Guides

Plain-English references on NPI numbers, taxonomy codes, and the official U.S. provider registry. When you’re ready, search the registry.

What is an NPI number?

Format and check digit, Type 1 vs Type 2, who needs one, and how to look one up.

NPI vs. taxonomy vs. PECOS vs. CLIA

Four identifiers, four jobs — a clear comparison of what each one tells you.

Provider taxonomy codes explained

How NUCC specialty codes are built, primary vs secondary, and common codes.

How to verify a provider’s NPI

Validity vs verification, what to confirm, and verifying at scale.

How to read an NPPES provider record

A field-by-field walkthrough and the gotchas to watch for.

Bulk NPI validation for billing & credentialing

Validate rosters of NPIs at scale to prevent denials and compliance gaps.

Inside the NPPES database

How the raw government provider data is structured — and why it’s hard to use.