S9991 — Services provided as part of a phase iii clinical trial
S9991 is a HCPCS Level II code for services provided as part of a phase iii clinical trial. It belongs to the Temporary National Codes (Non-Medicare) section. Medicare does not pay it — see the coverage note below before you bill it.
Medicare coverage: Not payable by Medicare
Medicare does not pay this code. It may still be valid for another payer, but a Medicare claim carrying it will not be reimbursed.
From the coverage field of the CMS Alpha-Numeric HCPCS File, release 2026Q3-Jul. This states Medicare’s position on the code, not on your particular claim.
Physician fee schedule statusI
Not valid for Medicare purposes. Medicare uses another code.
Global period: XXX
Want the dollar amount for your locality? The fee calculator applies your GPCI and the current conversion factor.
The CMS record for S9991
- Long descriptor
- Services provided as part of a phase iii clinical trial
- Short descriptor
- Services provided as part of
- Added
- January 1, 2000
- BETOS
- Z2
- Pricing indicator
- 00 — Not priced by Part B
The official wording. This is what the code means.
CMS's 28-character form, which is what shows up on a remittance advice.
When CMS introduced the code.
Berenson-Eggers Type of Service — CMS's own analytic grouping.
Service not separately priced by Part B — not covered, bundled into another service, or used by Part A only.
Codes adjacent to S9991
HCPCS has no hierarchy — related items simply sit next to each other in the numbering. If S9991 is not quite right, the correct code is very often within a few positions of it.
- S9976Lodging, per diem, not otherwise classified
- S9977Meals, per diem, not otherwise specified
- S9981Medical records copying fee, administrative
- S9982Medical records copying fee, per page
- S9986Not medically necessary service (patient is aware that service not medically necessary)
- S9988Services provided as part of a phase i clinical trial
- S9989Services provided outside of the united states of america (list in addition to code(s) for service(s))
- S9990Services provided as part of a phase ii clinical trial
- S9992Transportation costs to and from trial location and local transportation costs (e.g., fares for taxicab or bus) for clinical trial participant and one caregiver/companion
- S9994Lodging costs (e.g., hotel charges) for clinical trial participant and one caregiver/companion
- S9996Meals for clinical trial participant and one caregiver/companion
- S9999Sales tax
- T1000Private duty / independent nursing service(s) - licensed, up to 15 minutes
- T1001Nursing assessment / evaluation
- T1002Rn services, up to 15 minutes
- T1003Lpn/lvn services, up to 15 minutes
Questions about S9991
What is HCPCS code S9991?
S9991 is a HCPCS Level II code for services provided as part of a phase iii clinical trial. It sits in the Temporary National Codes (Non-Medicare) section.
Does Medicare cover S9991?
The CMS HCPCS file marks S9991 as "Not payable by Medicare". Medicare does not pay this code. It may still be valid for another payer, but a Medicare claim carrying it will not be reimbursed.
How is S9991 paid under the physician fee schedule?
S9991 carries PFS status code I. Not valid for Medicare purposes. Medicare uses another code.