Box 21 identifies the diagnoses or conditions related to the services on a CMS-1500 claim. The form provides space for as many as 12 diagnosis codes, labeled A through L.
How Box 21 works
- Enter current ICD-10-CM diagnosis codes that are supported by the patient record.
- List the diagnoses in the order required by the payer and the claim circumstances.
- Use the letter assigned to each diagnosis when completing the diagnosis pointer in Box 24E.
Diagnosis pointers in Box 24E
Box 24E does not repeat the diagnosis code. It uses the corresponding letter or letters from Box 21 to show which diagnosis supports each service line. Review every service line to make sure its pointers refer to the intended diagnosis entries.
Before submitting
Verify code validity for the date of service, confirm that the documentation supports the code selection, and follow payer-specific rules for sequencing and the number of pointers allowed on a service line.
Billing reminder: Payer and program requirements vary. Confirm the current instructions for the payer receiving the claim.