In order to classify your goods you'll need to make use of the Integrated Tariff of the UK - commonly known as the Tariff. This is a large document, containing a product coding system, which provides a comprehensive guide to importing and exporting. You can buy it in binder form or access it online. Volume 2 of the Tariff contains a list of commodity codes that HM Revenue & Customs (HMRC) uses to determine the class under which exports and imports are entered.
The commodity code is a ten-digit number, although an additional four digits may apply to certain products. For imports from outside the European Union (EU), it's necessary to provide the full Tariff classification. For exports the first eight digits are sufficient.
Tariff classification in the EU is based on the harmonised system which defines the first six digits. Although many countries subscribe to the same Tariff classification system, actual classifications may differ.
Read more about how to classify your goods for exporting.
If you rely on the classification from your overseas supplier, you'll need to check whether it's applicable to the UK. The Tariff is published as a whole every year, is updated monthly, is based on EU legislation and is made up of three volumes.