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Modifier GX: Notice of liability issued, voluntary under payer policy

Modifier GX is a HCPCS Level II modifier that CMS describes as "Notice of liability issued, voluntary under payer policy", in effect since April 1, 2010. 44 current Medicare billing and coding articles list it.

Compiled from CMS files by the QuickIntell RCM Editorial Team · Data effective · Method: reference methodology · Report a data correction

Data currency: HCPCS Level II file: October 2026 (effective October 1, 2026); Medicare Coverage Database billing and coding articles: MCD release October 8, 2026 (effective October 4, 2026); DMEPOS fee schedule: DME26-D (October 2026) (effective October 1, 2026). Next CMS release: January 1, 2027 (quarterly update) for the HCPCS Level II file and DMEPOS fee schedule; weekly, every Thursday for the Medicare Coverage Database billing and coding articles.

Modifier
GX
Code set
HCPCS Level II
CMS October 2026 HCPCS file
In effect since
April 1, 2010
Group
Liability notices (ABN) and statutory exclusions
Medicare coverage articles
44
current MCD billing and coding articles that list it
DMEPOS fee schedule rows
None
DME26-D

CMS descriptor for modifier GX

Notice of liability issued, voluntary under payer policy

CMS HCPCS Level II file, October 2026 (short descriptor: Voluntary liability notice)

When modifier GX is used

GX shows that a voluntary notice of liability was issued, typically a voluntary ABN for a service Medicare never covers (a statutory exclusion). It can be reported alone or with GY; it is not a substitute for GA when the ABN was required because the service may be denied as not reasonable and necessary.

Basis: Pub. 100-04, chapter 30 (ABN). Summary in our own words; check the payer's current policy before billing.

Medicare coverage articles that list modifier GX

44 current billing and coding articles in the Medicare Coverage Database name modifier GX. Each one sets the contractor's rule for when the modifier is required or accepted.

Denials when modifier GX is wrong or missing

A modifier that does not fit the procedure code comes back with claim adjustment reason code 4 (the procedure code is inconsistent with the modifier used, or a required modifier is missing). When a coverage article requires the modifier and it is absent, the line is usually returned as unprocessable with reason code 16 and a remark code naming the missing information, which is fixed with a corrected claim rather than an appeal. The denial code lookup explains each code.

For teams evaluating QuickIntell software

Where QuickIntell fits with modifiers

QuickCode supports qualified coder review, documentation clarification and the billing handoff, where each modifier is matched to what the record supports. QuickRCM carries claim readiness and the modifier-related denials with configurable automation and human review.

See QuickCode for modifier reviewSee QuickRCM for modifier denials
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Optional software evaluation, not payer support or help with an individual claim. For coverage or payment decisions, use the official sources on this page. Do not include patient information in a demo booking or inquiry.

Frequently asked questions

What does modifier GX mean?

CMS describes modifier GX as "Notice of liability issued, voluntary under payer policy" in the HCPCS Level II file. GX shows that a voluntary notice of liability was issued, typically a voluntary ABN for a service Medicare never covers (a statutory exclusion).

Is modifier GX still valid?

Yes. Modifier GX is active in the CMS October 2026 HCPCS file; CMS added it on April 1, 2010. Payers can still decline to accept it, so check the payer's modifier policy.

Do Medicare coverage articles require modifier GX?

44 current billing and coding articles in the Medicare Coverage Database name modifier GX. Where an article covers the service, it sets the contractor's rule for when the modifier must be reported.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-10. Verify against the primary file before billing or contracting decisions. The reference methodology explains how each figure is computed from these files.

Disclaimer

The descriptor is reproduced from the CMS HCPCS file; the note on when the modifier is used is our own summary of the Medicare rule. Medicaid and commercial plans publish their own modifier policies. Not legal, clinical or billing advice.

Found a figure that does not match the CMS file? Report a data correction with the CMS file and the value you expected; the request reaches the editorial team through the contact form.