What is typically found in Block 21 of the CMS-1500 claim form?

Block 21 of the CMS-1500 claim form is designated for diagnosis codes. This section is critical because it allows healthcare providers to specify the patient’s diagnoses relevant to the services rendered. By listing the diagnosis codes here, it enables insurance companies to understand the medical necessity of the services provided and facilitates the adjudication process.

The formatting in Block 21 adheres strictly to coding guidelines, and the codes entered here directly correlate with the Current Procedural Terminology (CPT) codes used in Block 24, ensuring a clear link between the provided services and the reasons for those services based on the given diagnoses. This linkage is essential in claims processing, as it provides the insurance payer with the context needed to approve the claim.