What is required in Block 24J of the CMS-1500 form?

• A. The provider's license number.
• B. The tax ID number.
• C. The NPI number of the rendering provider.
• D. The facility's address.

Answer: (C)

Block 24J is where you enter the NPI of the rendering provider—the clinician who performed the service. The National Provider Identifier is a unique 10-digit number assigned under HIPAA to identify individual practitioners in electronic health transactions. Placing the rendering provider’s NPI in this field ensures the payer can correctly link the service to the right provider, which supports accurate adjudication and auditing. In clinical claims, NPIs are the standard identifier used by payers, replacing older identifiers like license numbers for this purpose. The license number isn’t used here because it’s a credentialing detail, not the billing identifier; the tax ID belongs to the billing entity and appears in other claim fields; the facility address is captured elsewhere as the service location, not in this field.