Modifier GX is a Medicare HCPCS Level II modifier used to indicate that the supplier issued a voluntary Notice of Liability (NOL) to the beneficiary before providing an item or service that Medicare does not cover. Unlike Modifier GA, which is associated with a required Advance Beneficiary Notice (ABN) for items expected to be denied as not reasonable and necessary, Modifier GX applies when the notice is voluntary because Medicare does not require an ABN for the item or service.
In Durable Medical Equipment (DME) billing, Modifier GX is commonly used for statutorily excluded items or services or items that do not meet the definition of a Medicare benefit, when the supplier chooses to notify the beneficiary of potential financial responsibility.
Correct use of Modifier GX helps document that the beneficiary received advance notice even though Medicare did not require one.
Modifier
GX
Modifier Name
Notice of Liability Issued, Voluntary Under Payer Policy
Plain English Explanation
Modifier GX tells Medicare:
“The supplier voluntarily provided the beneficiary with a written notice explaining that Medicare is not expected to pay for the item or service, even though Medicare did not require this notice.”
It documents transparency with the beneficiary regarding potential financial responsibility.
Purpose of Modifier GX
Modifier GX is used to:
- Indicate that a voluntary notice of liability was issued.
- Document that the beneficiary was informed before receiving a non-covered item or service.
- Support compliant Medicare claim submission.
- Help establish that the beneficiary was notified of possible financial responsibility.
- Differentiate voluntary notices from required ABNs.
Understanding Modifier GX
Modifier GX differs from GA because the notice is voluntary, not required by Medicare.
Medicare generally does not require an ABN for:
- Statutorily excluded services.
- Services that do not meet the definition of a Medicare benefit.
- Certain non-covered DME items.
However, suppliers may still choose to issue a voluntary notice, and Modifier GX identifies that action.
When to Use Modifier GX
Use Modifier GX when:
- The item or service is statutorily excluded from Medicare coverage or is not a Medicare benefit.
- Medicare does not require an ABN.
- The supplier voluntarily provides a notice of liability before furnishing the item or service.
- The claim is submitted to Medicare with the appropriate modifiers.
Common DME examples include:
- Convenience or comfort items excluded from Medicare coverage.
- Equipment that does not meet Medicare’s definition of DME.
- Items specifically excluded by statute.
- Certain upgraded or optional accessories that are not covered.
When NOT to Use Modifier GX
Do not use Modifier GX when:
- A required ABN should be issued (use GA when appropriate).
- No voluntary notice was provided.
- The item is expected to be denied as not reasonable and necessary with a required ABN.
- The item is covered and all Medicare requirements are met.
- The modifier does not accurately describe the billing situation.
Medicare Rules
Under Medicare:
- Modifier GX indicates that a voluntary notice of liability was issued.
- It is commonly reported together with Modifier GY when billing statutorily excluded services or items that are not Medicare benefits.
- Medicare does not require an ABN for these items, but suppliers may voluntarily notify beneficiaries.
- The voluntary notice should be retained in the supplier’s records.
Commercial Insurance Rules
Commercial insurers generally do not use Modifier GX in the same way Medicare does.
Some commercial payers:
- Ignore the modifier.
- Require their own financial responsibility forms.
- Use payer-specific waiver procedures.
Always verify payer-specific policies before billing.
Documentation Requirements
Documentation should include:
- Voluntary Notice of Liability.
- Date the notice was signed (if applicable).
- Beneficiary acknowledgment.
- Physician order, when required.
- HCPCS code.
- Modifier GX.
- Modifier GY, when appropriate.
- Supplier records.
- Proof of delivery, if applicable.
Real Billing Examples
Example 1 – Statutorily Excluded Item
A beneficiary requests an item that Medicare specifically excludes from coverage. The supplier voluntarily issues a notice explaining that Medicare is not expected to pay.
Billing
- Appropriate HCPCS code
- Modifiers GX GY
Example 2 – Non-Covered Comfort Item
A beneficiary requests a comfort accessory that is not covered by Medicare.
The supplier voluntarily provides written notice before dispensing the item.
Billing
- Appropriate HCPCS code
- Modifiers GX GY
Example 3 – Non-DME Item
A supplier furnishes an item that does not meet Medicare’s definition of durable medical equipment.
Billing
- Appropriate HCPCS code
- Modifiers GX GY
Example 4 – Optional Upgrade
A beneficiary elects to receive an optional feature that Medicare does not cover. The supplier voluntarily explains that Medicare is not expected to reimburse the upgrade.
Billing
- Appropriate HCPCS code
- Modifier GX (and other applicable modifiers based on the billing scenario)
Example 5 – Incorrect Use
A supplier bills:
- HCPCS code
- Modifier GX
However, no voluntary notice was provided to the beneficiary.
This is incorrect because Modifier GX may be used only when a voluntary notice of liability has actually been issued.
CMS-1500 Claim Example
| Field | Example |
|---|---|
| HCPCS | Appropriate HCPCS Code |
| Modifier 1 | GX |
| Modifier 2 | GY (when applicable) |
| Diagnosis Pointer | Appropriate ICD-10-CM diagnosis |
| Units | 1 |
Common Denial Reasons
- Modifier GX used without issuing a voluntary notice.
- Incorrect use of GX instead of GA.
- Missing GY modifier when required.
- Incorrect HCPCS code.
- Documentation not retained.
- Invalid modifier combination.
How to Correct the Denial
- Verify whether a voluntary notice was issued.
