NPI Portal NPI Lookup & Verification

Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Dr. William Seng Tan, D.O.

Family Medicine Physician in Olympia Fields, IL · enumerated 2014 · practices at William Seng Tan, Sc.

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

National Provider Identifier

1891112306

Verified

See something wrong? Report a correction

Registry record

Entity type Individual (Type 1)
Name Dr. William Seng Tan
Credential D.O.
Sex Male
Practice address 20060 Governors Dr Ste 204, Olympia Fields, IL, 60461
Phone (708) 283-8300
Fax (708) 283-9245
Enumeration date Mar 21, 2014
Last updated in NPPES Dec 25, 2021

Taxonomy & licenses

207Q00000X Family Medicine Physician Allopathic & Osteopathic Physicians · License 036144064 (IL) Primary
DO · Doctor of Osteopathic Medicine: A fully licensed physician trained in osteopathic medical schools, with the same practice rights as an MD. About the DO 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

What is the NPI number for William Tan?
The National Provider Identifier (NPI) for William Tan is 1891112306, a Type 1 (individual) record in the CMS NPPES registry.
Where does William Tan practice?
The practice location on file with NPPES is in Olympia Fields, IL. Providers can have multiple locations; NPPES lists the primary practice address.

Other providers at this practice address

Browse all →

Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2021-12-25.