Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum Sole proprietor

Dr. William Reeves Tatomer, MD

Psychiatry Physician in San Mateo, CA · enumerated 2006.

Data current as of Jul 13, 2026 · sourced from CMS NPPES

National Provider Identifier

1104862689

Verified

See something wrong? Report a correction

Registry record

Entity type Individual (Type 1)

Name Dr. William Reeves Tatomer

Credential MD

Sex Male

Practice address San Mateo, CA, 94401

Phone (650) 342-4442

Fax (650) 342-8816

Enumeration date Jun 21, 2006

Last updated in NPPES Apr 16, 2010

Street address withheld: NPPES sole-proprietor addresses can be home addresses. See our data policy.

Taxonomy & licenses

2084P0800X Psychiatry Physician Allopathic & Osteopathic Physicians · License C35537 (CA) Primary

MD · Doctor of Medicine: A physician who completed medical school (allopathic medicine), residency training, and state licensure. About the MD credential

What is an NPI number?

A National Provider Identifier (NPI) is a unique 10-digit number that CMS assigns to every U.S. healthcare provider and organization under HIPAA. Type 1 NPIs identify individual providers; Type 2 NPIs identify organizations. The NPI appears on insurance claims, prescriptions, and credentialing paperwork, and never changes, even if the provider moves or changes specialty.

Read the full guide → Validate an NPI →

Frequently asked questions

Is this the official NPI registry?

No. NPI Portal is a private site built on public CMS NPPES data. The official registry is npiregistry.cms.hhs.gov, operated by CMS.

What specialty is William Tatomer?

William Tatomer is registered in NPPES with the primary taxonomy of Psychiatry Physician. The taxonomy code describes the provider's classification and area of specialization for claims and credentialing.

Other providers at this practice address

Browse all →

Jacqueline Koo Ophthalmology Physician · San Mateo, CA NPI 1528060308 Michael Stevens Rheumatology Physician · San Mateo, CA NPI 1932198793 Mary Dobbins Internal Medicine Physician · San Mateo, CA NPI 1407837693 Laboratory Corporation of America Clinical Medical Laboratory · San Mateo, CA NPI 1720060866 Peninsula Ultrasound, Mammography & Radiology Services Medical Group Radiology Clinic/Center · San Mateo, CA NPI 1871569525 Pacific Network Imaging, Inc. Nuclear Cardiology Physician · San Mateo, CA NPI 1982653598 Thomas Watters Nuclear Cardiology Physician · San Mateo, CA NPI 1508816596 Jack Bernstein Internal Medicine Physician · San Mateo, CA NPI 1457301384

Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2010-04-16.