HCPCS Level II modifier
Modifier GK
Modifier GK is a HCPCS Level II modifier. CMS describes it as: Reasonable and necessary item/service associated with a ga or gz modifier.
Source: CMS HCPCS Level II, October 2026 file dated September 23, 2026. Publisher page
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- Modifier
- GK
- Type
- HCPCS Level II modifier, maintained by CMS
- CMS description
- Reasonable and necessary item/service associated with a ga or gz modifier
- Claim form
- CMS-1500 item 24D, up to four modifiers per line. 837P SV101-3 to SV101-6.
- Guidance
- CMS HCPCS quarterly update
Related modifiers
- GLMedically unnecessary upgrade provided instead of non-upgraded item, no charge, no advance beneficiary notice (ABN)
- GJ"opt out" physician or practitioner emergency or urgent service
- GMMultiple patients on one ambulance trip
- GHDiagnostic mammogram converted from screening mammogram on same day
- GNServices delivered under an outpatient speech language pathology plan of care
- GGPerformance and payment of a screening mammogram and diagnostic mammogram on the same patient, same day
- GOServices delivered under an outpatient occupational therapy plan of care
- GFNon-physician (e.g. nurse practitioner (NP), certified registered nurse anesthetist (CRNA), certified registered nurse (CRN), clinical nurse specialist (CNS), physician assistant (PA)) services in a critical access hospital
Related pages
Questions
What does modifier GK mean?
Modifier GK is a HCPCS Level II modifier. CMS describes it as: Reasonable and necessary item/service associated with a ga or gz modifier.
Is modifier GK a CPT or a HCPCS modifier?
GK is a HCPCS Level II modifier from the CMS quarterly HCPCS file. Two-digit numeric modifiers, such as 25 or 59, are CPT modifiers.
Where does modifier GK go on a claim?
On the CMS-1500 it goes in item 24D next to the procedure code. Each line holds up to four modifiers. On an 837P it goes in SV101-3 to SV101-6.
What denial comes back when a modifier is wrong?
A missing or mismatched modifier often comes back as CARC 4. A modifier that was not valid on the date of service comes back as CARC 182. A bundling edit the modifier should have bypassed comes back as CARC 97 or 236.