There is no backlog of goods awaiting clearance by UK customs. The Government has put in place a number of measures to facilitate trade with the EU and to avoid disruption at ports including publishing comprehensive guidance on the new arrangements for trade with the EU and operating a staged approach to customs controls. Until 31 December 2021 most traders importing non-controlled goods from the EU can make a simplified declaration in their own records and defer making a customs declaration to HMRC for 175 days. Further information can be found at https://www.gov.uk/guidance/delaying-declarations-for-eu-goods-brought-into-great-britain.
The Government has also provided a £20 million Brexit Support Fund to support small and medium sized businesses (SMEs) in adjusting to new customs, rules of origin, and VAT rules when trading with the EU.
In addition, businesses can choose to use customs facilitations to make trading across borders quicker, cheaper and easier. Further information can be found at https://www.gov.uk/guidance/check-if-you-can-delay-customs-duty-and-import-vat.