusion code. This formal denial notice served multiple purposes:

• Documented the non-coverage for the patient’s records
• Allowed the patient’s supplemental insurance to review the claim (some Medigap policies cover services Medicare excludes)
• Created a clear audit trail showing proper billing procedures

Why This Approach Was Correct

GY vs. GA Decision: This scenario required GY, not GA, because:

• The exclusion was based on Medicare policy (LCD Appendix B listing), not medical necessity for this specific patient.
• Medicare will not pay for Q4303 even with complete documentation proving medical necessity.
• The coverage determination is categorical, not case-specific.

ABN Still Required: 

Although GY modifiers don’t technically mandate ABNs, issuing one was good practice because:

• The patient needed a clear understanding of the $850 out-of-pocket cost
• Written documentation protected both the provider and the patient
• It demonstrated compliance with patient-centered care principles

The reference article “The ABCs of ABNs” from Advances in Skin & Wound Care (March 2010) provided foundational guidance on ABN usage in wound care settings that remains relevant today.

2026 CMS Updates to Monitor

As we move through 2026, several policy areas may affect ABN and modifier usage:

Medicare continues to refine medical necessity criteria for high-volume diagnostic tests and imaging studies. Stay alert for LCD updates in your region that might shift services from covered to necessity-questionable categories requiring ABNs with GA modifiers.

Payment policy changes for certain preventive services could affect frequency limits and coverage criteria, impacting when ABNs become necessary.

Conclusion

The modifiers GA and GY may seem like small details in medical billing. However, they can mean the difference between getting paid and writing off services. They also affect claim processing speed, which can lead to costly rejections. Plus, they impact regulatory compliance and audit risk.

Knowing that GA modifies medical necessity and provides mandatory ABN protection. GY handles statutory exclusions without requiring an ABN. This provides you with a clear path for your billing decisions.

Get ready to strengthen your billing compliance! Book a free billing audit consultation. Discover ways to improve your ABN and modifier processes. Reach out to our billing experts now and take the next step towards excellence in billing.

FAQS

What is the GA or GY modifier?

The GA HCPCS modifier indicates that an ABN is on file. The GY HCPCS modifier indicates that an item or service is statutorily non-covered or is not a Medicare benefit.

Which modifier is used for ABN?

GA Modifier

When to use the 59 or 51 modifier?

Modifier 51 differs from modifier 59 in that it applies to procedures that may be more commonly expected to be performed during the same session.

What should a patient do after receiving an ABN?

Patient Options After Receiving an ABN

• Accept the Service and Pay: If you believe the service is necessary, you can agree to receive it and be ready to cover the costs if Medicare denies the claim. …
• Decline the Service: You have the option to refuse the service if you don’t want to incur the additional costs.