Following the correct procedures for goods that require permission before you import or export will help you avoid transport and processing delays and may improve your finances. You can also take advantage of trading schemes known as 'preferences' and 'tariff quotas' which aim to boost trade in certain products and with particular countries by reducing duties. You may need a licence if you want to take part in these schemes.
International trade is heavily regulated for some goods and you should be aware that you may suffer significant penalties if you don't have the necessary documentation, and your goods might be seized by HM Revenue & Customs. Unlawful trade in some goods, such as weapons to countries under sanction, can result in criminal action.