HCFA-1500 Box 1a - Insured's ID Number

On the HCFA-1500 form, box 1a is designated for the insured's ID Number. This will normally be the insured id number for the subscriber of the claim. While not typical, some payers may assign unique identification numbers to each enrollee/dependent and require the specific number of the member receiving services instead of the insured's number. See the members insurance card and/or use an Eligibility check service to verify the information prior to populating.

In our example below, we populated box 1a with 'ABC12345678'. The formatting of the number will vary. Typically, spaces/hyphens are removed from the id number.

So far, we talked about what the insured's id number box on the HCFA form is and the information used to populate this location. In the next section, we'll briefly discuss the insured's id number box in relation to the X12 837 format.

In the X12 837 format, the insured's id number box information goes in the 2010BA Subscriber Name Loop - NM1 segment. More specifically, the HCFA Box 1a insured's id number data goes in the NM109, which is also known as the Subscriber Primary Identifier.

The example below shows the 2010BA Subscriber Name Loop - NM1 segment. In our sample, we have the value ABC12345678 for the NM109. For additional information on the X12 837 format, we strongly recommend consulting the official X12 materials.

Sample 837P (5010) - 2010BA - Subscriber Name

HCFA-1500 Form Box Locations

• HCFA-1500 Box 0 - Carrier Block
• HCFA-1500 Box 1 - Insurance Type
• HCFA-1500 Box 1a - Insured's ID Number [You are Here]
• HCFA-1500 Box 2 - Patient's Name
• HCFA-1500 Box 3 - Patient's Birth Date and Sex