HCPCS Level II modifier
Modifier AG
Modifier AG is a HCPCS Level II modifier. CMS describes it as: Primary physician.
Source: CMS HCPCS Level II, October 2026 file dated September 23, 2026. Publisher page
Run it in Rivvi
Check the codes on your claims export
Upload a claims export. Rivvi flags ICD-10 and HCPCS codes that are not billable or are replaced. It does not check modifiers.
Check my exportFree to start. Opens Rivvi, the AI workspace for healthcare teams.
- Modifier
- AG
- Type
- HCPCS Level II modifier, maintained by CMS
- CMS description
- Primary physician
- 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
- AHClinical psychologist
- AFSpecialty physician
- AIPrincipal physician of record
- AERegistered dietician
- AJClinical social worker
- ADMedical supervision by a physician: more than four concurrent anesthesia procedures
- AKNon participating physician
- ACInitial onboarding support payment for access beneficiary enrollment, device/app setup, and care coordination activities; first month only; once per beneficiary per track
Related pages
Questions
What does modifier AG mean?
Modifier AG is a HCPCS Level II modifier. CMS describes it as: Primary physician.
Is modifier AG a CPT or a HCPCS modifier?
AG 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 AG 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.