Documents, certificates and Union or international authorisations or other references produced in support of the declaration must be entered in the form of a code composed of 4 alpha-numeric characters, and, where applicable, followed either by an identification number or another recognisable reference. The list of documents, certificates, authorisations and other references and their respective codes can be found in the TARIC database.

National documents, certificates and authorisations produced in support of the declaration must be entered in the form of a code composed of an numeric character followed by 3 alpha-numeric characters (Ex: 2123, 34d5), possibly followed either by an identification number or another recognisable reference. The four characters represent codes based on that Member State's own nomenclature.