The GA Modifier and the ABN: How DME Suppliers Bill When Medicare May Deny

2026-10-06 · Caduvo Team

Learn when DME suppliers must append the GA modifier, how it differs from GZ and GY, and how to execute Form CMS-R-131 compliantly to shift payment liability.

When a durable medical equipment (DME) supplier furnishes equipment that Fee-for-Service (FFS) Medicare is expected to deny as not medically reasonable and necessary, billing without liability protection creates an unrecoverable loss. Submitting a claim that is denied under medical necessity rules forces the supplier to absorb the financial burden unless the patient received written notification before receiving the item. Appending the ga modifier tells Medicare Administrative Contractors (MACs) that the supplier holds an executed Advance Beneficiary Notice of Non-coverage (Form CMS-R-131), transferring payment liability to the beneficiary upon denial.

Getting this mechanism right protects operating cash flow on contested claims. Getting it wrong exposes suppliers to claim reversals, audit findings, and non-compliance liabilities under Medicare rules.

When to Append the GA Modifier: Statutory Grounds and Trigger Events

The ga modifier stands for "Waiver of Liability Statement Issued as Required by Payer Policy." Under CMS billing and coding guidance, modifier GA applies only when services will be denied under reasonable and necessary provisions: sections 1862(a)(1), 1862(a)(9), 1879(e), or 1879(g) of the Social Security Act. Suppliers append modifier GA when they anticipate that Medicare will deny a specific item or service as not reasonable and necessary and they have an executed Form CMS-R-131 signed by the beneficiary on file.

According to the CMS ABN tutorial, health care providers and suppliers must issue an ABN to transfer financial liability to the patient when they expect Medicare to deny coverage for an item or service it generally covers. An ABN must be issued when an item, test, service, or care is not reasonable and necessary under Medicare Program standards, including when the item:

Is not indicated for the diagnosis or treatment of illness or injury or to improve the functioning of a malformed body member
Is experimental and investigational or considered research only
Exceeds the number of services allowed in a specific period for that diagnosis
Fails to meet medical necessity under an active local coverage determination (LCD)

For DMEPOS suppliers specifically, the CMS ABN tutorial instructs that an ABN must also be issued before providing an item or service Medicare will not cover because:

The provider accepted prohibited unsolicited phone contacts
The supplier has not met supplier number requirements
A noncontract supplier provides an item listed in a competitive bidding area
The patient wants the item or service before the advance coverage determination is completed

Under Noridian billing instructions, correct use requires appending modifier GA when an ABN has been provided to the patient and denial is expected because the item is not reasonable and necessary or fails an active LCD. Noridian lists incorrect use as appending modifier GA on a routine basis for all services performed by a provider, or appending it when the provider has no expectation that an item or service will be denied.

The Liability Matrix: Distinguishing GA from GZ and GY

Medicare uses specific two-letter HCPCS modifiers to report expected non-coverage and determine whether financial liability rests with the beneficiary or the billing supplier.

Modifier GA (Signed ABN on File)

As outlined in First Coast Service Options billing guidance, modifier GA must be used when physicians, practitioners, or suppliers want to indicate that they expect Medicare will deny a service as not reasonable and necessary, and they do have an ABN signed by the beneficiary on file. Effective April 1, 2010, Part A MAC systems automatically deny services billed with modifier GA, as noted in CMS billing guidance. Under Noridian appeal rules, line items submitted with modifier GA deny as beneficiary-liable. Both the beneficiary and the provider retain appeal rights. If a provider needs to add modifier GA to a processed claim, they cannot do so through a clerical reopening; they must submit an appeal that includes a copy of the valid ABN.

Modifier GZ (Expected Denial, No ABN)

Modifier GZ is mandatory when a supplier expects Medicare to deny an item as not reasonable and necessary but does not have a signed ABN on file. According to First Coast billing guidance and Palmetto GBA instructions, effective July 1, 2011, all claim line items submitted with a GZ modifier are denied automatically and are not subject to complex medical review. The line item denies as provider-liable. Under Noridian appeal rules, providers may request to add or remove modifier GZ through clerical reopenings without submitting documentation, but an unpaid line billed under GZ remains the supplier's financial responsibility.

Modifier GY (Statutorily Excluded Items)

Modifier GY indicates that an item or service is statutorily non-covered. Under Noridian appeal rules, line items billed with modifier GY deny as beneficiary-liable, and both the beneficiary and provider retain appeal rights. A provider may request to remove modifier GY via reopening, but may not request to add it via reopening.

Worked DME Example: Delivering CPAP Code E0601 Ahead of Coverage Rules

Understanding how modifier GA operates in routine dme billing requires tracking an order through intake, notice execution, and adjudication.

