WILLIAM D. MOSIER, M.D., INC., A PROFESSIONAL MEDICAL CORPORATION
WILLIAM D. MOSIER, M.D., INC., A PROFESSIONAL MEDICAL CORPORATION is an organization registered with the National Plan and Provider Enumeration System (NPPES) under NPI 1003476508, based in Fullerton, CA. It is classified under Ophthalmology Physician.
Getting there
Here is what surrounds this office in Fullerton, based on OpenStreetMap data collected Sep 29, 2026. Parking is available about 0.21 mi away. The nearest transit stop is 915 ft away, served by Harbor-Valencia Mesa. A pharmacy sits 925 ft from the entrance (King's Pharmacy), which helps if you leave with a prescription. If you arrive early, there is a coffee shop 610 ft away.
Getting here and what is nearby
Gas station 76 438 ft ~2 min
Transit Harbor-Bastanchury 496 ft ~2 min
Coffee The Boba Place 555 ft ~3 min
Coffee Eggspresso 610 ft ~3 min
Parking 620 ft ~3 min
Pharmacy CVS Pharmacy 610 ft ~3 min
Transit Harbor-Bastanchury 698 ft ~3 min
Parking 750 ft ~3 min
Transit Harbor-Valencia Mesa 915 ft ~4 min
Pharmacy King's Pharmacy 925 ft ~4 min
Parking 0.21 mi ~5 min
Distances are straight‑line estimates — walking routes may be longer. Hours and phone numbers can change; call ahead to confirm.
Credentials and Medicare
NPPES does not list a state licence number for this record. That is not unusual — organizations and some provider types are not required to file one. Verify current licensure with the relevant state board before care.
- Status
- Approved
- Provider type
- Part B Supplier - Clinic/group Practice
- PAC ID
- 2365877958
- Enrollment ID
- O20200108000962
Medicare enrolment is recorded as approved under the provider type Part B Supplier - Clinic/group Practice. Being enrolled means the provider can bill Medicare; it does not tell you whether they are currently accepting new Medicare patients. Call the office to confirm.
What Ophthalmology covers
An ophthalmologist has the knowledge and professional skills needed to provide comprehensive eye and vision care. Ophthalmologists are medically trained to diagnose, monitor and medically or surgically treat all ocular and visual disorders. This includes problems affecting the eye and its component structures, the eyelids, the orbit and the visual pathways. In so doing, an ophthalmologist prescribes vision services, including glasses and contact lenses. NUCC Health Care Provider Taxonomy, code 207W00000X
The taxonomy records how the provider classifies their own practice. It does not confirm which conditions they currently treat, whether they are accepting new patients, or which insurance they take — call the office for that.
Full NPPES record
An NPI-2 identifies an organization — a clinic, hospital, group practice, laboratory, or supplier. Individual clinicians working there hold their own NPI-1 numbers separately, so a bill may reference both.
| NPI | 1003476508 valid check digit |
|---|---|
| Entity type | Organization (NPI-2) |
| Enumeration date | Jun 17, 2019 |
| Last updated | Nov 2, 2023 |
| Status | Active |
| Practice address |
265 LAGUNA RD Fullerton, CA 92835 (714) 871-2570 Fax (714) 441-2020 |
Number check
How the check works, step by step
Every NPI carries a Luhn check digit — the same scheme used on credit cards. CMS prefixes the number with 80840 before computing it, which marks it as a US health identifier.
| Digit | 8 | 0 | 8 | 4 | 0 | 1 | 0 | 0 | 3 | 4 | 7 | 6 | 5 | 0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 0 | 0 | 3 | 8 | 7 | 3 | 5 | 0 |
Sum = 52 · next multiple of 10 = 60 · check digit = 8 · actual last digit = 8
A valid check digit only means the number is well-formed. It does not mean the provider is licensed, active, or in good standing — those are separate questions answered by the sections above.