GX Modifier – Definition and When to Use

What is a Modifier?

A coding modifier is often used when billing health insurance companies. It provides additional information about the procedure code being used, without altering the definition of the code. 

If billing on a CMS1500 form, modifiers go in box 24D, to the right of  the CPT code. There is space available for up to four modifiers.

GX Modifier Definition

The GX modifier is defined as, “item or service expected to be denied as not reasonable and necessary.”

When to Use the GX Modifier

If a Medicare patient is receiving a service that is not a Medicare benefit or has never been covered by Medicare because they deem it statutorily excluded, having the patient fill out an Advance Beneficiary Notice (ABN), is not required. However, if a voluntary ABN was issued, the GX modifier can be used.

This modifier can be combined with the GY modifier.

ABN forms can be obtained via the Center for Medicare & Medicaid Services (CMS) website.

Other ABN Claim Reporting Modifiers


CPT 2021 Professional Edition

What are medical coding modifiers

Medicare Advance Written Notices of Non-Coverage

Memorandum Report: Medicare Payments for Part B Claim with G Modifiers

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