- Confirm the item is statutorily excluded or not a Medicare benefit.
- Review modifier selection.
- Add Modifier GY if appropriate.
- Submit supporting documentation if requested.
- Resubmit the corrected claim or file an appeal.
Coding Tips
- Use GX only when a voluntary notice has been issued.
- Do not confuse GX with GA.
- Review Medicare coverage before selecting the modifier.
- Keep copies of all voluntary notices.
- When applicable, report GX together with GY.
Modifier GX vs Modifier GA
| Modifier | Description |
| GX | Voluntary notice of liability issued |
| GA | Required ABN issued |
Modifier GX vs Modifier GY
| Modifier | Description |
| GX | Voluntary notice issued |
| GY | Item is statutorily excluded or not a Medicare benefit |
Important: GX and GY are commonly billed together for Medicare non-covered items.
Modifier GX vs Modifier GZ
| Modifier | Description |
| GX | Voluntary notice issued |
| GZ | No ABN obtained for an item expected to be denied as not reasonable and necessary |
Frequently Asked Questions (FAQs)
Q1. What does Modifier GX mean?
Answer: It indicates that the supplier voluntarily issued a Notice of Liability before furnishing an item or service that Medicare is not expected to cover.
Q2. Is Modifier GX the same as GA?
Answer: No. GA is used when a required ABN has been issued. GX is used when the notice is voluntary because Medicare does not require an ABN.
Q3. Is GX commonly billed with GY?
Answer: Yes. GX and GY are frequently reported together for statutorily excluded items or services that are not Medicare benefits.
Q4. Does Modifier GX guarantee payment?
Answer: No. It simply documents that the beneficiary received a voluntary notice of liability.
Q5. Is Modifier GX used only for Medicare?
Answer: It is primarily intended for Medicare billing. Commercial payer use varies.
AR Caller Tips
When following up on claims billed with Modifier GX:
- Verify whether the item is statutorily excluded.
- Confirm that a voluntary notice was provided.
- Check whether Modifier GY should also be reported.
- Review Medicare denial reason codes.
- Document payer guidance and reference numbers.
- Maintain copies of the voluntary notice for audit purposes.
Interview Questions
Question 1
What does Modifier GX represent?
Answer: A voluntary Notice of Liability was issued before furnishing the item or service.
Question 2
What is the difference between GA and GX?
Answer: GA indicates a required ABN was issued, while GX indicates a voluntary notice was issued for an item or service that does not require an ABN.
Question 3
Which modifier is commonly billed with GX?
Answer: Modifier GY.
Question 4
Does Modifier GX mean Medicare will pay the claim?
Answer: No. It simply documents that the beneficiary received advance notice of potential financial responsibility.
Practice Scenario
Scenario
A Medicare beneficiary requests a comfort item that is excluded from Medicare coverage. The supplier voluntarily provides a written notice explaining that Medicare is not expected to pay before dispensing the item.
Question
Which modifiers should be reported?
Answer
Report the appropriate HCPCS code with Modifiers GX and GY, indicating that the supplier voluntarily issued a notice of liability for a statutorily excluded item.
Related DME Modifiers
- GA – Waiver of Liability Statement Issued as Required by Payer Policy
- GY – Item or Service Statutorily Excluded or Does Not Meet the Definition of a Medicare Benefit
- GZ – Item or Service Expected to Be Denied as Not Reasonable and Necessary; No ABN Obtained
- KX – Requirements Specified in the Medical Policy Have Been Met
- RR – Rental Durable Medical Equipment
- NU – New Durable Medical Equipment Purchase
- UE – Used Durable Medical Equipment Purchase
Common Billing Mistakes
- Using GX without issuing a voluntary notice.
- Using GX instead of GA for a required ABN.
- Omitting GY when billing statutorily excluded items.
- Confusing voluntary notices with required ABNs.
- Incomplete documentation.
- Incorrect modifier sequencing.
Key Takeaways
- Modifier GX indicates that a voluntary Notice of Liability was issued before providing a non-covered item or service.
- It differs from Modifier GA, which is used with a required ABN.
- GX is commonly reported with Modifier GY for Medicare-excluded items.
- The supplier should retain documentation of the voluntary notice.
- Proper use of Modifier GX supports compliant Medicare billing and clear beneficiary communication.
References
- CMS Medicare Claims Processing Manual, Chapter 30 – Financial Liability Protections.
- CMS Advance Beneficiary Notice (ABN) and Notice of Liability guidance.
- Medicare Benefit Policy Manual.
- HCPCS Level II Code Book.
- DME Medicare Administrative Contractor (DME MAC) Supplier Manuals.
Conclusion
Modifier GX is an important Medicare modifier that documents a voluntary Notice of Liability for items or services that Medicare does not cover and for which an ABN is not required. It promotes transparency by informing beneficiaries of potential financial responsibility before the item is furnished. When used correctly—often in combination with Modifier GY—it helps ensure compliant billing, proper documentation, and effective communication with beneficiaries.
Educational Disclaimer
This article was prepared with the assistance of artificial intelligence (AI) for educational and informational purposes. It is based on publicly available CMS guidance, Medicare financial liability rules, DMEPOS billing principles, and general medical coding practices. It is not an official publication of CMS or the American Medical Association (AMA). Always consult the latest CMS Medicare Claims Processing Manual, the HCPCS Level II Code Book, DME Medicare Administrative Contractor (DME MAC) guidance, and payer-specific billing policies before coding, billing, or submitting claims.