Which detail must NOT be included if Medicare is the primary payer in Block 4?

When filling out Block 4 on the CMS-1500 form, if Medicare is the primary payer, the correct protocol is to include specific information regarding the patient and their relationship to Medicare. The inclusion of the patient's last name, the patient's Medicare ID, and their relationship to the insured is essential in ensuring accurate processing of claims.

However, the name of the insured is not necessary to include in this specific instance. This is because when Medicare is the primary payer, the patient's own information, such as their Medicare ID, suffices and eliminates the need for the name of the insured if it differs from the patient (as in cases where the patient is covered by another individual's Medicare plan, like a spouse). Therefore, option B is correct because the name of the insured does not need to be present in Block 4 when Medicare is responsible for primary payment.