HCPCS Level II modifier
Modifier Q0
Modifier Q0 is a HCPCS Level II modifier. CMS describes it as: Investigational clinical service provided in a clinical research study that is in an approved clinical research study.
Source: CMS HCPCS Level II, October 2026 file dated September 23, 2026. Publisher page
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- Modifier
- Q0
- Type
- HCPCS Level II modifier, maintained by CMS
- CMS description
- Investigational clinical service provided in a clinical research study that is in an approved clinical research study
- 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
- Q1Routine clinical service provided in a clinical research study that is in an approved clinical research study
- PTColorectal cancer screening test; converted to diagnostic test or other procedure
- Q2Demonstration procedure/service
- PSPositron emission tomography (PET) or PET/computed tomography (CT) to inform the subsequent treatment strategy of cancerous tumors when the beneficiary's treating physician determines that the PET study is needed to inform subsequent anti-tumor strategy
- Q3Live kidney donor surgery and related services
- POExcepted service provided at an off-campus, outpatient, provider-based department of a hospital
- Q4Service for ordering/referring physician qualifies as a service exemption
- PNNon-excepted service provided at an off-campus, outpatient, provider-based department of a hospital
Related pages
Questions
What does modifier Q0 mean?
Modifier Q0 is a HCPCS Level II modifier. CMS describes it as: Investigational clinical service provided in a clinical research study that is in an approved clinical research study.
Is modifier Q0 a CPT or a HCPCS modifier?
Q0 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 Q0 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.