What Is an NPI Number?
A plain-language explanation of the National Provider Identifier: what it is, who assigns it, what its digits mean, and what it does and does not certify.
Reviewed
A National Provider Identifier, or NPI, is a 10-digit number the federal government assigns to identify a health care provider in standard electronic transactions. It is issued once, it does not expire on its own, and — outside of rare replacement cases — a provider keeps the same NPI for the rest of their career or the life of their organization.
The NPI is a HIPAA administrative standard, created under the Health Insurance Portability and Accountability Act's administrative simplification rules. The identifier itself, the entities that must obtain one, and the system that issues it are defined in federal regulation at 45 CFR Part 162, Subpart D.
Why a national identifier exists
Before the NPI, a health care provider often had a different identification number for every health plan, Medicare contractor, and state Medicaid program it dealt with. That patchwork made electronic billing error-prone and expensive to maintain. HIPAA's administrative simplification provisions replaced it with one identifier — the NPI — that every HIPAA-covered entity uses to identify a given provider in standard transactions such as claims, eligibility inquiries, and remittance advice.
Who is assigned an NPI
Two kinds of applicants receive an NPI, corresponding to the two NPI entity types:
- Individual providers (Entity Type 1) — human beings who furnish health care, such as physicians, nurse practitioners, dentists, and physical therapists.
- Organization providers (Entity Type 2) — hospitals, group practices, pharmacies, home health agencies, and other organizations that furnish health care, including individual practices that choose to enumerate the business itself in addition to the practitioner.
See NPI Type 1 vs Type 2 for how the two differ in practice, including what each entity type reports to NPPES.
A health care provider that is a HIPAA-covered entity — one who transmits any of the standard electronic transactions HIPAA defines, whether directly or through a billing service or clearinghouse — is required to obtain an NPI. Providers who are not otherwise covered by HIPAA may still apply for one voluntarily, and many do, because health plans and clearinghouses commonly expect an NPI regardless.
What the number itself is built from
An NPI is exactly 10 digits, numeric only, with no embedded meaning about the provider — no state code, no specialty, no birth year. The regulation is explicit that the NPI carries no intelligence: two providers in the same city with consecutive NPIs could have nothing else in common. The only structure in the number is arithmetic: the 10th digit is a check digit, calculated from the first nine digits using the Luhn (mod 10) algorithm after prefixing them with the constant 80840, the ISO/IEC 7812 issuer identifier CMS was assigned for this purpose.
That check digit is what lets software tell a well-formed NPI from a typo before ever querying a database. See How Does NPI Number Validation Work? for the full calculation, worked digit by digit.
| Property | Value |
|---|---|
| Length | 10 digits, numeric only |
| Format | NNNNNNNNNC (9 identifying digits + 1 check digit) |
| Check digit | Position 10, Luhn algorithm over 80840 + first 9 digits |
| Leading digit today | 1 (individual) or 2 (organization) |
| Reused after deactivation? | No — a deactivated NPI is retired, not reassigned |
What an NPI is not
An NPI identifies a provider for transaction purposes. It is not a license, not a board certification, and not a background check. CMS's own enumeration guidance is direct on this point: issuing an NPI does not verify or guarantee that the recipient is licensed or credentialed in any jurisdiction. Licensure is granted and monitored by state licensing boards, which are entirely separate from NPPES.
This distinction matters enough that it has its own guide: Does an NPI Mean a Provider Is Licensed?.
Where NPI records live
Every NPI, along with the identifying information the applicant reported, is recorded in the National Plan and Provider Enumeration System, or NPPES — the federal registry CMS operates. NPPES data is published for public download and searchable through CMS's own registry. See What Is NPPES? for how that system works and what it publishes.
NPI Registry — official CMS lookup — CMSSearch any NPI directly against the government's own registry.
Sources
- 45 CFR Part 162, Subpart D — Standard Unique Health Identifier for Health Care Providers — Electronic Code of Federal Regulations (eCFR). Accessed August 20, 2026.
- 45 CFR § 162.410 — Implementation specifications: Health care providers — Cornell Law School Legal Information Institute. Accessed August 20, 2026.
- NPI: What You Need to Know — CMS Medicare Learning Network. Accessed August 20, 2026.
- Requirements for National Provider Identifier (NPI) and NPI Check Digit — CMS. Accessed August 20, 2026.
- National Provider Identifier Standard (NPI) — CMS. Accessed August 20, 2026.