Medical Billing Resource
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.
Reviewed September 2026 · Educational reference — verify payer and program requirements.
Short answer
Box 25 reports the federal tax ID of the billing entity and indicates whether the identifier is an SSN or EIN as applicable.
How to apply this on a claim
Start with the provider role and the field label rather than the number itself. A billing provider, rendering provider, referring/ordering provider and service facility can each have different reporting locations. Federal tax ID information is reported separately from NPI information.
Verification checklist
- Confirm the billing entity and provider role.
- Match identifiers to current enrollment and payer records.
- Do not place an EIN/TIN in an NPI field or an NPI in a tax-ID field.
- Verify payer-specific requirements for secondary identifiers.
NPI validator note: the free tool checks the 10-digit NPI format/check digit. It does not replace verification of provider identity or payer enrollment.