Which item must be recorded in Block 1 on a CMS-1500 claim form?

• A. The patients mailing address
• B. The insureds social security number
• C. The patients Medicare Health Insurance Claim Number (HICN)
• D. The providers tax ID number

Answer: (C)

Block 1 is where the insured’s identification number goes. For Medicare claims, that identifier is the patient’s Medicare Health Insurance Claim Number (HICN). Placing the HICN in Block 1 ensures the claim can be correctly matched to the beneficiary’s Medicare records and processed accurately. The other items don’t belong in this first block: the patient’s mailing address is captured with other demographic details, the insured’s social security number is not used on CMS-1500 due to privacy and standard practice, and the provider’s tax ID number belongs in the provider-identifying sections rather than Block 1.