UK: Where can I find Government Guidance for Declaration Entry Information?

Below are some useful Government websites providing information on various areas concerning required data for declarations.

CDS

CDS deferment accounts

CDS port codes

Union codes (produced document codes)

National codes (produced document codes)

GVMS

How to move goods through ports that use the Goods Vehicle Movement Service

GVMS port codes

General

Incoterms and delivery terms