Which action must be taken to ensure ICD-10-CM diagnoses are captured on the CMS-1500 form?

• A. Ensure ICD-10-CM diagnoses are entered in Block 21.
• B. Enter only the primary diagnosis in Block 18.
• C. Leave Block 21 blank if the patient has a diagnosis.
• D. Enter the patient's SSN in Block 21.

Answer: (A)

ICD-10-CM diagnoses belong in Block 21 because this field is specifically designated for listing the diagnoses that justify the services on the claim. Entering the codes here ensures the payer has the clinical basis for the encounter and can properly process the reimbursement. You can list multiple diagnoses in Block 21, typically starting with the primary diagnosis and adding secondaries as needed, so the complete diagnostic justification travels with the claim. Placing diagnoses elsewhere, or leaving Block 21 blank, would fail to provide the necessary diagnostic information and can lead to claim denial. Also, Block 21 is not for personal identifiers like the patient’s SSN; that would be inappropriate and a privacy risk.