NPI Validator & Number Validation

What is an NPI?

The National Provider Identifier (NPI) is a unique 10-digit identifier issued by the Centers for Medicare & Medicaid Services (CMS) to every healthcare provider and organization in the United States. It's required on every HIPAA-covered electronic transaction — CMS-1500, UB-04, ADA J430D, and their EDI 837 equivalents.

• NPI-1: individual providers (doctors, dentists, PAs, NPs, therapists)
• NPI-2: organizations (hospitals, clinics, group practices, DME, pharmacies)
• Issued and maintained by CMS NPPES — the National Plan and Provider Enumeration System
• Required on Boxes 24J / 31-33 of the CMS-1500 and Boxes 48-58 of the ADA J430D

How the NPI checksum works

The 10th digit of every NPI is a Luhn (ISO/IEC 7812) check digit calculated over the first 9 digits, prefixed with 80840 — the CMS issuer identifier for the US health-industry range.

# Example: 1437702123
1. Prefix first 9 digits with '80840'
   → 80840 143770212
2. Reverse and double every 2nd digit
3. If a doubled digit > 9, subtract 9
4. Sum every digit
5. check = (10 - (sum mod 10)) mod 10
6. Compare with NPI's 10th digit
   → matches 3 → valid ✓

A valid checksum doesn't guarantee the NPI is real — it only means the number is mathematically well-formed. Always confirm against the CMS NPPES registry (this tool does both, in one call).