LONDON (Reuters) - Britain’s departure from the European Union has triggered the biggest change in trade since it joined the bloc 48 years ago, with companies grappling with export documents, longer delivery times and the need to re-engineer supply chains. Freight volumes moving between the United Kingdom and the European Union were down 38% in the third week of January compared with the same week a year ago, real-time truck movement data shows. Below are just some of the ways in which trade is changing since Britain exited the EU’s single market and customs union on Dec. 31: LONGER DELIVERY TIMES Fishermen were the first workers to be hit in January when the introduction of health checks, certificates and customs declarations delayed the movement of stocks to such an extent that they were rejected by European buyers as no longer fresh. Since then food producers of products ranging from cheese to high-end beef have stopped exporting to Europe for now, put off by expensive health certificates and overwhelming paperwork. Some companies are trying to find a solution. Some Scottish fishermen have taken their catch directly to Danish markets to avoid the British bureaucracy. However about a fifth of small and medium-sized businesses that export to the EU have temporarily halted sales. SUPPLY CHAINS The new friction has forced those companies that can afford it to re-examine their supply chains, particularly those British firms that risk tariffs by selling goods into the EU that were made from materials originally imported from Asia. Online clothing giant ASOS expects a 15 million pound ($21 million) tariff hit because, although most of its European sales go via a Berlin warehouse, some still enter Britain first. Superdry will use bonded warehouses. Japanese carmaker Nissan plans to source more batteries from Britain to avoid tariffs on electric cars. VAT AND COSTS Companies and consumers have received unexpected charges for customs fees, VAT and higher logistics costs that will make some sales prohibitive. Logistics groups said the cost of hiring European drivers to bring goods into Britain had surged. The fact that drivers also need a negative COVID test to leave means the island nation is a much less attractive destination for them. A CBI survey of UK manufacturers showed optimism about their competitiveness with EU rivals has deteriorated at the fastest pace on record. Despite that, EU orders improved, suggesting that EU firms are still sourcing from the UK. FINANCIAL SERVICES Britain’s Brexit trade deal with the EU, in force since Jan. 1, does not cover financial services, leaving its City of London financial centre largely cut off from the bloc. European daily share trading worth 6 billion euros ($7.36 billion) left the City of London for the continent in early January, along with a chunk of swaps trading. That raises questions over the value of any future EU access, given that UK banks and trading platforms have opened units in the bloc. Brussels has said it will not consider granting more equivalence access until a