The commodity code - which you need to identify for all interaction with customs - is the most important data field on the Intrastat Supplementary Declaration (SD). This eight-digit number identifies the type of goods which are the subject of a Dispatch or Arrival, and is the basis for most of the statistical information used by government departments, the European Commission, United Nations agencies and businesses.
It is vital to complete this data field correctly. For example, by transposing two digits of the commodity code for unworked precious stones (7103 10 00) you could end up declaring some very expensive cane molasses (1703 10 00). If your particular business trades in precious stones under the chapter 71 commodity code and part of the trade has been entered in the cane molasses heading, neither you, nor those in the cane molasses business are going to get a true picture of the UK's trade.
Commodity codes for all goods are described in the Combined Nomenclature (CN) on which the Integrated Tariff of the UK is based. A simplified Intrastat Classification Nomenclature (ICN) is produced for EU trade, omitting duty and tariff details. You can search for correct commodity codes in the online ICN.
If you need advice on a particular code, you can contact the HMRC Tariff Classification Service by emailing firstname.lastname@example.org.