Which CMS-1500 Block requires entry of either the Social Security number (SSN) or the employer tax identification number (EIN)?

In the context of the CMS-1500 form, Block 25 is specifically designated for the entry of the provider's tax identification number (TIN), which includes either the Social Security number (SSN) for individual providers or the Employer Identification Number (EIN) for organizations or group practices. This block is important because it allows the payer to correctly identify the provider for billing and reimbursement purposes, ensuring that payments are directed to the correct entity.

Understanding the importance of accurate identification information is crucial in health insurance billing, as it directly affects claim processing and the timeliness of reimbursements. Thus, filling out Block 25 correctly with either the SSN or EIN is essential for compliance with the billing requirements of health insurance carriers.