HCFA-1500 Box 25 - Federal Tax ID Number

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August 25, 2025

On the HCFA-1500 form, Box 25 is labeled “Federal Tax ID Number” and is used to report the billing provider’s tax identification number. This may be either an Employer Identification Number (EIN) or the provider’s Social Security Number (SSN), depending on how the provider is registered with the IRS and the payer.

Tip: Be sure to enter the correct tax ID and check the appropriate box (EIN or SSN) to indicate the type of number reported. In most cases, providers use their EIN, so the EIN box will be checked. Using an incorrect or mismatched ID may cause claim rejections or delays in payment.

In our example below, the provider reported a Tax ID of 123558899 with the EIN box checked.

HCFA-1500 Box 25 - Federal Tax ID Number

In the X12 837P 5010 transaction, Box 25 data maps to the following:

  • 2010AA REF02 – Billing Provider Tax Identification Number

Sample 837P (5010) – Box 25 Mapping

> Billing Provider Tax ID (2010AA) REF*EI*123558899~

Segment Breakdown:

  • REF01: Qualifier (EI = Employer Identification Number, SY = Social Security Number)
  • REF02: Billing provider’s tax ID (e.g., 123558899)

Note: The tax ID in Box 25 must exactly match the IRS-registered identifier on file with the payer. Incorrect values can cause claim rejection or payment delays.

For additional information on the X12 837 standard, please refer to the official implementation guides published by X12.

HCFA-1500 Form Box Locations

Grab a sample of the HCFA-1500 claim form here - HCFA 02/12 Claim Form


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