What is required in Block 11 C?

Block 11 C of the CMS-1500 form is specifically designated for the entry of the nine-digit payer ID number of the primary insurer. This number is crucial for the processing of the claim, as it helps healthcare providers and payers quickly identify the specific insurance company responsible for payment. The use of a standard identifier streamlines the administrative process, allowing for faster claim processing and reducing the likelihood of errors during billing.

The other options provided do not belong in Block 11 C: the employer's address is not relevant to this section, recommendations from the insured do not pertain directly to the claim processing, and Medigap service details are typically recorded elsewhere on the claim form. Thus, accurately entering the payer ID in Block 11 C is essential for the drug of the claim's processing and ultimately for the provider's reimbursement.