HCFA-1500 Box 26 - Patient's Account No.

On the HCFA-1500 form, Box 26 is labeled “Patient’s Account No.” and is used to report your internal, provider-assigned control number for the claim (often called the patient control number). This value helps you match payments and remittance advice back to your practice management system.

Tip: Use a unique, non-PHI identifier (letters, numbers, and limited symbols are acceptable per payer rules). This reference will be echoed on payer responses (e.g., the 835 ERA).

In our example below, the provider reported F-12354-01 as the patient account number.

In the X12 837P 5010 transaction, Box 26 maps to CLM01 in the 2300 Claim Information Loop.

Sample 837P (5010) – Box 26 Mapping

Segment Breakdown (focus on Box 26):

• CLM01: Patient Control Number / Patient’s Account Number (e.g., F-12354-01)
• Other CLM elements shown are illustrative and not driven by Box 26.

Note: Keep the Box 26 value consistent with your internal records. Do not include PHI (e.g., SSN). Most payers return this number on the 835 remittance to aid reconciliation.

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

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
• HCFA-1500 Box 2 - Patient's Name
• HCFA-1500 Box 3 - Patient's Birth Date and Sex
• HCFA-1500 Box 4 - Insured's Name
• HCFA-1500 Box 5 - Patient's Address
• HCFA-1500 Box 6 - Patient Relationship to Insured
• HCFA-1500 Box 7 - Insured's Address
• HCFA-1500 Box 8 - Reserved For NUCC Use
• HCFA-1500 Box 9 - Other Insured's Name
• HCFA-1500 Box 9a - Other Insured's Policy or Group Number
• HCFA-1500 Box 9b - Reserved For NUCC Use
• HCFA-1500 Box 9c - Reserved For NUCC Use
• HCFA-1500 Box 9d - Insurance Plan Name or Program Name
• HCFA-1500 Box 10 - Is Patient's Condition Related To
• HCFA-1500 Box 10d - Claim Codes
• HCFA-1500 Box 11 - Insured's Policy Group or FECA Number
• HCFA-1500 Box 11a - Insured's Date of Birth and Sex
• HCFA-1500 Box 11b - Other Claim ID
• HCFA-1500 Box 11c - Insurance Plan Name or Program Name
• HCFA-1500 Box 11d - Is There Another Health Plan
• HCFA-1500 Box 12 - Patient's or Authorized Person's Signature
• HCFA-1500 Box 13 - Insured's or Authorized Person's Signature
• HCFA-1500 Box 14 - Date of Current Illness, Injury, Pregnancy (LMP)
• HCFA-1500 Box 15 - Other Date
• HCFA-1500 Box 16 - Dates Patient Unable to Work in Current Occupation
• HCFA-1500 Box 17 - Name of Referring Provider or Other Source
• HCFA-1500 Box 17a - Other ID
• HCFA-1500 Box 17b - NPI
• HCFA-1500 Box 18 - Hospitalization Dates Related to Current Services
• HCFA-1500 Box 19 - Additional Claim Information
• HCFA-1500 Box 20 - Outside Lab Charges
• HCFA-1500 Box 21 - Diagnosis or Nature of Illness or Injury
• HCFA-1500 Box 22 - Resubmission Code and Original Reference Number
• HCFA-1500 Box 23 - Prior Authorization Number
• HCFA-1500 Box 24a - Date(s) of Service
• HCFA-1500 Box 24b - Place of Service
• HCFA-1500 Box 24c - EMG
• HCFA-1500 Box 24d - Procedures, Services, or Supplies
• HCFA-1500 Box 24e - Diagnosis Pointer
• HCFA-1500 Box 24f - Charges
• HCFA-1500 Box 24g - Days or Units
• HCFA-1500 Box 24h - EPSDT/Family Plan
• HCFA-1500 Box 24i - Rendering Provider ID Qualifier
• HCFA-1500 Box 24j - Rendering Provider ID
• HCFA-1500 Box 25 - Federal Tax ID Number
• HCFA-1500 Box 26 - Patient's Account No. [You are Here]
• HCFA-1500 Box 27 - Accept Assignment
• HCFA-1500 Box 28 - Total Charge
• HCFA-1500 Box 29 - Amount Paid
• HCFA-1500 Box 30 - Rsvd for NUCC Use
• HCFA-1500 Box 31 - Signature of Physician or Supplier Including Degrees or Credentials
• HCFA-1500 Box 32 - Service Facility Location Information

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