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S9991 HCPCS Level II code: Services provided as part of a phase iii clinical trial

S9991 is the HCPCS code for “Services provided as part of a phase iii clinical trial” in CMS’s October 2026 release, in effect from Oct 1, 2026.

Official description

S9991

Services provided as part of a phase iii clinical trial

Short description: Services provided as part of

HCPCS · United States

Notes for S9991

As CMS prints them, with any note S9991 takes from the headings above it.

Note

  • CMS processing note 0088: "S" CODES ARE UNIQUE TEMPORARY CODES ESTABLISHED BY BCBSA AND HIAA FOR PRIVATE PAYOR USE. THEY ARE NOT VALID NOR PAYABLE BY MEDICARE.

Medicare details

The indicators CMS publishes with S9991 in its October 2026 file. They describe Medicare’s handling, not another payer’s.

Medicare coverage
Not payable by Medicare
Medicare pricing
Service not separately priced by Part B (e.g., services not covered, bundled, used by Part A only, etc.)
Type of service
Other medical items or services
BETOS category
Undefined codes
Added
Jan 1, 2000

Where S9991 sits

  1. 1S codesTemporary national codes (non-Medicare)
  2. 2Active code S9991Services provided as part of a phase iii clinical trial

Source and release

Data release
HCPCS Level II · October 2026
Effective date
Oct 1, 2026
Publisher
CMS

This page is built from the HCPCS Level II catalog that Vero Codes reads when it suggests codes: Centers for Medicare & Medicaid Services’s October 2026 release, imported from the publisher’s file and checked against it. The description, notes and structured data come from the same record.

See S9991 in the CMS source

Frequently asked questions

What does HCPCS code S9991 mean?

S9991 is the HCPCS code for “Services provided as part of a phase iii clinical trial” in CMS’s HCPCS Level II October 2026 release.

Does Medicare cover S9991?

CMS lists S9991’s Medicare coverage as “Not payable by Medicare” and its pricing as “Service not separately priced by Part B (e.g., services not covered, bundled, used by Part A only, etc.)”. Coverage and payment still depend on the patient, the setting, the documentation and the payer.

Which HCPCS Level II release does this page use?

It uses CMS’s October 2026 release, in effect from Oct 1, 2026 to Dec 31, 2026. It is a reference: confirm the code against the current list and the payer’s rules before you submit it.

Codes beside S9991

S9981Medical records copying fee, administrativeS9982Medical records copying fee, per pageS9986Not medically necessary service (patient is aware that service not medically necessary)S9988Services provided as part of a phase i clinical trialS9989Services 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 trialS9992Transportation costs to and from trial location and local transportation costs (e.g., fares for taxicab or bus) for clinical trial participant and one caregiver/companionS9994Lodging costs (e.g., hotel charges) for clinical trial participant and one caregiver/companionS9996Meals for clinical trial participant and one caregiver/companionS9999Sales tax