1. Coding system used by the physician’s office does not match the coding system used by the insurance company receiving the claim. The insurance company computer system converts the procedure code submitted to the closest code in use, which is usually down one level from the submitted code, generating decreased payment. Sometimes downcoding may occur when the diagnosis code does not support the level of care. 2. Selecting procedure codes at a lower level than the medical service requires or documentation supports. Also called undercoding . Also see penalized claim.