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Recently Updated NPI Information — some details in this NPI profile have been updated in the NPI registry within the last 60 days.

WILLIAM L. MATZNER M.D., PH.D.
NPI 1306905716
Internal Medicine in Simi Valley, CA

Active since December 08, 2006
543 COUNTRY CLUB DR # B125, SIMI VALLEY, CA 93065(805) 578-7000 Get Directions Write a Review

NPPES record last updated: September 27, 2026. Verified against the NPPES registry weekly; last sync: October 11, 2026.

Record update history: Sep 27, 2026, Dec 15, 2015 (2 updates tracked since 2015).

About William L. Matzner M.d., Ph.d. NPPES

Official registry information on file with the National Plan and Provider Enumeration System.

WILLIAM L. MATZNER M.D., PH.D. (NPI 1306905716) is an individual internal medicine provider in Simi Valley, California, licensed in California (AO43053) and active in the NPI registry since December 2006.

NPPES Registry Identity

NPI1306905716
Entity TypeIndividualMale
Primary Taxonomy207R00000X
Provider Legal NameWILLIAM L. MATZNERCredential: M.D., PH.D.
Location Address543 COUNTRY CLUB DR # B125Simi Valley, CA 93065-0637
Mailing Address543 Country Club Dr # B125Simi Valley, CA 93065-0637 · (805) 578-7000 · Fax (805) 578-7005
Phone(805) 578-7000
Sole ProprietorYes
Enumeration DateDecember 8, 2006
Last NPPES UpdateSeptember 27, 20262 updates tracked since enumeration
NPPES CertifiedSeptember 27, 2026
✔ NPI 1306905716 is a valid, active identifier and passes the ISO check-digit test.

Specialties & Licenses

★ Primary SpecialtyInternal MedicineAllopathic & Osteopathic Physicians
Taxonomy Code207R00000X
License✔ Licensed in CA · AO43053
Definition
A physician who provides long-term, comprehensive care in the office and the hospital, managing both common and complex illness of adolescents, adults and the elderly. Internists are trained in the diagnosis and treatment of cancer, infections and diseases affecting the heart, blood, kidneys, joints and digestive, respiratory and vascular systems. They are also trained in the essentials of primary care internal medicine, which incorporates an understanding of disease prevention, wellness, substance abuse, mental health and effective treatment of common problems of the eyes, ears, skin, nervous system and reproductive organs.
543 COUNTRY CLUB DR # B125, Simi Valley, CA 93065
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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 Matzner's NPI number?

The NPI number for William Matzner is 1306905716. It was assigned to this individual provider in the NPPES registry on December 8, 2006.

Where is William Matzner located?

William Matzner practices at 543 Country Club Dr # B125, Simi Valley, CA 93065. The listed phone number is (805) 578-7000.

What is William Matzner's specialty?

The primary specialty registered for this NPI is Internal Medicine with taxonomy code 207R00000X.

When was this NPI record last updated?

The NPPES record for William Matzner was last updated on September 27, 2026. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 17 days 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.