Aside from the technical differences between CHIEF and CDS in terms of processing, connectivity and messaging structure, the customs declarations themselves differ in terms of data structure and content.
CDS declarations use Data Elements (up to 91) in place of the 68 SAD boxes referenced by CHIEF. This comparison immediately illustrates the more extensive data set requirement within CDS. Whilst some of the SAD boxes directly correlate to a corresponding Data Element, CDS introduces and mandates a number of new reporting requirements.
Additionally, where a correlation exists, it may be the case that CDS requires the data to be submitted in a different format so you will find there are a number of new code lists. Whilst there are many consistencies between key areas such as the majority of Documents, Licences and AI Statement Codes, there are also some which differ significantly, such as Goods Location codes.
One other key point to note is that CDS uses a new structure for Customs Procedure Codes. CHIEF has a fixed 7-digit CPC for a goods item whilst within CDS this is split onto two parts: a single 4-digit Procedure Code (PC) and up to 99 3-digit Additional Procedure Codes (APCs) for a single goods item. This allows for multiple, interchangeable combinations depending on the circumstances and means there is no 1-to-1 correlation between CHIEF CPCs and CDS Procedure Codes (PCs / APCs).