Background: The Section in the FHIR Specification that the commenter is referencing : 13.0.10 Attachments - Supporting Information  There is often a need to provide supporting information, commonly referred to as  attachments , to document the need for a service and/or to confirm that the good or service was authorized or rendered. This information may be in many forms, including: scanned documents, PDFs, word processing files, X-Rays, images, CDAs and FHIR Resources. Supporting information may be provided, as a reference or the actual material, to support the  Claim  (complete claim or Preauthorization) or  ExplanationOfBenefit  in a variety of manners:   Included : in the .supportingInfo section; Unsolicited : in a  Communication  which refers to the Claim or Explanation of Benefit; or Solicited : in a  Communication  in response to a  CommunicationRequest  from the insurer requesting more information; or Input : in the input parameters of a FHIR operation or Task.input element if a  Task  resource is used.   HIPAA requirements for attachments rule is that the standard must be compatible with existing X12 transactions (837,277). CDex Project will define a set of FHIR transactions that are compatible with these X12 transactions (277, 278).  In other words, CDex working with the PIE workgroup will add support for Attachments Request using FHIR based request (content to be added to CDex for Sept/ Ballot) specifically for the "solicited attachments" use case.   However, as documented in the Da Vinci HREX IG ( http://hl7.org/fhir/us/davinci-hrex/exchanging-request.html#request ), given the downsides associated with Requesting exchange using CommunicationRequest, CDex will be using a Task based approach instead.   We will create a tracker to suggest changes to the Financial Management Group page to expand the list of options and discourage the use of CommunicationRequest.