Are NPI numbers public?

Yes. NPI numbers are public federal identifiers in CMS NPPES. This page shows the public NPPES facts Fonteum has for NPI 1558420661: provider name, entity type, taxonomy, practice location, enumeration date, last-updated date, and source snapshot date. It does not include patient information.

What does the NPI record show for William Chen?

William Chen (NPI 1558420661) appears in CMS NPPES as ophthalmologist in Irvine, CA. NPPES is administrative identity data submitted to CMS by providers and organizations; this page displays the source snapshot date as 2026-05-06.

Does this page assign a provider score?

No derived score is assigned on this provider page. NPPES is an identity registry; when a CMS QPP MIPS value is available, Fonteum displays that public CMS value with its source, and absence of a MIPS value is not a quality signal.

Does no exclusion match amount to a clearance?

Coverage is indeterminate, so this page makes no negative exclusion determination. This is not a clearance; check the current issuing-agency lists.

Where does the provider data come from?

The identity fields come from CMS NPPES. Additional sections appear only when a public source has a matching row, such as CMS PECOS, CMS Open Payments, Medicare Part D, CMS QPP MIPS, OIG LEIE, or state Medicaid exclusion lists. Source and date metadata appears where the response supplies it; unavailable dates are labeled.

William Chen — NPI 1558420661: exclusion status

Name: Provider record — NPI 1558420661 (William Chen)
Creator: Fonteum
License: https://www.usa.gov/government-works

Built on the authoritative federal record

The primary sources, named on every page.

These are the federal agencies whose public datasets Fonteum ingests and attributes — the issuing authorities, not customers or partners. Every figure on the site links back to one of them.

CMS
HHS-OIG
HRSA
FDA
NLM
NUCC
Census
BLS
BEA

See the full source registry, with license and refresh cadence for each →

Reproducible by design

Published figures name their source and date.

Source and date

Published research identifies its government file and observation date. Source-file SHA-256 coverage is disclosed separately; facts do not currently link deterministically to signatures.

Reproducible SQL

Each study ships the exact query behind its figures, run against the same dated copy of the federal file we used. Re-run it yourself.

Daily observations

The platform records table row counts daily. Those observations detect local drift; they do not imply that an upstream publisher released or Fonteum ingested new data that day.

Named medical review

Reviewed by Jennifer Montecillo, MD, medical reviewer. Non-practicing medical reviewer.

Read the full provenance and attestation methodology →

Request access

William Chen — NPI 1558420661: exclusion status — Fonteum

Cross-source identity

Sources that publish this NPI

National Provider Identifier 1558420661 appears in the source rows shown below. Sources that do not publish NPI use their own identifiers and are not treated as deterministic NPI matches. Chips show response-supplied dates when available; otherwise they are labeled date unavailable.

NPPES

Federal sources carrying NPI 1558420661
Federal source	Key	What it provides	Source & date
CMS NPPES	NPI 1558420661	Registry identity — ophthalmologist, taxonomy 207W00000X	Source:CMS NPPESSnapshot 2026-05-06
CMS Medicare Part D	NPI 1558420661	1 drugs prescribed, 2024	Source:CMS Part DSnapshot DY2024

Prescribing

Medicare Part D prescribing

Prescriptions written under Medicare Part D, aggregated by drug across the program. Totals reflect claims paid, not patients treated.

Part D claims

$448

Total drug cost

Distinct drugs

Beneficiaries

Highest-cost drugs prescribed
Drug	Claims	Drug cost
Neomycin-Polymyxin-Dexameth(Neomycin/Polymyxin B/Dexametha)	48	$448

Source:CMS Medicare Part DSnapshot DY2024

William Chen

Public NPPES answers

Are NPI numbers public?

What does the NPI record show for William Chen?

Does this page assign a provider score?

Does no exclusion match amount to a clearance?

Where does the provider data come from?

Sources that publish this NPI

Medicare Part D prescribing

MIPS quality score

Standing

Who owns, operates, or is affiliated with this provider

Retained versions for this record

William Chen

Public NPPES answers

Are NPI numbers public?

What does the NPI record show for William Chen?

Data-use and correction resources.

Does this page assign a provider score?

Does no exclusion match amount to a clearance?

Where does the provider data come from?

Sources that publish this NPI

Medicare Part D prescribing

MIPS quality score

Standing

Who owns, operates, or is affiliated with this provider

Retained versions for this record

Context for this record