Which block on the CMS-1500 form is used to indicate whether lab tests were performed by a different entity than the one billing?

Block 20 on the CMS-1500 form is utilized to indicate whether lab tests were performed by a different entity than the one submitting the claim for payment. This block specifically requests information on services performed by outside providers or entities to ensure proper processing of the claim. It allows insurers to understand who completed the service and can facilitate appropriate reimbursement processes. Accurately filling out this block is crucial when services are rendered by an independent laboratory, as it helps clarify the relationship between the billed services and the actual providers, enabling correct coverage determination and payment issuance.