The Generic CDA Domain Message Specification contains details on the "on-the-wire" format for CDA payloads. The "on-the-wire" format is the actual payload structure that is sent to a recipient. The Generic CDA Domain Message Specification documents two "on-the-wire" CDA formats. The first is for use over the Transaction Messaging System (TMS) when using TMS wrappers, this is documented in the Generic CDA Domain Message Specification as "NPfIT CDA RMIM - POCD_MT000001UK04". The second is used for non-TMS usage and is documented in the Generic CDA Domain Message Specification as "NHS CDA RMIM - POCD_MT000002UK01".