Deal or no deal, British companies will have to confront a wall of bureaucracy that threatens chaos at the border if they want to sell into the world's biggest trading bloc when life after Brexit begins Jan. 1.

When the U.K. casts off from the European Union, firms that drive nearly $1 trillion in annual trade will have to navigate myriad new rules and red tape that will increase costs just as COVID-19 bleeds the economies of the West.

Outside the EU single market where trade flows freely, the U.K.'s exporters will have to complete a raft of paperwork including customs and safety declarations and navigate multiple IT systems to gain entry to Europe.