What is the purpose of Block 21 in the Physician/Supplier Information section?

• A. To enter ICD-10-CM diagnosis code(s).
• B. To enter procedure code(s).
• C. To enter patient's demographics.
• D. To store billing provider's tax ID.

Answer: (A)

Block 21 is where ICD-10-CM diagnosis codes are entered. These codes describe the patient’s condition or the reason for the encounter and justify why the services were provided. They link directly to each service line to establish medical necessity, showing that the CPT/HCPCS procedure codes billed have a supported diagnosis. Other information like patient demographics or the billing provider’s tax ID belongs in different sections, and the actual procedure codes appear in the service line area rather than Block 21. Typically you start with the primary diagnosis and add secondary ones as needed.