WILLIAM M. GREIF MD
NPI 1013095108
Surgery in Walnut Creek, CA
About William M. Greif Md NPPES
Official registry information on file with the National Plan and Provider Enumeration System.
WILLIAM M. GREIF MD (NPI 1013095108) is an individual surgery provider in Walnut Creek, California, licensed in California (G85813) and active in the NPI registry since November 2006. He is enrolled in Medicare PECOS and is a graduate of Stanford University School Of Medicine (1993).
NPPES Registry Identity
Specialties & Licenses
Other Identifiers 1
Medicare Participation & PECOS CMS
Medicare enrollment, assignment, billing reassignment, and ordering and referring status from CMS.
Medicare Enrollment Status
Enrolled in Medicare and accepts Medicare assignment
William M. Greif Md is registered in PECOS and agrees to accept the Medicare-approved amount as full payment. Medicare patients are not billed beyond the standard deductible and coinsurance.
Medicare Billing Reassignment
Medicare enrollment records show William Greif reassigns Medicare billing to 1 organization. The organization bills Medicare for the services this provider delivers there.
Richmond, CA 94801
- Reassigned Medicare billing, California enrollment
- 20,078 clinicians in this Medicare group
Source: CMS Revalidation Reassignment List, October 2026 release. Reassignment records can lag staffing changes; confirm a current affiliation with the organization.
Physician Visit Costs CMS claims · ZIP area
Typical Medicare office-visit costs in the 94596 ZIP code area, from fee-for-service claims. These are area statistics, not this provider’s prices; actual charges vary by service and coverage.
Other Providers at the Same Location NPPES 20
Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.
WALNUT CREEK, CA 94596
WALNUT CREEK, CA 94596
Frequently Asked Questions NPPES & CMS
Common questions about this NPI record, answered from the official NPPES registry and CMS datasets shown on this page.
What is William Greif's NPI number?
The NPI number for William Greif is 1013095108. It was assigned to this individual provider in the NPPES registry on November 2, 2006.
Where is William Greif located?
William Greif practices at 1425 S Main St, Walnut Creek, CA 94596. The listed phone number is (925) 295-4000.
What is William Greif's specialty?
The primary specialty registered for this NPI is Surgery with taxonomy code 208600000X.
Is William Greif enrolled in Medicare?
Yes. William Greif is registered in the Medicare PECOS system and accepts Medicare assignment, which means accepting the Medicare-approved amount as payment in full for covered services.
Which organization bills Medicare for William Greif's services?
According to the CMS Revalidation Reassignment List (October 2026 release), William Greif reassigns Medicare benefits to Permanente Medical Group Inc (Richmond, CA). The reassignment is filed with Medicare on form CMS-855R, signed by both the clinician and the organization, and lets the organization bill Medicare and receive payment for William Greif's services. Reassignment records can lag staffing changes; confirm current arrangements with the organization.
When was this NPI record last updated?
The NPPES record for William Greif was last updated on December 13, 2021. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 4 years ago. If this record has changed at CMS more recently, you can request an on-demand re-check against the live CMS registry, directly from this page.
# William M. Greif, MD · NPI 1013095108
Surgery physician in Walnut Creek, California. Individual provider, active in the CMS NPPES registry since November 2, 2006.
## Identity
- **NPI:** 1013095108 (Entity type: Individual)
- **Enumerated:** November 2, 2006
- **Primary specialty:** Surgery · taxonomy 208600000X
- **State license:** G85813 (California)
- **Sole proprietor:** No
## Practice location
- **Address:** 1425 S MAIN ST, Walnut Creek, CA 94596-5318
- **Phone:** (925) 295-4000
## Medicare
- **Medicare:** Enrolled (PECOS); accepts Medicare assignment
- **Ordering & referring:** eligible for Part B labs & imaging, durable medical equipment, home health, power mobility devices
- **Bills Medicare through:** Permanente Medical Group Inc (NPI 1235226531, Richmond, CA), under Medicare reassignment (form CMS-855R) · CMS Revalidation Reassignment List, October 2026 release
- **Medical school:** Stanford University School Of Medicine, class of 1993
## Record status
- **NPPES last updated:** December 13, 2021
- **Other identifiers:** Medicaid 00G858130 (CA)
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Source: [NPI Profile](https://npiprofile.com/npi/1013095108) · Data from the CMS NPPES public registry.