Medical Billing Resource
NPI / TIN / EIN Resource Center
Understand the difference between provider identifiers and tax identifiers — and where they belong on a CMS-1500 claim.
Reviewed September 2026 · Educational reference — verify payer and program requirements.
Provider and tax identifier guides
These pages separate the roles that are often mixed together in search queries: provider identity, billing identity, rendering identity and federal tax identity.
NPI vs TIN
An NPI identifies a health care provider in HIPAA administrative transactions; a TIN identifies a taxpayer/business for tax reporting. They are not interchangeable.
NPI vs EIN
An NPI is a provider identifier; an EIN is a federal tax identifier for a business or entity. A billing workflow may require both in different fields.
Where Does the TIN Go on CMS-1500?
CMS-1500 Box 25 is the federal tax ID field. The form distinguishes SSN or EIN as applicable.
Where Does the NPI Go on CMS-1500?
NPIs can appear in several roles, including referring/ordering information, rendering provider service lines, service facility and billing provider fields.
Billing NPI vs Rendering NPI
The billing provider is the entity submitting the claim; the rendering provider is the individual who performed the service. Their NPIs may differ.
CMS-1500 Box 25 Tax ID Guide
Box 25 reports the federal tax ID of the billing entity and indicates whether the identifier is an SSN or EIN as applicable.
CMS-1500 Box 33a Billing NPI
Box 33a is the billing provider NPI field on the CMS-1500 form.