NPI Luhn Check-Digit Validator / Generator

NPI Luhn check-digit validation (10 digits) or generation from a 9-digit base, per the CMS/ISO 80840 prefix rule.

Open the tool → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.

Example

NPI: 1234567893

Result: NPI 1234567893 is valid: the recomputed Luhn check digit is 3.

The tool opens with these values already filled in. Replace them with your own.

What you enter

NPI (10 digits to validate, or a 9-digit base to generate)

How this is calculated

45 CFR 162.406 (National Provider Identifier): the NPI check digit is computed by the Luhn algorithm (ISO/IEC 7812) over the 9-digit identifier prefixed with the 80840 issuer prefix. CMS NPI standard -- format/check-digit validation only, not an NPPES enrollment check. Read the source ↗

A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.