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WILLIAM J TSAI MD INC
NPI 1114277738
Internal Medicine in Irvine, CA

Active since September 11, 2012
19742 MACARTHUR BLVD, SUITE 101, IRVINE, CA 92612(949) 955-0202(949) 955-0203 Get Directions Write a Review

NPPES record last updated: September 11, 2012. Verified against the NPPES registry weekly; last sync: October 25, 2026.

About William J Tsai Md Inc NPPES

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

WILLIAM J TSAI MD INC (NPI 1114277738) is a healthcare organization registered as an internal medicine in Irvine, California and active in the NPI registry since September 2012. The organization lists William Jen Tsai, Pres/ceo, as its authorized official.

NPPES Registry Identity

NPI1114277738
Entity TypeOrganization
Primary Taxonomy207R00000X
Legal Business NameWILLIAM J TSAI MD INC
Location Address19742 MACARTHUR BLVD, SUITE 101Irvine, CA 92612-2432
Mailing Address19742 Macarthur Blvd, Suite 101Irvine, CA 92612-2432 · (949) 955-0202 · Fax (949) 955-0203
Phone(949) 955-0202
Fax(949) 955-0203
Organization SubpartNo
Authorized OfficialWilliam Jen TsaiPres/ceo · (949) 955-0202
Enumeration DateSeptember 11, 2012
✔ NPI 1114277738 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 · A71679
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.
19742 MACARTHUR BLVD, Irvine, CA 92612
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Other Identifiers 3

Medicare UPINH29939CA
Medicaid00A716790CA
Medicare PINA71679CA

Group Practice 1

Group TaxonomyThis provdier is a business group of one or more individual practitioners, all of who practice with the same area of specialization.193400000X SINGLE SPECIALTY GROUP

Medicare Participation & PECOS CMS

Medicare enrollment and the clinicians who bill Medicare through this organization, from CMS.

Medicare Enrollment Status

✔

Enrolled in Medicare (PECOS)

William J Tsai Md Inc is registered in the CMS Provider Enrollment, Chain and Ownership System (PECOS).

Clinicians Billing Medicare Through This Organization

Medicare enrollment records show 1 clinician reassigns Medicare billing to William J Tsai MD Inc, which bills Medicare for the services this clinician delivers.

Clinician (1)

William Tsai, M.D.
Internal Medicine
NPI 1952356560
19742 MACARTHUR BLVD STE 101
Irvine, CA 92612
(949) 955-0202
✔ PECOS✔ Accepts MedicareSame address

Source: CMS Revalidation Reassignment List, October 2026 release. Reassignment records can lag staffing changes; confirm a current affiliation with the organization.

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 J Tsai MD Inc's NPI number?

The NPI number for William J Tsai MD Inc is 1114277738. It was assigned to this organization in the NPPES registry on September 11, 2012.

Where is William J Tsai MD Inc located?

William J Tsai MD Inc is located at 19742 Macarthur Blvd Suite 101, Irvine, CA 92612. The listed phone number is (949) 955-0202.

What is William J Tsai MD Inc's specialty?

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

Is William J Tsai MD Inc enrolled in Medicare?

Yes. William J Tsai MD Inc is registered in the Medicare PECOS enrollment system.

How many clinicians bill Medicare through William J Tsai MD Inc?

According to the CMS Revalidation Reassignment List (October 2026 release), 1 clinician (Internal Medicine) reassigns their Medicare billing to William J Tsai MD Inc. A 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 the clinician's services. Reassignment records can lag staffing changes; confirm a current affiliation with the organization.

When was this NPI record last updated?

The NPPES record for William J Tsai MD Inc was last updated on September 11, 2012. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 14 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.