Clinical and Administrative Intake

A supplier receives a physician order to dispense a continuous positive airway pressure (CPAP) device, reported under HCPCS code E0601. Reviewing the patient file against the DME MAC Local Coverage Determination shows that the ordering documentation does not fulfill LCD clinical criteria. In another common scenario, the beneficiary wants the item delivered immediately before an advance coverage determination has been completed by the MAC.

Because the item does not meet medical necessity criteria under the LCD, or is being delivered before the coverage determination is complete, the supplier expects Medicare will deny the claim. According to Palmetto GBA and FCSO, all claims not meeting the medical necessity of an LCD must append modifier GA or modifier GZ.

Issuing Form CMS-R-131

Before transferring possession of the equipment to the patient, the supplier issues Form CMS-R-131:

Item Identification: Continuous positive airway pressure device, HCPCS code E0601.
Reason Medicare May Deny: The supplier identifies why Medicare is expected to deny the service under Medicare Program standards, such as failure to satisfy active LCD criteria or delivery taking place before an advance coverage determination is completed.
Beneficiary Signature: As specified in CMS billing guidance, Form CMS-R-131 is signed by the beneficiary to indicate that he or she accepts responsibility for payment.

Claim Formatting and Adjudication

The billing department submits the claim line with the following coding:

HCPCS Code: E0601
Modifier: GA

When the MAC processes the claim, it evaluates the line item against coverage policies. Because documentation does not satisfy LCD guidelines, the MAC denies coverage. Because modifier GA was appended, the claim denies as beneficiary-liable. The supplier may collect payment from the patient. In addition, both the beneficiary and the supplier retain appeal rights under Noridian instructions.

If the supplier had delivered the CPAP device without obtaining a signed Form CMS-R-131, the supplier would be required to append modifier GZ. The claim would automatically deny as provider-liable under FCSO and Palmetto GBA rules, and the supplier could not bill the beneficiary.

Compliant Execution of Form CMS-R-131

According to CMS Program Memorandum AB-02-168, use of the GA modifier is permissible only in conjunction with Form CMS-R-131 for items or services furnished on or after January 1, 2003. Carriers and MACs do not routinely require the physical submission of an ABN when a claim includes modifier GA, but the signed form must remain on file.

To ensure Form CMS-R-131 transfers liability successfully, suppliers must comply with operational rules documented by CMS:

Avoid routine or blanket distribution: According to Noridian guidelines, appending modifier GA on a routine basis for all services performed by a provider, or appending it without expectation of denial, is incorrect. Suppliers must evaluate claims individually.
Identify specific statutory or policy grounds: Under the CMS ABN tutorial, suppliers must issue the notice when care is not reasonable and necessary under program standards—such as when an item is not indicated for the diagnosis or treatment of illness or injury, exceeds frequency limits, or is furnished before an advance coverage determination.
Issue the notice prior to furnishing items: Under CMS MLN006266, an advance written notice must be issued before providing the item or service. Delivering an ABN after the beneficiary receives the equipment leaves financial liability with the supplier.
Document witnessed refusals: Under CMS guidelines, modifier GA may be used on assigned claims when a patient refuses to sign the ABN, provided the refusal is properly witnessed.

MedTech reimbursement teams can reference Caduvo to evaluate active Medicare coverage determinations and policy parameters before dispatching devices.

Actionable Steps for DME Revenue Cycle Teams

Managing non-covered equipment orders requires structured workflows across intake, delivery, and billing:

Audit intake documentation against LCD criteria: Before scheduling delivery, determine whether the patient's records meet coverage policy. If requirements are missing or the patient demands delivery before an advance coverage determination, issue Form CMS-R-131.
Confirm Form CMS-R-131 details before appending modifier GA: Verify that the notice identifies the equipment (such as E0601), documents the reason Medicare may deny payment under program standards, and contains a beneficiary signature obtained prior to furnishing the item.
Submit modifier GZ when an ABN was missed: If an item fails medical necessity rules and no signed ABN exists, append modifier GZ. Never append modifier GA without an executed notice on file.
Archive signed forms for audits: Although MACs do not routinely require ABN submission with initial claims under CMS Program Memorandum AB-02-168, maintain the signed notice in the patient file for post-payment review.
Use formal appeals to add omitted GA modifiers: If a valid ABN was obtained but modifier GA was accidentally left off the claim, file an appeal accompanied by the signed Form CMS-R-131. Clerical reopenings cannot be used to add modifier GA.

Sources

General information, not regulatory, legal or reimbursement advice. Company and product names belong to their owners; a mention does not imply affiliation or endorsement. Report an error. Data and corrections policy.